My '04 has 109000 miles on it. Drove 344 miles, mostly highway, but there were in-city stop & go areas. I also have an 02 sensor that needs replaced.


Still averaged 26.2 mpg. I thought that was pretty good.

 

Combined driving that isn't that bad. Last trip I took which was about 1k all highway I got about 32mpg.

 

It seems that most of the reported mileage in the 27-37 range are from NA engines. Would be intrested in the results from SC engines. I seem to get about 23-25 from my SV8 at highway travels 70-75 mph. Am I getting crappy mileage, or just have a thirstier engine on the highway? This is reported from the trip monitor reset at highway speed. I know that the trip monitor isn't the most accurate (too many varibles)
Maybe its time for new plugs, and vacuum leak check.
Yes, I run premium fuel.
And ofcoarse I can empty a tank in-town with a stomp to the floor, resulting in super sonic launch. Oh that sad little red corvette in my rearview mirror!

 

For a car of its size, the x350/x358 have great highway gas mileage. If I cruise at 70-75 I can get 32-33 mpg. Cruising at 80 and I still get 27-28mpg.

 

But yet again, a NA engine.

 

I lost 15% mileage when they forced the ethanol into my tank. Hope that stuff burns cleaner for the environment, because otherwise it seems no better than adding water to the gas!

 

Maybe those with SC engines don't want to fess up.

 

Mine is a SC engine.

 

My STR (same engine etc) also gets a bit less MPG than the NA V8. Off boost it's lower compression and there's the SC still there.

I measure MPG out of curiosity and in case it suddenly gets worse but that's about it.

(I'm quite impressed with the MPG, even so.)

 

I shouldn't complain about my mileage. Document printed mileage from EPA and MFR for 4.2 S/C is 15/22-18 combined. I'm getting better than that. The good thing is that it's the same for short and long wheelbase.
So thats the end of that story. I'm still going hunting for vac leaks!
I do have to remember that mileage in NO way is a factor in purchasing such a great car. I'f you cant afford the gas, you can't afford the car. I dont think that any of us even thought for a second about mileage when we saw these cars for the first time. "Mileage, who cares, just look at it."
I just have to smile when on the way to supersonic, and just think of the fuel blowing out the pipe! Really, the last thing on my mind when she spools up is fuel mileage.
I think the usefull part of compairing mileage between us, is to possible identify a possible fault.
Thanks for all your input.

 

I see where Mitsubishi got dinged for cheating on MPG claims. Jaguar, on the other hand, seems to be a bit conservative on their claims. The last two Jaguars I've owned, a 2005 S-Type and my current 2006 XJ8L have exceeded the highway claims. The in-town figures I get are probably a bit low because the DC area traffic is so bad, so I'm not considering that figure. What's funny is that the Jaguars beat a number of econoboxes but offer none of the comfort or performance attained by the two Jaguars I've owned.

 

I have consistently gotten 28 mpg at 70mph on my road trips.
04 XJR S/C

 

Have to agree, everyone asks me about the fuel and I say "Look at the car, worth every drop!".

I try to use the sport button sparingly but when my girlfriend asked me what it was I said "Smile and get ready to refill"

 

That made me really laugh out loud. I'll use that next time.
Thanks

 

Having put about 1500 miles on my "new" '07 XJR, seems I get ~ 22-23 mpg best case on highway

Is there a problem with my car? I'm astounded by 27mpg XJR noted above

BTW,my Audi A8 was consistently 26 - 28 mpg highway; NA ~300HP 4.2L and AL body as well

My M5 was ~21 - 22 mpg; NA ~ 400HP 4.9L V8 6 speed

My M3 is ~22 - 23 mpg; NA ~340 HP 3.2L I6 6 speed (turns 3000 RPM at 70 mph)

My SVX Westfalia is ~17 mpg; NA ~230 HP H6; 4 speed (lousy aero and heavy)

 

Do you have the car in Sport mode or regular? Type/brand of fuel used? Tire pressures? Any check engine lights?

 

When I replace my 02 sensor, mine should fall in-line with yours.

 

I posted this back in Oct 2014

"On an 800 mile drive from MD to ME I averaged just under 27mpg in my 2005 XJR. On the way back only 24 mpg I believe because I used 93 Octane from Sunoco for 1/2 the trip. I notice that 93 octane gas seems to differ quite a bit from station to station.

From my local grocery store I only average 14 mpg locally but using Shell V Power it jumps to 22 mpg local driving. So now I am very careful where I buy my "petrol".

I will be interested to see what I get when I have reinstalled my rebuilt supercharger.

 

The XJR (S/C) V8 is pushing 400HP, not a great comparison to the Audi.
But your mileage sounds very similar to mine.

Also, will fresh O2 sensors really boost mileage that much?

 

I do have CEL (PO420: RHS cat efficiency). I will change one or both of the cats. I also have a set of plugs (NGK Iridium) waiting to go in. New coolant also awaits. I installed a new coolant tank and engine filters/oil already.

Is there anything else that typically needs attention at 90K miles? The engine seems to run great; plenty of power and smooth. No leaks.

I'm thinking of EGR valve, intercooler, MAF, TPS, O2 sensors, thermostat, hoses, belts, water pump, idlers, coil packs, chain tensioners, VVT seals, alt bearings, oil coolers, hydraulic lines? Things that go bad or get lazy at 9yrs/90k miles?

I've had to replace all of the above (and more) over the years on various German cars

I will be soon taking the car off the road to redo suspension bushes and service the trans. So, would like to do any engine stuff at the same go

Thanks