How to improve fuel efficiency of a car…

Reduce the weight it’s lugging around.

Make the wife/girlfriend walk.

Drafting lorries saves tons of fuel
I had 103 miles in the tank and 110 to drive
Made it home with 20 miles still in the tank

Bout 5%, best case, sometimes 3-4%

Sorry wasnt suggesting you shouldn’t get them just you could start with bigger and free gains from driving style.

That longevity has to come from somewhere. What’s the grip like when it’s lashing down? Read a couple of reviews and heard others moaning that they don’t bite well in bad conditions. Personally I’d rather skip the economy tyres and go for enhanced wet grip of that’s the case.

Got my 3l diesel (160,000 miles) Terracleaned.
Definitely quieter afterwards, seems smoother.
During the process he kept having to reduce the brace holding the throttle open as the injectors were cleaned, seemed to work.

I’ve been averaging about 32mpg on BMW 530d touring, mostly round town driving but getting up to 40mpg on a motorway journey.

Mostly it’s down to learning not to use all the power if you want the mpg to go.up. Personally I’d rather make use of the power occasionally and pay at the pump.

What’s the grip like when it’s lashing down? Read a couple of reviews and heard others moaning that they don’t bite well in bad conditions

Never had a single issue. I test emergency stops frequently. Early energy savers were poor in the wet, not so now. The Nokian summer tyres were the best I’d ever used hands down, regret not going back to them this time around.

The tyre compound is the same stuff bike tyre makers use, continue call it black chili I think. The reason they roll better is that the addition of silica changes the vibration properties. Less resonance at high frequencies (which affects RR). They aren’t simply harder compound. I don’t know why they last so long, but the rears on the Passat were about half worn at 40k. Had to change them elbecayse they sawtoothed on the inside edge due to a broken spring.

Worth noting that the ones that come as OEM on cars have the same names as production tyres but aren’t anywhere near as good, leading people to conclude they are bad tyres.

Unless there’s something actually wrong with the car, outside of what you’ve already done I don’t think you’re going to see any noticeable returns. It’s amazing the difference something can make though. When my exhaust was blown, I dropped from about 35mpg to 25mpg! Which is a big hit at the pumps.

If my understanding is correct, modern engines can shut the fuel off when coasting in gear because the car’s weight keeps the engine rotating not the combustion cycle.

Yeah, the only situations where coasting in neutral is potentially going to help, is when coasting in gear is going to slow you too much. You’ll generally need to be above a certain rev range to hit the fuel cut though. I think mine is about 1.75krevs.

I did experiment this in my car. Where I went through a few tanks of fuel driving like an absolute saint. Well, not a saint, because I don’t think coasting in neutral is considered safe practice. But using at a guess, never any more than 10% throttle. Coasting neutral wherever possible. Never exceeding 60mph. They were the most boring weeks I have spent driving in my entire life. And it turned out the fuel economy was no better than normal driving…

If you think ahead, maintain a steady pace, slow gradually and rarely use the brakes….you can still floor it to get up to speed occasionally and still maintain excellent fuel economy I find. It’s the constant stop/start in the middle that will burn the fuel.

One thing that I’ve found over the years, is that a warm car will return much better economy than a cold one. If you only ever do trips of less than 10 miles, doesn’t matter where you drive it, you’ll not get the economy you’re hoping for.

And it turned out the fuel economy was no better than normal driving…

I can get about 10% extra by trying hard. But not actually using a lower top speed.

On windy roads, mid throttle then ease off with as few blips as possible. On DC’s and motorways, cruise.

http://www.theregister.co.uk/2014/10/19/crawling_from_the_wreckage_essay_making_cars_more_fuel_efficient

Tweaked a Jaguar XJS and now gets 43mpg out of a 3.6l V6 petrol engine….

Some pretty wild ideas in there but could be a lot more fun than just coasting up to traffic lights.

