[Closed] Getting best mpg out of a diesel (Golf content)

I wouldn't expect much better than that to be honest without a lot of effort and driving slowly everywhere. A golf emmpty weighs more than 1500kg so theres a lot to shift.

Hmm, I've only ever really driven the bigger VAG diesels and they can be milked a little to get better than that!

As ever, try the whole idea of gaining speed on the downs and coasting as much as you can on the ups. Lay off the cruise control (unless you already have) and just back your foot off the loud pedal by 1/4" or so once you're at the speed you want to be at.

You'll easily get more than that but not until things warm up a bit and stop using the heater, light and such as much it should easily get over 50. I had 3 MK V and they were very good cars and even with less than 12k miles on them I was getting 50+ MPG with ease and I don't drive slow, drive mainly B roads. On long dual and motorway runs it was knocking on for 60MPG.

48mpg isn't great. I get that (or a bit more) out of a heavy Passat with the same engine, and I'm disappointed. It'll do a lot better on summer diesel without the anti-freezing additives in it - I get 52-54mpg in summer.

I'd say for the best results don't do lots of short trips since it'll cause the DPF to get clogged resulting in energy being wasted to clean it out. A good hard thrash at high revs periodically will help with this and many other things.

Whilst driving in town or on country roads, try and use a burst of medium throttle to get up to speed then very light throttle to almost coast up to the next corner or light. This makes a big difference. If you have a manual take a tip out of the auto's book and don't take the revs above about 2krpm unless you are in a hurry. Simlarly don't go below about 1.2krpm either, it doesn't help. Be mean with the time you are pressing the throttle not how hard you are pressing it. But don't be mean with the steering wheel. Cornering harder means keeping the speed up and therefore less acceleration and wasted energy.

You should be seeing over 50 in winter and high 50s in summer I'd say, at least. Make sure the tyres are up to pressure too.

My current Mk VI has cruise control, I get way more if I use that than I do when not using it.

I'd say use cruise control - it stops your speed creeping up when you're not watching the speedo or the fuel economy readout - which ruins mpg.

Oh it's a GT TDi - that explains a bit. Larger turbo means more back pressure I'd say - so 48 is fairly reasonable. Could still do better tho 🙂

All mine were GT TDi 140s, great cars.

I use my cruise control quite a bit too. Only problem is going up hills on the motorway when it wants to keep banging on at the same speed. I always think what it would be like if I was pedaling and tried to ride up the inclines as fast as on the flats. Its all about constant effort not speed.

Oil change between services helps keep it all healthy which has to be a good thing as does letting the car cool slightly from motorway level exertion before turned off.

Cheers guys. Don't think it's got a DPF so that's one less worry. No cruise at the moment but I'm going to get it fitted as I do like it. I've read about the winter fuel consumption thing and am already looking forward to spring!
I'll try to be a bit gentler with the accelerator but I don't want my trips to take forever, and it is a GT after all 🙂

You'll find there won't be a huge difference in fuel consumption anyway between welling it and taking it easy. My consumption has dropped massively on my current one this winter as the kids or Mrs are usually in so heaters are on a lot. Plus most of the driving is in early morning evening so lights are on too, that said the newer one has side lights in all the time anyway.

I've got a MK4 golf gt tdi 130 and I can just about get 50mpg if I drive like a granny! Usually 42mpg on the commute from Swindon to Taunton which is 90% motorway.

My vagcom cable has turned up so I'm going to test the MAF shortly and looking at cleaning the inlet manifold out as it's done 125k miles.

Like a golf but not a golf,Just because its got a set of golf clubs on the back seat doesnt make it a golf.

I'm intrigued... surely the heater doesn't use any more fuel?

The engine produces the heat anyway, surely having the heater on just means it goes into the car instead of out into the air through the radiator?

My 1.9 Tdi A3 normally knocks out 49-53 mpg whilst doing the school run twice a day, a trip to supermarket 3-4 times week and 100 mile round trip to work 3-4 times a month, so I was horrified to fill up today and calculate that my last tank worked out at 42 mpg...... Must be the winter and I must check my tyre pressures tomorrow as that's one thing I rarely check!

[i]The engine produces the heat anyway, surely having the heater on just means it goes into the car instead of out into the air through the radiator? [/i]

It's climate control and still need power to push the air out, gone are the days of it trickling through on it's own steam.

Have another fuel strike. Empty roads and frugal driving = 65mpg in my old Golf 130TDi. Boring though.

