Hey, gang! Now that I've owned my 1974 Series 3 Roadster for a month, I've noticed that she doesn't exactly sip the petrol. I appear to be only getting about 11 miles per gallon. At least, I went ~55 miles on a quarter tank of gas, so unless my math skills are poor that's ~11 mpg. I don't floor the accelerator, I don't really go over 65-70 on the highway, and I don't often sit in traffic. What can I do or look at to try and improve my mpg?

Thank you

 

For an American gallon, this looks a bit low, but remember this is a 5.3 litre V12 with carburettors. The V12 XJ, admittedly a lot heavier was around 11-12 mpg on a British gallon. I'm afraid that we have unfortunately got used to mpg figures for digital fuel injection, so can be shocked how poor fuel mileages were back in the day. My MG Midget 1500 was pushed to achieve 32 mpg and that is a very small car with an engine just over 1/4 the size of your Jaguar engine.
Does your car still have all the emissions junk installed for the US market ? That had a serious deleterious effect on economy.

Edit
And of course, being an automatic is not good for fuel economy either.

 

All the above spot on. Also, another important point - you only did 55 miles.
With carbs, while a car is warming up, fuel consumption is very poor. It then improves as the engine gets really warm. With your car, that could be at least 10 miles; so about a fifth of your journey was done on poor consumption, affecting your overall figure. If you filled up after 55 miles, then immediately did another 55, you'd see better figures.
I would have thought that with a well tuned engine, on a LONG run, you could get about 14 mpg (British gallons)

 

I’ve had my 1973 E-Type for several years and the carburetors are well balanced. Because most of my enjoyment driving is around 20 miles or less, I’ve calculated a round number of 10 mpg unless I take it on the highway.

Best driving experience and well worth the low fuel economy. I totally agree that these automobiles run much better when warm, which doesn’t take long with a V12.

 

I really appreciate all your insight. Thanks a ton! I'm taking my car in this week to get a new power steering pump installed, so I'll inquire about the emissions stuff while I'm there