I do have a heavy foot when taking off from a light and I do like to drive as fast as possible (70mph to 74mph). My son drives the car also and he has a heavy foot starting and braking, So you are probably correct. I use 91 octane, in the owners manual it says to use 95 octane ROM, but there are no sellers of 95 octane around here.

 

I have yet to see 95 octane.. Unless you want to run race gas which is 100/110 octane..

I always run 93 octane from "known" chain gas stations(Hess, Sunoco, Mobil, etc). I never put no name gas in my X...

Maybe you got a tank of bag gas and the poor mileage is the result. Put in a fuel system cleaner and see if it helps.

 

Just to clarify - the 93 premium sold in USA is equivalent to 97 RON fuel spec'ed for Europe. Ours is 93 AKI(anti-knock index) which is average of RON and MON.

 

I always use Sunoco gas in my cars and have done so for decades, I did put a bottle of Lucas fuel system cleaner in.

 

I previously owned 2 X Types and discovered that, if overfilled with oil, their fuel economy went down dramatically. The local dealer pulled this trick on me 3 times between the 2 cars. Check and see if your oil level is over the full mark on the dipstick. If it is, you can use a Mightyvac unit to suck the excess out through the dipstick tube.

Regards:
Oldengineer
06 S Type VDP
10 Honda CRV
48 Chevy Fleetmaster Town Sedan

 

^ good point. I've noticed the same and I've heard other members report it also.

 

I get about 26 average. I always user the best gas posible. Sunoco 93 and every six months, I get the full injetors cleaned

 

I check the oil once a week, I was told to do this by the parts manager of the Jaguar dealership. I check it when the engine is cold on a level surface. The oil level is actually a tad below the fuel mark. I am down to 1/2 tank and the trip meter shows I've traveled 83.5 miles.

 

Do U take the car to a garage and have the fuel injectors cleaned thru the fuel rail? Every 6 months sounds like a bit much. If you are using Sunoco 93, (I use Sunoco 91), I think the detergents in this gas will keep the injectors clean for a quite a few years. Unless you are doing a lot of stop and go city driving, or driving dirt roads, then every two years would be OK. One thing I will say you are taking care of your fuel system. I have been told that fuel injector problems usually start when the fuel filter is not changed regularly? How often do you change the filter?

 

Yes. I take it to the garage to get it done. I do a lot of city driving. My family mechanic doesn't charge much for it. I really baby my cat!

 

Filled up yesterday. Trip odo was at 396 miles, and tank took 13.8 gallons. For those who're math challenged, that's about 28.7 MPG which is consistent with the 25-29 average I've been seeing.

BTW, I drive in a mostly gentle manner, and it's mostly mixed driving.

Since I drive in a non-spirited way where spark knock is virtually non-existent, I may try 87 octane. Then again, maybe not.

 

I'm not so sure about using 87 octane in your car. Car companies have reasons they write in the owners manual to use a certain octane gas. A lot of people will argue the computer will adjust to the lower octane, which is might, but that aside, what is the reason for the 95 ROM octane Jaguar suggests? Over the long term 87 might damage the engine or it might not. Personally I'd will use what Jaguar says to use. One other point I read an Q&A in Road and Track I think, the person wrote that his car required 91 but he changed to 87 and now he got lower gas mileage. The answer was kind of generic, saying that you should follow manufacturers guideline on fuel.

 

God Bless U.