[SyncroS8]

I did some fairly accurate calculations on LPG now with the price of £1.359 for petrol and £0.76 for LPG.

I'm basing my figures on the car getting 20% less MPG on LPG than Petrol and a figure of 25mpg (not that easy to get with a 4.2 Quattro V8 Petrol).

£1.359 = £6.178014 per Gallon for Petrol
£0.76 = £3.45496 per Gallon for LPG

1,000 miles on Petrol @ 25mpg will cost you £247.12056.

1,000 miles on LPG @ 20mpg (20% less than on petrol) will cost you £172.748

These figures are easy to multiply up and down so if you're doing 20,000 miles a year, just multiply by 20 etc.

Taking the figures above, on petrol you're paying 24.7p per mile. On LPG, you're paying 17.3p per mile.

For comparison purposes, 17.3p per mile is the equivalent of approx 36mpg so you're not matching the TDi figures.

Diesel does cost around 6-7p more per litre, but just for the record...

Diesel here costs £1.429, £6.496234 per Gallon.

1,000 miles on Diesel @ 45mpg will cost you £144.361, or 13.3p per mile.

The question is can you really get 45mpg from the 3.0TDi in an A8? I know about the figure of 25mpg from my own 4.2 S8. Maybe you can get a realistic 30mpg on an A8 with the higher gearing?

I hope that this helps your choice about vehicles.

MG