Facelift AJ16 Reporting Low Fuel Economy

(Veekay) #1

I have a 1996 XJS, AJ16 engine, about 113k miles.

I do a mix of city and highway driving. I seem to be averaging 15mpg. While I don’t drive conservatively, I’m also not hammering down the gas pedal at each green light either.

My LTFT is zero. Both banks.

The only unusual reading I’ve picked up is that my coolant never goes about 180. With the heat on its at 176F and without heat, it’s at 179.6F.

Would a stuck open thermostat cause that kind of fuel economy?

(BobboSD) #2

Yes I think so. My 1996 XJ6 had a thermostat stuck wide open and exhibited terrible gas mileage until I replaced it.


(Robin O'Connor) #3

Agreed that would cause bad fuel economy, should be above the 20mpg range, thats what I was getting from my AJ6 in the ‘40 and I didn’t pussy foot around.

(Veekay) #4

Excellent. I have a thermostat set at 88C on it’s way! That’s going to be about a 10 degree difference, and more importantly warm up the engine faster I imagine.