Quote:
Originally Posted by capt jack
You need to do the sums, not rely on the on-board computer! If over say a 1000 mile period of your usual driving style your car does 32mpg, then with petrol at £1.20 per litre - that's £5.46 per gallon, your fuel cost is 17p per mile. That same car, driven the same way, will do at worst 26 mpg on LPG. If LPG costs 70p per litre, £3.18 per gallon, then your fuel costs are going to be 12 per mile, that's a saving of 5p per mile. That's equivalent to £1,000 saved in 20,000 miles. If the cost of conversion is £2,000 then it'll take you 40,000 miles just to get your money back.
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The fuel consumption spread can be rather bigger than that in my experience. The best I've ever had out of my 940 turbo on LPG is 22mpg, on petrol best ever is 36mpg.
It consistently does 19.1mpg on gas; 46 litres every 200 miles, and that has stayed within a few percentage points over 150k miles. Normally it'll do 28-29mpg on the same usage on petrol. Part of the issue seems to be that it is a turbo.
Don't get me wrong, I like LPG and don't regret converting the car at all and it has been a very worthwhile exercise. But there can be a significant fuel economy penalty. Rather more than the 5% a lot of the conversion websites quote.