Only problem is going up hills on the motorway when it wants to keep banging on at the same speed.

Nothing wrong with that. Probably does not use more fuel. Ok so it's working harder but not for as long. At the same revs (ie in the same gear) there's probably a similar proprtion of heat lost through the exhaust I'd guess than if you were driving on the flat, so then it should boil down to more fuel being input being cancelled out by being going up hill for less time.

As for using the heater - doesn't matter much when you've been driving for a while because the heat is being wasted.. the power required for the fan is minimal. However if it's really really cold using a lot of interior heat can mean that the engine is actually under temperature.. or if it's short trips then the engine takes longer to heat up. Although the impact of that on a diesel is probably much less than petrol.

I've got a 130 Mondeo TDI. I'm driving roughly 500 a week at the min on motorways.

Doing about 60-70mph I get around 51 mpg

Doing about 80-85mph I get 49 mpg.

The things that I have found make most difference are not having air con, heated windscreens etc on (as much as 5mpg). Under inflated tyres 3-4 mpg. Posh fuel 4-5 mpg. Cruise control doesnt make any noticable difference on my Mondeo.

Driving like a nutter I can get the average down to about 43mpg.

If your car isnt new to you, make sure your drive it quite hard for a little while ie reve it quite hard. It will loosen the engine up (if it wasn't already) and improve the mpg.

Just a few notes on my own diesel:

IT has not only glow-plugs to power (both pre and post start at times), but also water heaters, yup, thats right it has fast-heat water heaters to get the engine up to temp fast - I've not decided if this helps or hinders efficiency yet!

Banging at same speed seems to be most efficient in mine, slowing up hills and accelerating back to speed down hills seems to add a tad onto my fuel use. I'm not sure that's logical, but the difference is so small it could well fall within normal error bounds so isn't really worth worrying about.

Biggest killers are changing speeds (accelerating is taking LOTS of energy, braking just means you wasted the kinetic energy you had). Keep blowers to a min, turn demister off as soon as screen cleared, don't leave it to go off by timer.

Probably the most important - check tyre pressures.

It will loosen the engine up (if it wasn't already) and improve the mpg.

If my engine loosened up when I drove it hard I'd be worried. About all you'll do is clear some of the junk out of the intake and exhaust system, you wont make a jot of difference to the bearings/rings etc.

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driving with the flow of traffic Porlock to Taunton in my Skoda 1.9td. I do lots of fuel use testing on cars at work and I am pretty good at getting factory/book figures.

The 2007 GT TDi doe snot have a DPF. The Mark VI version does.

Best way to get better mileage is too adjust your driving style to the more torquey motor.
Keep revs below 2000rpm, you don't really need more than that anyway.
Cruise control is great for the motorway but leave it off in the country lanes.
then the usual change gear early works too.

other than that, not much more you can do. driving style is the biggest contributor

Did you know you can also fill up the expansion tank inside your fuel tank (VW), to give you extra range?

Not advisable if you are planning to leave the car for some time or if the temp. varies obviously, but for a planned long trip, you can add an extra 5+ Litres to your top up.

Just give the switch just inside the neck of the fuel tank a nudge with the fuel filler nozzle and you will hear it vent.

😉

Knottie, that does not impress. If it was a regular tank average it might 🙂

CK - a technical question: In a cold petrol engine the mixture needs to be rich to encourage relibale combustion when the spark goes. Surely in a diesel this is not the case? In my old fully mechanical Passat the cold start handle advanced injection timing and raised idle revs but it did NOT add more fuel. So surely one should conclude a cold diesel does not use more fuel than a warm one, but a cold petrol does...? The mpg in my diesel is always very low for the first 5-10 minutes but I think that's due to having to drive very slowly up a steep hill then sit in traffic for a bit before hitting the open road. What do you think?

[i]nottie, that does not impress. If it was a regular tank average it might[/i]

Or me, my current record on an 18 miles steady drive is 93mpg.

the best way to save fuel is to learn how your car uses fuel by watching an instantanious comsumption gauge and adapting your style of driving to suit. My average over the last 700ish miles is 67mpg btw.

I find those gages to be miles out showing 200mpg+, that and sitting watching that to get your best miles means you'll probably not get too far.

