What car?

[Ultrasonic]

Originally Posted by cepheus

Read more: http://www.thisismoney.co.uk/money/c...#ixzz1w3dtJfSk

Interesting link. One thing perhaps worth highlighting is that the above 10,000 mile threshold is based on the following (quoted from link):

It bases them on owning a vehicle for a typical three-year period and uses the price of a three-year-old vehicles for its used car model.

Whether it would hold for the older diesels that the OP was asking about I'm not sure. That said, the idea of there being a mileage threshold above which it becomes more economical to drive a diesel is hardly a new one, and I'm sure I remember a roughly 10,000 miles p.a. threshold being talked about years ago.

[DUTR]

Originally Posted by Ultrasonic

But those economy figures a crap compared to a decent diesel. I've got more than 60 mpg on long runs, and have averaged 55 mpg on all driving over the whole of the last year (including a 9 mile each way daily commute with lots of roundabouts to be slowed down for).

Driving style obviously has a big impact on fuel economy. It may be that if you buy a diesel to drive aggressively then you may as well buy a petrol (I don't know), but for people who buy a diesel for better fuel economy and drive accordingly I still would have thought they'd be better doing this than buying a petrol.

You missed out the essential part though, the laws of physics rule, two vehicles of similar power output but of different fuel types eg petrol and diesel with the same driving style will return similar MPG.
The figures I posted were round town, on a run from Birmingham to Preston at legal speeds my Golf returned 39mpg where as my friend on the same run with a diesel edition returned 42mpg, considering he was paying more for the diesel/litre me thinks the GTI required less ££s for the round trip.
I'm not suggesting deisel is rubbish and petrol is good, each variant will suit the owner's requirement.

Forgot to add, if typically deisel owners are returng often 60mpg , why are they complaining about fuel prices, as it would take a good amount of price change before any significant in miles/£ is noticed, eg £10/1.38 litre returns 95 miles for the tenner, if fuel suddenly jumped to £1.45/L then the driver would still get 91 miles for the tenner, next to no difference really

[cepheus]

Originally Posted by DUTR

You missed out the essential part though, the laws of physics rule, two vehicles of similar power output but of different fuel types eg petrol and diesel with the same driving style will return similar MPG.
The figures I posted were round town, on a run from Birmingham to Preston at legal speeds my Golf returned 39mpg where as my friend on the same run with a diesel edition returned 42mpg, considering he was paying more for the diesel/litre me thinks the GTI required less ££s for the round trip.
I'm not suggesting deisel is rubbish and petrol is good, each variant will suit the owner's requirement.

Sorry but you don't know much about the laws of physics!

There are many factors involved here, but the main one is that Diesels work at a higher compression ratio, which means more energy is extracted from the fuel (for conversion into mechanical work) during expansion of the gases.

Another important factor is that energy isn't being wasted throttling the air during intake with a Diesel.

The former is particularily important on Motorways, the latter during town driving.

[mikey72]

Originally Posted by cepheus

The fuel consumption difference isn't that great. Figures are usually exaggerated but both to a similar extent............

Diesel £6.31 a gallon, our C3 does 60 to 70mpg, so about 10p a mile to move. Petrol £6.04 a gallon, our Zafira, does 25 to 35mpg, so on average costs about 20p a mile to move. 10p a mile difference in the two. So that's £500 more ayear for 5000 miles, £1500 a year more for the 15000 we do in the C3, or a grand total of £2500 a year more for the op.

[worried jim]

Originally Posted by DUTR

I will believe diesel is as good as petrol when I see diesel cars next to petrol in motor sports

Please refer to post 8.

[DUTR]

Originally Posted by worried jim

Please refer to post 8.

I did see the picture in post #8, is that car featuring in the Monaco GP this afternoon?

[getmore4less]

Originally Posted by DUTR

You missed out the essential part though, the laws of physics rule, two vehicles of similar power output but of different fuel types eg petrol and diesel with the same driving style will return similar MPG.

Diesel contains more energy than Petrol

By your reasoning a gallon of wood would give the same MPG

[cepheus]

Originally Posted by getmore4less

Diesel contains more energy than Petrol

By your reasoning a gallon of wood would give the same MPG

Yeah for that reason as well.

