I'm just reading a review of the latest 1.4 litre diesel VW Polo (which is getting to be the size of the Golf now). The VW figures are around 61mpg but the test gave 58mpg on average!
With this kind of efficiency why on earth is anyone buying a petrol car now?
It seems like the petrol engine is slowly disappearing from mainstream cars now that fuel price is an issue. Alongside the old disadvantages of the diesel engine are going--i.e. heavy, noisy, sooty, slow
Is there anything positive to be said for the petrol engine?
It would be a lot more refined and faster in the car you're looking at. No nasty agricultural noise or vibrations at low speed. Diesel engines are still heavy - that's why diesel cars need stiffer springs on the front. Diesel cars still blow black bits from the exhaust.
When was the last time you actually saw a diesel car!
I suspect that more R&D is going into diesels. Range Rover's latest V6 diesel has the same economy as the previous engine but 54% more power (according to the manufacturer).
Yes. They don't rely on expensive turbos/uber-high pressure fuel pumps etc etc to generate decent power, and hence have a lot less to go wrong. For extra-urban driving (as in on the open road) there's often a lot less difference between the fuel economy of similarly powered petrol and diesel versions of the same car. The biggest economy advantage with diesels is for short journeys, and stop-start driving. Diesel cars are also more expensive to buy, and whilst they hold their value better, it's still ultimately more money to shell out, so for lower mileage use petrols still work out better value. Obviously this argument doesn't hold water nearly as much for older cars, but there's still a lot less risk of expensive stuff going wrong on a petrol compared to a turbo-diesel. And then there's the driveability thing - petrols have, and always will have a nicer throttle response and wider power band than diesels. That's courtesy of the good old laws of physics.
But diesel cars, if you know what you're buying and get the right model (early VAG TDIs are a cracking buy, and pretty resilient) are a very worthwhile proposition, but it's worth remembering that modern petrol engines are improving all the time in terms of fuel economy.
In news: snipped-for-privacy@bt.com, The Blue Frog wittered on forthwith;
Because MPG isn't everything.
I've owned over 120 cars, and driven literally thousands, but I've only ever owned two diesels. A Peugeot 405 which I was given and kept for a week, and a Turbo diesel Xantia which I've just sold.
Yes, it's less vibratory, has a much less peaky torque curve, a wider useable range, doesn't need to be turbocharged to be acceptable, uses cheaper fuel, needs less servicing, doesn't throw carcinogenic smoke everywhere, sounds better, is much more responsive, is more relaxing to drive, and lighter than the equivalent diesel so the car tends to handle better with a petrol engine.
A big petrol engine on LPG is damn near as cheap to fuel as a diesel and much nicer to drive. That's why most of the Range Rovers I've owned have been V8s with LPG conversions.
I'm driving a Merc 190E petrol auto now which I replaced the Xantia TD with as my daily driver. It costs around £15 a week more to fuel than the Xantia but I arrive at my destinations relaxed and at peace with the world. When I drive a diesel in town I get to my destinations slightly agitated because I've either been changing gear constantly or waiting for the turbo to spool up... and this is driving along at sensible speeds, not driving like a nutter, 40 mph dual carriageway mimbling but in City traffic. In the Merc, or any decent petrol, there's no hassle. Even my ancient VW Scirocco is more laid back than virtually any diesel I've driven - the exception being the Merc E280 CDi my brother owns, and that needs a 7 speed auto box just to be bearable.
That's the most sensible thing I've read in this thread. You do have to drive a diesel differently. I'd disagree with the other poster that said turbo-diesels are peaky- the band is narrower than a goot, large capacity petrol, but useful torque is there for much more of the time than a typical small petrol engine. The argument only favours a petrol engine if it's bigish, and a good one- say a VAG 1.8T, and as for the petrol being faster in a Polo- well, yes, maybe 0-60, but in typical driving the TDi will cane the 1.4 petrol. We've had a 1.4TDI 75BHP Polo, and a 100BHP 16V Petrol Lupo, and the difference in normal driving really wasn't what you might expect. The Lupo revs much better, as you'd expect, but the TDI pulled a lot better. The often-stated thing of having to change gear a lot in the diesel because of the narrow torque didn't apply either: I find that the petrol needs more gearchanges to make good progress to keep the revs up- in fact, I find that every time I drive a small-capacity petrol car.
DervMan has said in here that the 75BHP Polo is a bit flat at revs, (and I'm prepared to believe him). The TDi won't rev either, but it will pull a lot better in the low and midrange. Basically, people that hate diesels hate diesels. Personally, I much prefer them.