Have you tried one of those magnets that goes around the fuel line?

some basic advice to try first which will definitely help either fuel economy or reliability

1. service the car – either you or garage, do all filters and check tyre pressures are correct.
2. reduce weight by removing unneeded items from car
3. use “acceleration sense” – every time you press the brake pedal you are costing yourself money by wiping off speed that you paid for in fuel to build up – try and anticipate so you use the brakes less and use engine braking more.
4. avoid shorter journeys – a 3l diesel is a fair lump of iron to heat up, this will cause reduced economy of short journeys compared to long ones

olddog
I think you need to coast in gear. That way the wheels drive the engine and uses no fuel. If you press clutch or take out of gear the engine needs to burn fuel to idle

Only if you want to stop.

The highest possible economy is gained from coasting in neutral, because that reduces the total powertrain loss, ie for every turn of the wheels the least amount of energy is lost. However, if you need to stop at say some lights or a roundabout, then using overrun braking from the engine will deccelerate you with the least fuel penalty. For ultimate economy don’t stop, because your car can’t recover the KE stored in its mass at speed. (even an EV / hybrid can only manage to recover roughly 50 to 65% of that energy due to system inefficiencies and limitations)

Shouldn’t need to work a 3.0 turbo diesel too hard, just need to avoid ‘making progress’.

Mechanically, fuel filters are often over looked, injector cleaner like BG244 and a bit of Italian tune up. EGR delete to stop dirty air going back in. Back box dropping off the Mondeo led to an improvement in mpg, had to fit one for MoT and mpg dropped again.

Have you tried one of those magnets that goes around the fuel line?

If only manufacturers fitted those as standard 😆

That seems reasonable. I’ve driven the M4 between Cardiff and Reading hundreds of times since I got the Passat – first time out I got 48mpg, then it kept going up and up to 55mpg, then I got eco tyres, and my (repeatable) best is about 62mpg. No idea why it went up gradually like that.

Sitting tight in behind the trucks and not overtaking perhaps? 😉

Someone I know on this forum has fitted a sump heater to his car as it does short journeys. Common in Canada etc.

Plug the car in and the timer heats the oil up before you start the car, obviously there is an upfront cost but once thats done, I bet the electricity used to preheat would easily be covered by much better economy during the first 5 miles.

Even better if you can get away with using a second lead to preheat at work as you get the savings on the return journey too 😉

(edit, and yes, they do commute by bike sometimes too…)

I agree with pretty much everything so far. Nobody has mentioned getting the tracking checked though ? That could possibly suck a bit of fuel if it’s well off.

To the OP – what makes you think the economy is poor ? If it’s in line with other people’s experiences with the same model then there’s probably not much you can do to the car, it’ll all be about how you drive it.

My car reliably returns about 53mpg (calculated) on 400+ miles a week along the M3 & A303. I once managed to get 60mpg by dropping the speed to 60-70 instead of 70-80. That’s a lot more than I’d ever exepect from a tune-up. But it got frustrating getting mixed up with all the trucks and the diminishing returns thing kicks in; saving four quid a week just didn’t feel worth it.

think ahead, maintain a steady pace, slow gradually and rarely use the brakes

them ones, i.e. accelerating as rarely as possible, and retaining as much kinetic energy as possible. some people are crap at this, always on the accelerator, always on the brakes, always up the arse of the car in front, their fuel economy will suck… travel outside of rush hour

and driving slowly, cause wind drag and all that. again, some people are crap at this, got to travel at 80+mph

All this talk about saving fuel, I prefer to enjoy my driving and not stress about it. With a 425bhp + 4WD estate then 25mpg on a long run is pretty good going, but to be honest I’d rather drive the thing as intended so normally it hovers around the 19mpg average.

The accounts guy in work was bragging to me the other week about how his new Passat got him over 60mpg on his daily commute, followed by the question “what do you get from your car then?”

I was tempted to say “laid”, or “a hard on” but instead bit my tongue and simply said to him “a smile”.

Honestly mate, you to work on that. Not everyone wants the same things from a car. Please don’t look down on those of us who aren’t into lots of power and vroominess.

Just because you can’t understand it, doesn’t mean it’s without merit.

Give it a good polish to reduce the wind resistance……………

Be interesting to hear what engines & cars people have when they’re giving us their MPG.