PS the wood might be even more smoky! It can be done though



Wood gasifier on a Ford truck converted to a tractor

[Ultrasonic]

Originally Posted by DUTR

I did see the picture in post #8, is that car featuring in the Monaco GP this afternoon?

I'm pretty sure the R10 would break one or two of the FIA regulations .

[DUTR]

Originally Posted by getmore4less

Diesel contains more energy than Petrol

By your reasoning a gallon of wood would give the same MPG

Not sure what you are saying there, what I meant in the post and as others have pointed out, if you drive a deisel hard, it will be as poor economy as petrol, if you drive a petrol frugally , it will be near as economical as a deisel, what others are pointing out is there is little difference in running costs between the two for all but highest annual milages.
eg I fill up every two weeks , swapping a 2 litre GTI for a half the power A3 1.4 diesel would save me 4.4 gallons a month for the same journeys, however the extra £5ish a week fuel premium for the use of twice the BHP and ability to overtake a tractor or bus is justified for me, I couldn't do much with the £20 per month or even £240 per year

[Ultrasonic]

<This is pedantic but I feel professionally obliged given the posts above - feel free to completely ignore!>

Originally Posted by getmore4less

Diesel contains more energy than Petrol

The energy density of Diesel is higher than petrol if given in units of energy per unit volume, whereas energy density could equally well be given in units of energy per unit mass in which case that of petrol is higher. The former is the one of relevance to fuel economy measured in mpg though. See here:

http://en.wikipedia.org/wiki/Energy_density

p.s. I am a physicist. The detailed operation of Diesel engines is however a matter of engineering, where I defer to cepheus' excellent earlier post.

[mikey72]

Originally Posted by Ultrasonic

<This is pedantic but I feel professionally obliged given the posts above - feel free to completely ignore!>



The energy density of Diesel is higher than petrol if given in units of energy per unit volume, whereas energy density could equally well be given in units of energy per unit mass in which case that of petrol is higher. The former is the one of relevance to fuel economy measured in mpg though. See here:

http://en.wikipedia.org/wiki/Energy_density

p.s. I am a physicist. The detailed operation of Diesel engines is however a matter of engineering, where I defer to cepheus' excellent earlier post.

Hmmm, I now have a mental image of Sheldon of The Big Band Theory

[Joe Horner]

Originally Posted by Ultrasonic

I'm pretty sure the R10 would break one or two of the FIA regulations .

It would also be considerably more practical as a daily driver than anything in the Monaco GP.

Seeing as most of us tend to drive on the road, that makes the diesel one the "better" car

[worried jim]

Originally Posted by DUTR

I did see the picture in post #8, is that car featuring in the Monaco GP this afternoon?

No, but most of the cars this afternoon are hybrids in some form due to their KERS systems.

[Ultrasonic]

Originally Posted by mikey72

Hmmm, I now have a mental image of Sheldon of The Big Band Theory

Much as I hate to admit this, that mental image isn't as wide of the mark as I'd wish! I would like to think there are one or two differences in our personalities though . Like the fact I'm not about to suggest that you meant 'The Big Bang Theory'. Oh crap, I just did .

[cepheus]

An interesting article. If everything in life was unreliable as a Volkswagen we would be in deep $h!t

Many motorists will face an annual repair bill of over £797 in the fourth year of a car's life, from top faults like gear boxes, sensors, electrical faults and clutches which are most likely to fail, according to Used Car Expert.

Its research found that the five models over three years old with the most faults are the Honda Jazz (2008-), Citroen C5 (2008-), Audi A4 (2008-), Chrysler Grand Voyager (2008-) and the Vauxhall Insignia (2008-).

Read more: http://www.thisismoney.co.uk/money/c...#ixzz1wFa6LLQl

and which manufacturer has a 5yr warranty as standard? This was useful for fixing my Hyundai's air conditioning just before the warranty run out which would have cost me a fair bit!

http://www.petrolprices.com/manufact...arranties.html

[Mr Thrifty]

Diesels are so slow and smelly, just like buses and trains

Fast motorbikes use petrol and so do formula 1 cars