I much prefer diesels to petrol in the last three diesels I've had they all cruise at 70 doing just over 2000 revs in comparrison to the petrol hire cars I've used which seem to be quieter at tickover but noisier at 70 because of the higher revs!
In news: snipped-for-privacy@bt.com, Rob graham wittered on forthwith;
Diesels have a flat torque curve for around 2000 rpm, i.e 1800 - 3800 rpm but there's nothing either side of it. A decent petrol engine will have a lower torque curve but spread over a much larger range, i.e 1200 - 5500.
funny my 1.4l petrol does 60mpg, ( 60mpg for a 1.4 diesel sounds quite low ) and is rated to do that, and since diesel contain about 15% more energy than petrol per unit volume, that would make this VW about 15% less efficient.
but #1, diesels have a narrower range of mpg, so in town they significantly out perform petrol.
but #2, diesels can last a lot longer, in a standard car they will still probably be in fine working order, as the car they were in is crushed for scrap.
but #3, petrol engined cars are a lot lighter and so require a lot less energy to make.
but #4, petrol has been hit harder by regulation. its easier to pick on an individual than the diesel driving lorry companies. this will change.
but #5, what really is the issue is supply and demand, if every one had a diesel, its price would rocket and the price of petrol crash, so the ratio of the number of petrol to diesel engines is basically being maintained by the ratio of the various hydrocarbons being pumped.
so, at the end of the day diesel engines are more efficient and last longer, petrol are lighter and cheaper to make, so small fast cars have petrol engines, large load luggers have diesel, this makes sense, anything else is more a fashion statement than a technical decision.
How does a 70-ish extra-urban mpg turbo diesel Clio or Fiesta TDCI, or a
177BHP Audi A6 turbodiesel capable of a combined 39mpg and a 0-60 time of 8 seconds and top speed of 139mph sit with your theory that "small fast cars have petrol engines, large load luggers have diesel"?
Absolute piffle! :-)
Personally I prefer diesels because I can accelerate briskly and still return great mpg. The turbo lag is a minus point, but it's easy to live with IMO and you learn to work with it. I am stuck with a 1.6 petrol Focus right now and while it's not bad, I can't wait to get another turbodiesel. Once I got used to the fact they don't rev like petrols, I was hooked. It's a different driving experience, but I like it. Nothing to do with fashion statements. Each to their own of course, but it's unfair to make spurious claims about people's motivations in choosing petrol or diesel!
I also find that even small engined turbodiesels hold their speed better than equivalent petrols on hills, I don't have to change down to fourth on steepish motorway inclines, they just keep going. Even my little Fiesta 1.4 TDCI took hills in its stride in top gear and made motorway driving relaxing. Contrary to what some people feel, I find turbodiesels more relaxing to drive than equivalent petrols due to their high torque output.
This isn't going to be a like for like comparison. Perhaps you're looking at an instaneous 60 mpg figure on the trip computer? Or perhaps you're quoting the Extra Urban figure for the few 1.4 petrol cars that have 60 mpg or higher for this statistic (the only ones I know of are the Audi A2, the Civic IMA but I have a sneaky suspicion that a Corsa crept up into this bit too).
It's like me saying, yeah, I return low 50s from my Saab 9-3 diesel, but Johnny Chump here only returns low forties from his same year, same specification, same car...
All things being equal.
No. In percentage terms there's nothing in it, in practice you'll find the diesel has a much wider range of consumption figures. Drive a diesel hard and use all the power and high engine revs and it'll suck diesel and blow soot out the back very quickly indeed. Moderate your pedal use and speed and it'll sip diesel like an aged lady sipping tea.
Perhaps. This is unproven.
A lot less? No. The weight difference isn't as significant these days for two reasons. One, the host car is heavier to begin with, two diesel engines are getting lighter. A weight penalty of a generoud 80 kg (1.8 diesel versus 1.0 petrol, ish) on a 800 kg 1990 Fiesta is material, but add 200 kg to the base weight of the vehicle and it becomes less significant. Modern safety requirements have upped the kerbweight of everything...
What makes you think that?
Not really.
Hahahahahaha.
Skoda Fabia vRS is about the best example of a modern turbodiesel warm hatch.
Go further back in history and you'll find various Peugeot DTurbos and Citroen Volcanes.
"Pete M" wrote in message news:ej2g9c$l6$ snipped-for-privacy@registered.motzarella.org...
Absolutely... except in practice the gearing helps resolve this, because whilst the diesel's engine speed range is narrower, with taller gearing the speed range is comparable.
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