"I find those gages to be miles out "

yes but they do give you an indication to learn from.

a technical question: In a cold petrol engine the mixture needs to be rich to encourage relibale combustion when the spark goes. Surely in a diesel this is not the case? In my old fully mechanical Passat the cold start handle advanced injection timing and raised idle revs but it did NOT add more fuel. So surely one should conclude a cold diesel does not use more fuel than a warm one, but a cold petrol does...?

Technically, I THINK (though I don't know for sure) you're right, but in practice I don't think it works out quite that way...

I notice I don't get quite the same fuel economy through the colder months in my Golf TDi as I do in summer. Which I think is probably more due to the heater being on a lot more, and possibly extra additives in the winter fuel.

Also remember that if the engine and gearbox oil are taking longer to warm up, that's more friction. Hence you will be pressing the accelerator pedal slightly longer and harder than you would if all the oils are warm, ergo using a little bit more fuel.

Oh, and for those who doubt, cruise control in many modern cars now is actually more fuel efficient for most people than driving without it. From my experience of recent cars fitted with cruise control, it seems to be much happier to allow the car to "run on" a little bit if it creeps over the speed, and is a bit less eager to react if the speed drops slightly under the prescribed speed. Compare that to cars say 10 years old with cruise control, that in many/most cases would snap the throttle shut if the speed crept up by 0.5mph or open it wide if the speed dropped by 0.5mph, and you got a much more "kangaroo juice" effect.

My 57 plate BMW 320D I had as a company car 18 months ago would achieve quite amazing economy (considering its size and 177bhp potential) at a steady 70mph on the motorway with the cruise control on. 65-70mpg was easily possibly. Put the cruise control on at 60mph for a stretch of dual carriageway once for maybe 12 miles. Over that 12 mile stretch it achieved 72mpg! OK, a smaller lighter car would have done even better, but this was a 1500kg family saloon with 140mph top speed and 0-60 in under 8 seconds performance!

I find those gages to be miles out

Only true accurate way to measure your MPG is of course to capture your milage and the amount of fuel used every single time you refill.

The few BMW's I've had over the years (old and new) have always been within 2-3% either way on the fuel economy computer on the car. That's not mega accurate granted, but it's close enough! It could also be the difference in human error when refilling the tank, perhaps not quite brimming it as high as you did last time... 😕

as said use cruise control, turn off as much as you can and shop around for best deal on fuel as that will be the real cost saver

Mol - as far as I'm aware you're more or less right, certainly with the older D's (Before common rail) timing was about the only thing they altered.

Take 2 un-controlled controlled D engines to one side, one hot, one cold. The cold one will have larger losses due to viscosity of oil and possibly require different timing of the injection to allow a full burn with a more viscous fuel. Once you introduce idle control to it though, you have different situations - timing, fuel and temp and RPM all interact, if you want to hold the same idle you could add more fuel or change timing, until some limits when adding more fuel just drowns the engine as the timing is off, likewise you could change the timing but within limits. But often you'll raise RPM slightly so that may require a little more fuel OR more advance, OR a bit of both. I suspect modern injected Ds work with both variables to maintain idle speeds suitable for the temperature.

In essence I think that with old hardware you might just be running with poorer economy to start, with more modern engines you can run at high efficiency and frugally when up to temp, but cold engine still requires what was effectively "normal" running on the old lump. Add that to the fact that you're crawling slowly and possibly also running water heaters and window heaters and headlights off the alternator, you're bound to get low mpg to begin with. The dash gauges are notoriously unreliable, some are taken off calculations from injection pulse width and current speeds etc, some just come from rpm, throttle position and time after start etc. In a modern ECU there are usually upward of 7 30+x30+ cell tables calculating your fuel based on sensor inputs, so it just depends which info was included. Fueling and timing calculations include variables like coolant temp, air temp, revs, manifold pressure/air flowrate, knock feedback, time after start, battery voltage, fuel pressure, rate of throttle increase/decrease, and several of these scale by each other, so more fuel would be added with the throttle-rate variable if it were done cold instead of warm etc

[i]Only true accurate way to measure your MPG is of course to capture your milage and the amount of fuel used every single time you refill.[/i]

The average MPG ones seem very accurate, the current MPG ones are or appear very random.

Actually.. the thermal efficiency of the expansion would be worse if the cylinder walls/piston were cold since some heat would be travelling into the metal/coolant. Also if it's colder in there combustion would not be as complete (even my newer DPF diesel smokes more on startup), so overall it would seem to be running less efficiently hence requiring more fuel to achieve the same driving...

