2000
XKR Coupe
4 Ltr.
So far urban driving.
US gallons
driving style mixed, mostly sedate.
Avg MPG between 14 and 15. Avg speed 25

Note: Just got the R, only two fill ups so far. Fuel economy is roughly 5 to 6 MPG less than my 1999 VDP with the 4 Ltr. normally asperiated engine under similar conditions. Generally, the lower the avg spd, the lower the avg mpg, which indicates more time in stop and go traffic. We will be taking the R on a 1400 mile road trip in December so it will be interesting to see how she does then.

 

Such actions in defense of the marque are not "dick" moves at all.

 

1998 XK8 4.0 Convertible 56,000 miles
95% Hwy/Rural 5% Urban (um traffic isn't an issue in this part of the world)
top down, sport mode, heavy foot, hobby is passing geezers in corvettes
22 MPG US specs

 

In my 2005 XK8, I drove from Richmond, VA to Denver, Salt Lake City, Reno, Mill Valley, CA and then returned by way of Cheyenne, WY and Princeton IL to Richmond. - 6,132 total miles, 28.3 mpg, 57 avg. mph - all from the trip register and speedometer. - lots of interstate driving and also plenty of local in town driving but very little with top down (It was 106 degrees in California.) I almost always use 89 octave gasoline, but I was faked out once somewhere in the west where the "mid" choice was 87 octane.

 

Hi all,
97 xk8 4lt
Almost all country driving at legal speeds (rarely above 70mph) but through hilly country on pretty ordinary roads and no short runs. 27mpg very consistently.
Alan

 

Convertible
4
8
Mixed
US gallons
Sedate driving style, but never fearful of leaving the pack if they are too slow.

Average speed 42 MH
Average MPG: 23.6
Use Premium, but not afraid of regular

 

2001 4.0 coupe

Just completed a 1200 mile tour of northern France and averaged 27.5 mpg. Mostly motorway with a top speed of 120mph (short blast to get past traffic) and coastal roads around Normandy beaches.

Before that trip I had averaged 23mpg over a 12 month period. Not a lot of motorway driving as we don't have any in Suffolk! However, I cycle to work and don't use the Jag for short trips. If I was to drive to work, particularly in winter, my mpg would plummet.

 

I have a 4 litre XKR convertible that is driven on mixed roads and I don't care what mileage I get.

If I ever figure it out, I'll let you know. Also a spreadsheet tracking engineer here.

 

I know this is an old thread but i recently did a 2,000 mile trip to Germany / France and at speeds 90mph - 130mph with consistent runs of 110+mph the 4.2 liter gave me 26mpg.

This was with a passenger and a loaded trunk with the heater constantly on.

I also did a sort trip here in the UK and since I already got my fair share of license points i set the cruise control right at 70mph. Over 100 miles i got exactly 34mpg!!!! Shockingly good fuel efficiency

 

Took a road trip and got around 17-18 average between city and highway. Hit 20 on one tank, highway only. She (2000 XKR Coupe) actually seems to be getting slightly better mileage as I put more miles on her. The was right at 34K when I got her, 40K now.

 

Well I am pleased that I am now seeing 23.9 MPG on a run . If only I did not engage WHOOSH where I see 2.5 MPG I think I could be getting more

 

I have kept records since August 2010.The car is run on 95 octane.Let's say drive split 60:40 between city and country.Average is 11L/100K,or imperial 25.68mpg or US 21.38mpg.
Rob Seignior, Australia, 1997 BRG coupe XK8, 111,000kms/68,972 miles

 

Any updates? Very interesting as I am lookin g to purchase soon.

Also if you could I think you should put the median and the standard deviation. I think that would give a better overall estimator as the median would be the most likely value and the deviation would show how much variability you can *expect*.

 

2001 4.0 Convertible. 26 MPG at 75 MPH, 19-20 in the city at 45-50 MPH. I only run Sunnoco 93 ultra fuel.

 

2002 XK8 convertible. Mixed roads, driving normally to keep with traffic and a bit quicker on dual carriageways (lol) seems to give an average of 21mpg (UK).

 

for datapoint purposes...

2003 XK8 coupe, 4.2l driven regularly by me since late October or early November, with most miles being the ~80 mile round trip to/from the office plus a road trip to Austin at least once a month (~160 miles each way).

Originally was using the discount from Kroger and putting in their 93 octane...typically saw 26-27MPG. The drive to the office has about 50 miles of the 80 mile trip at a legal 75 which means I typically run about 82MPH.

Recently I got added to an Exxon Speedpass account. On a trip to/from Austin, I saw 30.3MPG running mostly 75MPH and I also saw 30.0 on a trip to the dealership for service (~60 miles).

For comparison on both MPG and performance, I ran a tank of Exxon mid-grade through the tank and the same general driving routine saw the tank get less than 25. Could be an anomaly but I'll go ahead and stick with the premium.

When I started driving the car after dad passed, I did not reset the A-side and was doing my readings off the B-side, which I reset each tank. At the time I began driving, he had about 3500 miles on the A-side with 24.5MPG but he would have had more local included in his mix and he was not a typical 'mash it to go point A to point B' driver. I had that beyond 25 before the recent battery replacement, at which point data was cleared. At present, the current tank is close to empty and is close to 28MPG but they had me sort of babying the transmission due to the TCM flash that was done.

So, for the tl;dr version: call it between 27-30MPG with mostly a highway drive at speeds running between 70 and 82MPH and using Exxon Supreme.

 

After performing cooling system fixes, intake system fixes, cleaning the TB and changing the fuel filter, my mileage has jumped from 17/23 to:

25 City
32 Highway

I was shocked to see and then calculate those numbers to see if the computer was wrong.

Whoever said V8s are inefficient was wrong.

I'm using Shell V-Max 91 octane.

 

1998 xk8 coupe. I've been getting 14.4 British mpg around town.

My usual average is 16, but I haven't been on a motorway since my battery went flat and my mpg got reset.

Using standard 95 petrol.

Edit:
After reading some of these comments, I'm going to try cleaning the throttle body, and anything else I can find suggestions for.

 

I gave my throttle body a bit of a clean with some aerosol TB cleaner and went on a roughly 10 mile test drive, averaging 21.3mpg (UK) so I'm very happy.

I'm going to research exactly how to use that TB cleaner properly and maybe give it another go in a few days to see if I can get a bit more out of it.

Assuming I can keep this up, at current petrol prices I've saved myself 13p per mile ( using http://www.fuel-economy.co.uk/calc.html )

 

Now that I have had my XKR 6 months things are looking up. Average MPG is now 24.5 give or take o.1 and on that flat 9 mile run at sea level can get 29.5. if I do not use WOOSH ...