I have a 95 XJS V-12. I get approx 15 to 17 mpg. I have seen several post where the gas mileage was averaging 18 to 22 mpg with a V-12 or a 6 cyl. Are these post for real or do I have a problem with my engine. Everything seems to be fine but I cannot get these kind of mpg. I also have a 96 XJ6 but it does not average but 15 to 17 mpg. One of the reasons I purchased the V-12 was the mpg people said they were getting. I still love the car with its 15 mpg, just have to fill up more often.

Submitted by SE21-33540J on Tue, 09/01/2009 - 16:17

David,

I think some of the gas mileage claims on V12 cars may be coming from Canada where they use the Imperial gallon. That would give a mpg of 20% higher than we get with a US gallon. My understanding is one imperial gallon is approximately equal to 1.201 U.S. gallons. One imperial gallon is exactly 4.54609 litres, whereas one U.S. gallon is exactly 3.7854118 liters. It could be the explaination, or it could be one of the things Robert referred to.
You also might look into using a K&N air filter on each side. I did this on a Daimler Double Six I once owned and went from 18 highway to 20 highway. However there is no cure for a heavy foot.

Submitted by NC19-03320J on Tue, 09/01/2009 - 14:53

David, I was told many years ago by an old man that the three things men lie about the most is, how fast their car will go, their gas mileage and their sex life!