Another question: in winter, a diesel should be more efficient because the intercooler would work better, right? Resulting a colder charge in the cylinder? If it weren't for winter diesel, and snow/standing water notwithstanding, you should get better mpg the colder it gets...

Only true accurate way to measure your MPG is of course to capture your milage and the amount of fuel used every single time you refill.

The pumps at petrol stations are way inaccurate, as are the cutoff valves. So when you see a discrepancy between the gague and the pump reading, it's the gague that'll be more accurate since it's computer controlled precision electronics, not a wheezy old mechanical thing.

My 57 plate BMW 320D I had as a company car 18 months ago would achieve quite amazing economy (considering its size and 177bhp potential)

That's the beauty of diesel. You only inject in as much fuel as you need to move the car, and to make a performance car you just need to put in more air and fuel when you bury the pedal. In a petrol you have to inject in enough fuel for it to ignite under spark, and then use the throttle to drag the engine back to the speed you want, which is very wasteful. That's why performance petrol cars are very uneconomical, but performance diesels can be nearly as good as normal onces. Only the size of the turbo and the weight of the larger engines drops the economy a bit in faster diesels.

It's also why a remap to higher power doesn't affect economy in a diesel. It can even improve it due to better torque allowing higher gears to be used.

Quick note to those going on about hills:

Simple physics will tell you that it makes no difference. The amount of energy required to lift the car the required height is the same no matter what speed you are travelling at.
Since most of your energy is expended fighting air resistance and mechanical friction, it's really only your average speed and gear ratios that matter.*

*that's not to say that hills don't increase your fuel use, they do of course, but how fast you go up or down them doesn't make any difference (or rather no more difference than it would on the flat).

Yup, the delta-T would be higher for a short while.

Not all TDs have intercoolers, but your temp difference would be give better cooling. D's run lean to idle (you don't match fuel ratios like in a petrol) so if you have more dense air it won't alter the amount of fuel required to idle at a set speed, but the air will expand a bit more with the explosion so may slightly reduce the required fuel in that sense. I'm not convinced it'd be more efficient overall (due to cool engine, longer warm-ups etc).

Simple physics will tell you that it makes no difference. The amount of energy required to lift the car the required height is the same no matter what speed you are travelling at.

It's not quite that simple though, as you allude to. The actual amount of energy used will depend on drag, drivetrain losses, engine maximum efficiency point, whether or not the hill gets long and slow enough for you to need to put your foot down anyway, and whether you need to lift off completely on the down side.

Petrol pump delivery measurement is pretty damned accurate BTW, they're displacement measurement rather than your car which guesses at how much fuel the injector allowed through, not accounting for blockages or wear. Figures I've found for the petrol pumps are -0 and +0.5%. Having seen fuel injectors injecting ~15% more than they're rated at, and with fuel pressure regulators having a level of inaccuracy too, I'd suspect the fuel pump was more accurate. Though whether you can top it off to the same point or not is a different matter.

my "MKIV GT TDI PD 115" got 48mpg driving at 60mph all on motorways for 140 miles except for 10 miles of the journey, in the winter.

Lights off, aircon off, heater/fan set to position 1, stereo on. I check the oil and coolant etc. regularly.

Not sure if theres something wrong with it or its just what happens with the winter fuel?!
I'm pretty sure it'd cost more to fix than i'd ever save in fuel though.

That's why performance petrol cars are very uneconomical

Fifth Gear tested the recent Porsche 911 and got 30 mpg out of it, and i think it had well over 300bhp.

Yes, but its fairly easy to get 50+ mpg and 300 hp out of a diesel. I can easily get 28mpg from my 300hp 2litre 4x4 petrol on a run, but likewise I can get as low as 17mpg just knocking about and I'd get nowhere near the 60+mpg my 2litre TD gets. We are comparing apples and oranges though, ultimately a performance D has no throttle losses and can potter along fairly nicely with very little fuel despite having huge potential.

[url= http://www.cararticles.co.uk/uk-the-trident-iceni-%E2%80%93-a-70mpg-supercar.html ]Try a 6.6 litre Diesel supercar that gets 70mpg[/url]

crikey, what car does that??

Simple physics will tell you that it makes no difference

Simple physics yes, not the complicated real world physics of engines 🙂 When you drive a car harder that may mean lower gear and/or more throttle. So that means more losses, more heat loss, more unburned fuel exiting the exhaust, not to mention the effects of variable valve timing and about a million other things.

