Petrol or diesel - fuel economy

[str]

Currently swapping my diesel with the wife for her 1.25l petrol fiesta!

Currently commute approx. 100 miles a day, about 20,000 miles a year and had been thinking of looking for a diesel focus or astra, 1.6l engine, maybe 5 years or so old, but quite pricey.

What with petrol cheaper at the pump and petrol cars cheaper to pick up, is it worthwhile considering a petrol car? Or is it a false economy?

Any suggestions welcome!

 

[freddiemercurystwin]

Only way is it do the math, then you'll know.

 

[foxhole]

http://www.parkers.co.uk/cars/petrol-vs-diesel/
You still have to consider other factors like performance, what price you put on reliability and how long you keep a car for.

 

[Peter.N.]

It depends a lot on your driving style, a diesel will reward you far more for driving it gently, if you drive flat out all the time not a lot to be gained. Another factor is the way you want it to drive, most diesels are far more relaxing in that the big low down torque means you don't have to change gear at lot, many diesels will pull right down to tickover. My 2.0 Hdi 406 will quite easily do 60+ mpg on the motorway at around 60 mph and averages nearly 50 mpg, even my old Citroen XM with a 2.1 td IDI engine will do 55 mpg if driven with a bit of restraint. I prefer the lazy driving style of a diesel - but then I'm old

Peter

 

[Burnerman]

I've been fully diesel since 1986, from the old indirect injection clunkers up to the incredible variable vane / nozzle turbo ones of today. For me, there simply is no choice.
However, small engine petrol cars, driven lightly can achieve superb MPG too.
John

 

[ajrobb]

Fuel is sold by volume but the energy is more to do with mass. Diesel is about 13% more dense than petrol so you have to knock 13% of the price of diesel before making the comparison, so diesel is much cheaper than petrol. Then diesel engines have a higher compression ratio and no throttle, both of which make them more efficient than petrol. At idle, a diesel engine is much more efficient than petrol.

That said, I drive a petrol Toyota Prius hybrid as I was commuting 140 miles a day. I regularly got over 60mpg. For short journeys around town this can drop to 45mpg. The CVT automatic transmission does good job of improving economy and is a relaxing drive.

 

[Whitworth]

Went diesel about 3 years ago. (Fiesta 1.6TDCi) Love it. Good in stop start traffic (no revs just lift the clutch) Not far behind the 1.6 petrol on performance. 58mpg on 40 mile round trip A and B road daily commute.
Good in the snow as well again due to not having to use the throttle to move off. No ignition system coilpacks etc, damp proof
Probably right about taking a lot of miles to pay the extra for a diesel engine but if your buying second hand this won't be such a factor.
I wonder if the petrol stations will ever make a diesel pump that doesn't seem to leak all over your hands though

 

[alfajon]

You could always go for an LPG conversion. I have an Alfa 156 V6 that I am just replacing the clutch after 60K. The car is worth between £700 and £1500, but I love the performance, hate the economy. Dare I say it I am thinking of going gas. I have had the 156 for 5 years and put 20K on the clock since I have a VFR800VTEC motorbike to commute 20 miles each way. However once a month I do 600 miles in a hire car for work. I could use my own, but its not economically viable in the Alfa, unless I turn to Gas. I could Px for a diesel so Gas conversion £1400, tops I'm looking at £2500 - £3000, lots of choice, but with 190BHP, 60K and a new clutch and a big when you drive. The running costs would be the same for a diesel, but I would not have the major depreciation (unless you include the lost money for the conversion).

Just a thought since LPG is circ 77p compared with £1.36 and £1.42 for petrol / diesel respectively. Don't forget Vauxhall and Volvo offered LPG on some models new that have a cheap road tax.

Jon