[Closed] Petrol vs Diesel

You mean you want something faster which would be too thirsty in petrol form?

Sort of.

But at the end of the day I want an Alfa. A red one. That's all. Simples. 🙂
I don't really want a diesel. If it was for me alone I'd have a 3 litre V6 or 2 litre twinspark.
But there's more than that to consider.

Although, that said, I'd rather spend £3000 or less on a nice v6 or TS than double that or more on a newer diesel
Diesel in an Alfa is like a moustache on the Mona Lisa. But we won't go there, eh? 😉

There's a decent 1.6TS 156 for sale near us for £600 actually. That would do me if it wasn't blue.

My tuppence after having to endure 600miles in a diesel this weekend.

Petrol - floor it and revs x torque = power; simples! If you try and set off from 20mph in 5th of course nothing happens, knock it into 3rd though and shit leaves the shovel.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise. This is a product of slightly more efficient combustion and the above mentioned turbo lag means that airflow is only vaguely correlated to what your right foot is doing, if you built in throttle response that slow into a petrol ECU it'd probably be efficient too.

[i]Petrol - floor it and revs x torque = power; simples! If you try and set off from 20mph in 5th of course nothing happens, knock it into 3rd though and shit leaves the shovel.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.[/i]

you need an auto Mate

Or needs to learn that diesels are not petrols and petrols are not diesel......

Drive em differently .... Diesels are lazy mans cars. Petrols are for folk who like changing gear

thisisnotaspoon - Member

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

Try some better diesels.

Also, an observation... Sometimes I do need to knock mine down a gear or two from cruising to overtaking. The reason for this is that it can cruise along at about 1200rpm. Now that's not a "problem" you'd have with an equivalent petrol car, because it wouldn't let you do that in the first place- you'd have to be carrying more revs.

Thing is though, this is an extra capability that you don't have to use- nothing to stop you driving a diesel up in its power band, at which point you'll have more immediate response.

O[i]r needs to learn that diesels are not petrols and petrols are not diesel......

Drive em differently .... Diesels are lazy mans cars. Petrols are for folk who like changing gear.[/i]

Get a 3 litre V6 petrol and there's not a lot of gear changing required. Unlike the wifes V50 Sportwagon 2.0D which is okay, but you gotta be in the right gear.

Recently bought a passat diesel, and engine responds very nice indeed. Got to love diesels. Oh and it purrrs like a Cheshire Cat too! Used to drive petrol accord, it was good car etc but I don't like characteristics of petrol engines. I get pain in my ears to hear engine scream. Unless if it was V8 but then if you drove diesel V8 that would be entirely different story. I would say one thing for sure, seeing fuel gauge going down so quick irritated me most. Now things went from 30mpg to 50mpg and that is encouraging to more adventures.

Petrols are for folk who like changing gear

I like changing gears in my diesel and that's coming from a SS 😉

Tinas - either you had a rubbish diesel or you have no idea about driving them. I've never driven a diesel that did that. In fact one reason I like driving them is that they are the opposite. Ease down the pedal and you go whooshing away regardless of gear.

Was it a 1.8 tdci? They are famously bad. Or was it an econetic one? The VW equivalent are mapped with a lack if torque at the very bottom end I think.

And as for V6 3.0 petrols, they are nice to drive, no arguments there, but they aren't cheap and would be doing well to get half the mpg I do. Not really a like for like comparison!

tinas - you were either doing it wrong or it was a very underpowered diesel that was never going to be quick.

fwiw I had the same experience sat in the passenger seat of my bro-in-laws 320i this weekend. He was driving everywhere with the rev too low so it was accelerating like he'd hitched up a tractor to the back. Had he been driving a 320d, progress would have been brisker. I think he is still in the mindset of driving their Polo tdi.

The whole run out of revs thing makes no sense, either. Generally diesel are geared longer to take advantage of the torque.

Decided dizzle is the way to go 🙂

90% set on a Mondeo ST TDCI (still) / 10% of me wants to go and have a play in a newer shape Mondeo Titanium X. Both can be had relatively cheap with low enough miles for me to not to have to worry about DMFs etc for another 4 or 5 years (doing our current mileage) and the petrol equivalents aren't that much, if any, cheaper (apart from the ST220 but I'm not getting a 3L V6).