As for diesel/petrol in terms of performance and economy, check out the Audi TT diesel and petrol versions. Same car, very similar performance, very different mpg.

And whoever quotes 30mpg as an example of good fuel economy is living in the 60s aren't they? 🙂

i used to often get 55+mpg average on one tank in my old ('98) Seat Ibiza 1.9d. used to check what went in at the pump against how many miles i'd driven.

that included relatively short trips and use for work (i.e. rush hour).

As for diesel/petrol in terms of performance and economy, check out the Audi TT diesel and petrol versions. Same car, very similar performance, very different mpg.

40mpg vs 50mpg

People seem to overstate the difference between diesel and petrol.

30mpg used to be what you'd expect from a 1.6 Ford Escort, not a car with 340bhp that does 178 mph. Point being, petrol engines have improved too.

im pretty sure you already new the answer to the original post when you started the topic...you just wanted to brag about your diesel which every1 already has...

On average i get the same as the op from the same motor. You can thrash it and get about that or you can be very frugal and get 58mpg but it is only recommneded if you have the time and patience.

Been clocking fuel consumption on my latest for the last 5yrs and turned in repeatable results over this time, and for the last year i've taken to switching the engine off when waiting in traffic and at lights. Since doing this i've got an extra 2-4mpg every tank.Apparently it's something the Germans do as a matter of course, and car manufacturers are now automating.

[i]I find those gages to be miles out showing 200mpg[/i]

They work both ways, as I've proved with my Passat. 1st time it said summing like 49.7 when in reality it was 47.9 then on a trip to Ft Billy last year it said 52.2 but on filling up at Morrisons in Ft Willy it was actually 53.7.

The torque on my Toyota Verso doesnt really climb until around 2000rpm, I was under the impression I would be better keeping the engine above this rpm as the engine is producing more torque for a given amount of pedal movement, than keeping it below where I need to press the pedal more as it is underpowered. But some of the posts above about staying under 2000rpm make me question whether Im right.

Though it is very dull to always change gear before the turbo spins up. I usually keep the revs between around 1500-3000rpm.

The torque on my Toyota Verso doesnt really climb until around 2000rpm, I was under the impression I would be better keeping the engine above this rpm as the engine is producing more torque for a given amount of pedal movement, than keeping it below where I need to press the pedal more as it is underpowered. But some of the posts above about staying under 2000rpm make me question whether Im right.

Though it is very dull to always change gear before the turbo spins up. I usually keep the revs between around 1500-3000rpm.

Is it petrol or diesel?

And if it's a diesel, are you sure it's the torque or the power you're noticing? Power of course being a multiple of torque and engine speed.

Most diesel engines produce their peak torque at below 2000rpm these days, but it should also be noted that the peak torque is the point in the rpm range where you are getting the most complete burn of the fuel in the cylinder per revolution. Not necessarily the point where it's using the least fuel... OK, sorry, perhaps not the best explanation, but whilst using a diesel's strong torque to accelerate it quite quickly but without revving to high (where the engine becomes inefficient) is more efficient than in a petrol, but may also not be quite as fuel efficient still as trickling it very slowly along, changing gear before the turbo spools up even.

Unlike in a petrol engine, the amount of diesel squirted into the engine by your injectors is directly proportional to how hard you press the accelerator. So tickling it gently of course will yield the best results. Accelerating hard before the turbo spools up will of course be very poor for your fuel consumption, as you won't be accelerating very much (because of lack of turbo pressure) but you're still using lots of fuel.

Driving a diesel for optimum economy is a trial, as it requires some quite different approaches depending on your speed, engine speed, incline and all sorts of other variables. Driving a petrol for maximum economy is much easier, as you just need to lay off the loud pedal as much as poss... That said though, of course a diesel will give you much better economy anyway!

Fifth Gear tested the recent Porsche 911 and got 30 mpg out of it, and i think it had well over 300bhp.

I remember Gordon Murray saying about his own McLaren F1 (he designed it by the way for those that don't know) that he used to get 26mpg whilst cruising down the motorways at "normal" traffic speeds (ie. 75-80mph). That's with a 6.1 litre V12 that produced 627bhp! Might've had a fair bit to do with the F1's low weight of just over 1100kg though in fairness...

Have had 32mpg out of a 1995 4 litre V8 Beemer 5 series myself on a 70 mile run before... That said I'm sure it was much easier to achieve 30mpg out of a new Porsche though, seeing as they have direct injection and are pretty efficient for a modern large capacity petrol engine.