One thing that might be worth a go is to disconnect the battery for 15 mins. Returns the ECU on a modern car to its factory baseline and re-learns. It might help, it might not.

2.0 TDI 140ps auto here.

was tempted to say “laid”, or “a hard on” but instead bit my tongue and simply said to him “a smile”.

you get a hard on from a car, thats v sad.

you get a hard on from a car, thats v sad.

Haha, it was just a joke 🙄 Seriously though some of us choose to enjoy life and whist you’re sat there worrying about whether your car does 52 or 54mpg, the rest of us are out there actually having fun 😆

“Be interesting to hear what engines & cars people have when they’re giving us their MPG“

Bangernomics BMW E46 320td Compact. 15 years old and nearly 170k miles. Easy motorway journey of 40 miles each way results in 53mpg as calculated from fuel receipt. The OBC is *wildly* optimistic and usually reckons 70+ mpg 😆

41 mpg brim to brim out of my 1.9d tractor engine. Doesnt seem to care if its through town or on the motorway empty or loaded with a 3.5litre v8 and gearbox in back…..

Get 32mpg brim to brim out of my 200tdi 90 if i stay below 50 or dont drive through town above 50 and the fuel gauge moves down fast

Seriously though some of us choose to enjoy life

So do I! I just drive sensibly! There are lots of ways to have fun, don’t you know. And I don’t actually worry about the 2mpg, to the extent that it has a negative effect on my life.

EGR delete to stop dirty air going back in.

Don’t do this, the EGR’s there to stop the engine producing NOx, that ‘dirty air’ is no worse for the engine than the nitrogen in the atmosphere it’s designed to replace.

NOx results in respiratory illnesses, has direct impacts on plant growth, forms particulates in the atmosphere (smog), produces Ozone and leads to acid rain.

Basically it’s one step short of saying;

Club a baby seal to death, strip off the blubber and render it, then put it in the fuel tank, it saves you money

whist you’re sat there worrying about whether your car does 52 or 54mpg, the rest of us are out there actually having fun

I dont worry about 2mpg.
I dont think about cars much at all, more likely I am actually living than knocking one out over a bit steel and plastic.

thisisnotaspoon – Member

EGR delete to stop dirty air going back in.

Don’t do this, the EGR’s there to stop the engine producing NOx, that ‘dirty air’ is no worse for the engine than the nitrogen in the atmosphere it’s designed to replace.
From what I’ve read EGRs can cause acidic engine oil, earlier degradation of the engine oil, lower MPG and reduced power. All things, that whilst the NoX is reduced, all potentially can have a negative impact on the enviroment i.e using more oil, petrol etc.
Plus my EGR keeps screwing up, so I’ll be blocking it off when I get round to it. Whilst its a selfish attitude, I hardly think my pissy renault 1.5 dCI engine is the worst polluter out there.

From what I’ve read EGRs can cause acidic engine oil, earlier degradation of the engine oil, lower MPG and reduced power.

I think you’ve been reading petrolhead complainings. Let me respond:

1) Lower power – when you floor it the EGR valve shuts, always has done – so does not affect full power. In fact, it doesn’t take that much throttle to shut it.

2) Acidic engine oil – not sure about this, but a lot of combustion products end up in the engine oil anyway via blow-by, so I doubt this has an effect. All it does is put combistion gasses back into the intake charge, and when you burn it it’s still just combustion products – can’t see what the problem is. Plus, every diesel has had this for 20 years or so, and when we see diesel engine failures it’s generally not big ends or valve stems or any of the things that would be cause by poor lubrication.

3) Increase MPG – as I said it only operates at low throttle input so maybe if you are tootling around town – but then the fuel economy is rubbish anyway. The EGR on my car wasn’t working for ages (it was closed) and I did get some good fuel economy figures, but I was doing a different regular trip. On the M4 trip I’ve done most often, I think the difference might’ve been 63mpg vs 62mpg or so, but that those numbers it’s quite hard to tell.

If you have a Passat you can unplug the EGR valve actuator and see what happens – it’ll stay closed so you’ll get no EGR.