The last time I drove a diesel like the one Tinas mentions the turbo pipe had come off, that is certainly nothing like the last few diesels I've owned. I still don't get this you have to drive them different thing, I drive them both the same but then I drive them like I was taught during Police driving training, we used the Police driving course when I did mine.

you dont HAVE to ...but it helps......

if you have a petrol with enough power (as most police cars will be) then its a non issue... my 3.5 v8 drives similarly to my 1.9 diesel...but has 165bhp and does 4-15mpg compared to the 80 bhp and 45mpg of the diesel....

trail_rat - Member

Petrols are for folk who like changing gear

How about petrol with automatic gear? I got one and enjoy it very much. It's a 2005 Toyota Corolla 1.6 auto and it's fast enough to hit 70mph. Fuel consumption is around I think 30mpg.

Manual gear is sssoooo yesterday ...

😆

if you have a petrol with enough power (as most police cars will be) then its a non issue.

Well I don't drive those but have you seen most Police cars?

I'm talking about my own cars, work vehicles which ranged form Renault Masters, Ford Transits although that was moons ago, Discovery, Focus and others. Drove them all the same as we were taught use the gear through right through the revs and often skip gears when going up. Both petrol and diesels were fine and drove pretty much the same.

I've haven't got any proper figures, but I recall a piece on Top Gear (before the buffoons took over) comparing used cars petrol v diesel.

Comparing the extra cost for a deisel model (same spec) and then the quoted, not real world, fuel usage. You'd need to do 50k miles before the costs equalled out. I think this was on a £5k petrol v the £6.5k deisel cars, same spec car.

My thinking is deisel: more to buy, more at the pump, although you visit less often, more to service, more wear on service parts (brakes, suspension, tyres), better towing, better on longer motorway trips.

Back then when Top Gear was about walking around a car mumbling; the price differences, servicing intervals and deprecation of diesels and petrols were a world of difference to now.

I love the MPG I get from my diesel and love the torquey feel.

12,000 miles, 48mpg, 0-60 7.1 sec, 185hp

That's 48 MPG mainly city driving in London and I rag it as much as possible - I usually get 55mpg-ish on long runs. Best I have done is London to Bournemouth with a 62mpg average over 100 miles.

2012 BMW 120d

Congratulations, you're 23,000 pound car has saved you 3-400 each year compared to a car that does 35mpg. The first years depreciation is over 4000 pounds btw.

(Sorry, I probably sound slightly bitter, but i just had to change a DMF and it wiped out over 2 years fuel savings.)

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise

Myth. How can it?

I wish mine did I would get my record of 92mpg then.

The thing is with mpg figures is that people believe their trip computers and only ever look at them now and again anyway.
I'm a fuel geek. I've been recording every tankful in most cars and bikes I've owned for 20 odd years. Solamana will confirm this as I gave him 50,000 miles with of records with the Vectra as mentioned earlier (44-45 average IIRC)
Now I do it all on a phone app. I can look at the graph it generates and tell you why the figure rose or dropped. I know, for instance, that fitting cruise control on the Focus costs me fuel. I'm more economical with my right foot than the electronics can manage.
That Vectra: take it easy 49mpg. Load it up with people, put 3 bikes on the roof and drive to Afan: 37mpg.
Work an engine harder and it uses more fuel. Fact.

^ I do the same PP. My OH thinks I am very sad. I agree with her, but I've done it for so long I can't bear not to...was averaging 54mpg until changing my driving style & slowing down to 60 on my commute. Now averaging 62+mpg. I wouldn't bother if I wasn't doing a 400 mile/week commute & I have to leave early to beat the traffic so driving at 70 just means I get to work even earlier.

I haven't experienced the whole 'diesel cost more to run' thing. Servicing is comparable to my last car; a 1.4 petrol Fiesta, tyres last ages, it's only on it's second set of front discs & pads (197k miles on it & the 1st set managed 119k miles), original clutch, original dmf, original turbo etc...anti-roll bar bushes need doing again, so they last about 100k miles.

Maybe i've just been lucky...

I've tested the car trip against my maths and found them to be so close it's not worth me worrying about doing the work myself.

Stumpy, yeah agreed! 🙂
Like I said, our diesel was fine too. It's just the big 'IF' it goes wrong I think!

I know, for instance, that fitting cruise control on the Focus costs me fuel. I'm more economical with my right foot than the electronics can manage

Hmm.. this is a debate that raged for a while on the Prius forums (yes you may hate the car but PP they are even worse fuel geeks than you!).