[i]They work both ways, as I've proved with my Passat. 1st time it said summing like 49.7 when in reality it was 47.9 then on a trip to Ft Billy last year it said 52.2 but on filling up at Morrisons in Ft Willy it was actually 53.7. [/i]

I'm not talking about the average ones, I was quoting a reference to the constant ones.

Rich - the slower the engine speed the more time the fuel has in the cylinder to combust properly. However getting the same power As for changing before the turbo spins up, that must be a bad idea. The car often overfuels in order to get the turbo spinning, so you might well be pouring in fuel without enough air which would be wasteful.

As for the Audi TT, as far as I can tell it's 37mpg for the petrol combined and 53 for the diesel. That's a fair difference in my book. It means, based on a 45 litre tank, another 160 free miles each time you fill up, or 45% extra. Not bad is it? And that's the cutting edge highly efficient TFSI petrol engine which is about as good as it gets for petrol.

As for your Passat gague showing 200mpg, that's your instantaneous mpg at that very instant ie when decelerating or going down a hill. If it says 200mpg for a whole trip then it's got something wrong with it 🙂

got a 55 plate Golf GT TDi and i can get 65+mpg on a slow motorway drive. Average about 56/7 though even with a heavyish right foot.

If i want to be frugal then it's AC off, and change gear just as you reach the top of the torque band when accelerating (about 2300RPM i think) There's little reason ever to take an engine with that much torque over 3000 RPM, also stay in a high gear when braking for as long as possible until you feel the engine management fighting back, try to go to neutral at the latest possible point. You get best result by driving smoothly, taking corners well without changing speed much and by thinking a good 1/2 mile ahead on the motorway so you don't have to change speed

on my passat i've found that cruise control uses more fuel on the motorway as it's not intelligent ie it doesn't see changes in the grade of the road so doesn't pre-empt hills. I get 3-4 more mpg if i leave cruise control off (it's a 1.9 PD130 though)

What I like about the Golf is that you can hammer it a bit and still get decent mpg

Hi, yeah I have a power/torque graph for my car and peak torque is from 2000-2900rpm, with it starting to climb sharply from 1600rpm, with peak power at 3600rpm, so I try and keep the car within the 1600-3000rpm range generally, going up to 3600rpm when overtaking.

I have tried accelerating really slowly and it is worse for MPG than accelerating fairly quickly then tickling the pedal once up to speed.

I suppose it is slightly different for each car, though I have heard how it isnt good for modern diesels to never be revved, leading to a build-up of too many sooty deposits, especially if the car has a DPF, so opening up the engine once warmed up should do them some good IMO.

Good topic. 🙂

I suppose it is slightly different for each car

Depends on the engine really. The fabled VW PD engine is the one with a massive slug of torque early on and then nothing in the high range, and it's been used in loads of cars for many years. Common Rail engines are much more like a small turbo petrol as in they take off well but keep pulling up to the line. This is because in a PD engine the injectors are actuated by the camshaft which only allows limited variation in injection timing.. whereas common rail has total control and can advance it a lot at higher revs.

I have tried accelerating really slowly and it is worse for MPG than accelerating fairly quickly then tickling the pedal once up to speed.

This is true, especially in my Prius or any other car with a CVT, particularly petrol, because by accelerating at middle ish throttle your revs are in the most efficient band ie about 3-3.5k (for petrol).

im pretty sure you already new the answer to the original post when you started the topic...you just wanted to brag about your diesel which every1 already has...

😯

I presume that was some kind of joke. If not, then thanks for your input. I have actually learnt some stuff from this thread (especially about you)

[i]on my passat i've found that cruise control uses more fuel on the motorway as it's not intelligent ie it doesn't see changes in the grade of the road so doesn't pre-empt hills. I get 3-4 more mpg if i leave cruise control off (it's a 1.9 PD130 though)[/i]

Same here. I can build my MPG up to about 50+ but as soon as I switch to CC it starts dropping.

Weird I thought diesels did more (depending how heavy your lead foot is) but I'm getting 40+mpg out a 2 litre petrol car?

(Getting bugger all in city driving 25mpg?)

Though that van thread has been giving me ideas for a diesel next.

[i]Weird I thought diesels did more (depending how heavy your lead foot is) but I'm getting 40+mpg out a 2 litre petrol car?

(Getting bugger all in city driving 25mpg?)[/i]

diesels get 40mpg+ in the city as well