In my experience, if it's windy then cruise is worse, but if it's open ie motorway then cruise is better.

It's difficult to maintain exact speed on a motorway by hand (or foot), and slightly slowing down and slightly speeding up all the time reduces MPG - even if it's not enough to notice. If I ease down ever so slightly on the pedal, so gently that you can't even tell, the mpg readout goes down loads. More so in the Prius, but it still applies in the Passat.

I use cruise all the time when the road is open and not too windy/hilly.

In my experience, if it's windy then cruise is worse, but if it's open ie motorway then cruise is better.
It's difficult to maintain exact speed on a motorway by hand (or foot)

Now, see, that's the key. Steady speed. Lots of people can't keep a steady speed to save their lives and waste fuel as a result. (I think you can though Mol. I think you know what you're doing 🙂 ) so cruise saves them fuel.
But there's more to it than just a steady speed I think.
When I'm driving with my foot, I'll keep a steady throttle going downhill and speed up a bit. Maybe 5 mph or so. As I come to the rise the other side ill gradually slow down as I climb. So I might have chosen 65mph as my speed but increase it to 70 downhill and reduce to 60 on the way back up.

I think that's how I beat the cruise control: it uses more throttle to get up hills by keeping the speed constant.
It wasn't a big difference. 1mpg, maybe a bit more. But I definitely noticed it

Also, it's not OE cruise and its not that sensitive. That doesn't hell either.

Cruise on the mondeo is definately worse on uppy-downy roads, ime... Not it's fault, it can't predict the road ahead in the same way as a driver can, so it wants to power up the hills then immediately starts engine braking on the descents, rather than using the gradients.

On relatively simple roads it does seem better though. And certainly stops me from slowing into corners then deploying the lead boot on the exits.

Ah.. cruise does vary in accuracy yes. It's pretty good on both my cars, but on some autos I've hired in the US it's been poor.

It does save energy on resonable gradients as you say but I don't want to drive like that.. people varying their speed pisses me off! In certain situations without traffic beind me I have slowed up hills. The A30 I think over Dartmoor is so hilly that it's better not to use cruise. However 8 times out of 10 I am driving along the M4 which is looong gradients.

Another thing I do when there's not much traffic around is coast towards roundabouts etc. In the Prius it's possible to touch the throttle and roll without the engine turning at all, using electricity or even nothing at all depending on speed. On the A4042 with lots of roundabouts I gun it up to 60 then just roll to the next one.

Another thing I do when there's not much traffic around is coast towards roundabouts etc. In the Prius it's possible to touch the throttle and roll without the engine turning at all, using electricity or even nothing at all depending on speed. On the A4042 with lots of roundabouts I gun it up to 60 then just roll to the next one.

To be fair I'd like to drive a Prius to see what they're like.
What sort of MPG do you get? I'm assuming its free VED too?
But coasting, yeah, I reckon that's why I'm doing so well out of my auto Omega in part. It seem with an auto you can come off the throttle nearly 1/2 mile before a junction and it doesn't have the same engine braking and rolls on for aaaaages. I've said before on here that I think my style suits an auto. I like them. Always have done.

Just out of interest, what apps are people using to record fuel economy??

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise

Myth. How can it?

@daveyboywonder - I just keep the receipt, write the mileage on it & then use a simple Excel file. Probably a bit of a heathen way to do it, but it works, I don't always have my phone with me & I've been using this method since before you could buy a smart phone...perhaps i'll swap over at some point.

Filled up this morning - 64mpg for the last tank...

Edit:

TINAS - turbo lag...really? If you are thrashing a diesel I assume you'd be keeping the revs high enough and turbo lag is virtually non-existent. A lot of people confuse turbo lag with the gutless feel of a diesel below about 1700rpm. That's not turbo lag, it's just that below a certain revs the turbo isn't being utilised. People who confuse this with turbo lag, normally stick their foot to the floor when the engine is doing 1200rpm & complain that nothing happens because of turbo lag. But it isn't lag from the turbo, it's just that the engine is effectively running NA until such revs are reached that the turbo comes into play.

Just out of interest, what apps are people using to record fuel economy??

Road Trip. Works very well. I think there's a free version to try too.

my 3.5 v8 drives similarly to my 1.9 diesel...but has 165bhp and does 4-15mpg

wowsers - what engine has 3500ml of displacement, yet only eeks 165bhp from it??

Gotta love modern tech - 200bhp from a N/A 2L petrol is easily within reach!

DrP

I put it down to the turbo lag, the engine is gutless until it spools up

We've also done this before. Turbo lag all but disappears above a certain engine speed - about 1500rpm in my car. Below about 1200 rpm (where you shouldn't be driving much anyway) there's not enough exhaust gas flow to even turn the turbo effectively. A turbo is something you have to know how to work with if you want to drive a certain way - it's the same for petrol and diesel.

If I am driving normally and gently at low revs there's only half a second delay before I get all the power I need in any gear. I do not have to shift. However it is different in different engines, which is why I asked what model Mondeo you had.

well, assuming the ECU doesn't overfuel until the turbo spools up and starts delivering more air)

Some do, to varying extents. That's why you see a puff of brown smoke when they pull away sometimes. They are trying to get the turbo going as quickly as possible.

To be fair I'd like to drive a Prius to see what they're like.
What sort of MPG do you get? I'm assuming its free VED too?

Mine's a MkII so I'm band B £15/year. The new ones are A and much better cars to be honest. Faster, bigger, plusher and more economical.

As a car to drive I find it refreshingly easy. Light steering, the powertrain is always super smooth, you don't have to make any effort to drive smoothly.

They are quite sensitive to driving style, which is why some people report 45mpg and others get 60mpg easily. All the usual economy tricks like reading ahead etc seem to make more difference in the Prius.

When I was driving to Aldershot, between leaving the M4 and the Wellington Monument via Fleet I could only maintain average mpg in the Passat, but I could get it up by 3 mpg in the Prius.

wowsers - what engine has 3500ml of displacement, yet only eeks 165bhp from it??

I presume that's the old Rover V8 (as fitted slightly more recently to various Land Rovers). IIRC it only gave 150bhp in the standard SD1.

They are quite sensitive to driving style, which is why some people report 45mpg and others get 60mpg easily. All the usual economy tricks like reading ahead etc seem to make more difference in the Prius.

When you pull off or just drive slowly, do they just use the electric motor or does the electric just assist the petrol?

And what's the boot like? Could you put a bike in with the front wheel off, for instance? Or is it taken up by batteries?

[i]wowsers - what engine has 3500ml of displacement, yet only eeks 165bhp from it??

[/i]

Original Rover V8, ok in its day - Ford Granada's and the like only got 150bhp from their 3.0i and sub 20mpg.

But you could easily get away with a 3-speed gearbox 🙂

If you pull away normally, it's electric to start with then the engine kicks in depending on how much torque you've requested, and how much charge there is in the battery. If you are just creeping forward in traffic, or closing a gap in a traffic light queue or something, you'll stay electric. You can be in a long queue of several light cycles and use no petrol at all in 5 mins, which is quite nice. Then when you get back into a normal car you think 'shit why the hell is my engine still runnning, I'm wasting fuel here!'

If you lift off when driving at any speed the engine stops and doesn't even turn over.. it applies a bit of recharging to simulate the feel of an auto. At this point if you touch the pedal ever so slightly it'll just freewheel completely, engine off, no braking, and it'll roll for ages only losing a couple of mph. Great technique for saving fuel 🙂

The boot - on mine, it's deeper than say a Golf but shallower. Not dissimilar really. With the seats down however it's pretty big - as long as an estate although not as square. It'll take bikes in with front wheel off no problem. The boot floor is level with the rear sill. The batteries go underneath that, but only about 12" deep from the back of the rear seat. There's a storage compartment under the floor right behind the sill about 8" deep and 18" long. If that makes sense. The spare wheel is under that.

The new one is bigger - the boot is I think taller in the back, not sure if it's slightly longer or not. I say new, they've been out since 2009.

If you are just creeping forward in traffic, or closing a gap in a traffic light queue or something, you'll stay electric. You can be in a long queue of several light cycles and use no petrol at all in 5 mins...

I want this retrofittable to all cars!

DrP

Toyota are giving it a good go, and Ford in the US.

I drove our petrol and diesel yesterday. The petrol will do 7500rpm (2.4L) and is smooth to drive, plus great to drive on local roads. The diesel I use on the motorway and it sits at 1800rpm at ~80pmh, super comfy. Petrol and diesel - pro and cons for each.

'My OH thinks I am very sad.'

Funny that! Still you're in good company on this thread! 😉