I bought my 05 XJ8L a few weeks ago and have just manually calculated my 1st mpg result...a dismal 21 for combined freeway/streets.
I know the "L" is only 50lbs heavier than the standard wheelbase, so it should not contribute to the dramatic lowering of the published 28MPG.
And I am not a lead foot driver at all.

Any advice/tips would be greatly appreciated!

Cheers,
Wolfy
Los Angeles

 

I get around 24-25 mpg (UK gallon is larger), from my XJ6 which has the 3 litre V6 same as the S-type. On long runs it gets up to around 28, so I dont think your car is exceptional at all.

Only way to really check it out is to leave the trip computer running on 'A' setting over a few thousand miles and see what it pans out to. Then for a long freeway run, measure this using 'B' and compare the two.

 

I get approx. 26mpg on winter gas (gas made more volatile - even CA has it) and 27.5mpg on summer gas with 65% freeway and 35% city - I do drive calm but do maintain 70ish on the freeway. Denmark (Europe) where I am from does not have winter gas and the millage was actually better in the winter than in the summer - just curious - Fraser Mitchell do you have winter gas in England? I do accelerate moderate without being annoying and I back off to make car shift into higher gear and I do coast a lot - this car is very good at coasting:-)

 

you wont get 28MPG unless its all highway.. I average 19-20 around town and I am a spirited driver, (I enjoy the skinny pedal too much, which is one reason I had to get rid of the XJR, LOL)

 

I hardly ever get on a freeway. I work around 5 miles from my home. I average between 14 and 17 mpg. kthrash, bet you can guess why my mpg is so low! But I was prepared for this going in. I couldn't be happier as I go whisking around, gobbling up long stretches of road in astonishingly short time.

 

I'm at 22-23mpg for mixed driving. I've only had it on the road a couple times and it got over 26mpg. I'm sure it could get close to 30mpg for hwy only driving.

 

I'm at about 20mpg - more city than highway though (lot's of short trips). I did get 30.6mpg while driving from Austin to Dallas - on the trip computer (about 1-2mpg optimistic).

Here are my stats for the last year or so:
Details: Jag - 2007 Jaguar XJ8 Fuel Economy - EcoModder.com

Mine is a 2007 swb is rated at 16city/25 hwy by EPA and your's seems to be rated the same: Compare Side-by-Side

Remember that they changed how they calculated the mpg a couple of years ago.

/Mike

 

Fellow Jag owners, should we be concerned about MPG?

I won’t be till gas is above the $5 mark in the US.

 

Maybe not concerned with it. But I do like that the car is efficient for its size and power. It's great that it can go 500 miles on a tank.

 

you are lucky over there we are paying the equivilent of about $9.30 a gallon over here !!

 

I got 30 MPG on the last tank, 100% highway driving on a long trip.

 

I get 26.5 mpg combined average. on an all hiway trip 28/29. once did an all hiway trip where i got 31 (calculated by tank fill up, not the trip comp.) but i never went over 70 and the a/c was off and the windows closed. wasn't trying to be a cheapskate just had to take my time to avoid arriving early. I didn't buy my xj because of its excellent fuel economy but I'll be the first to admit it's nice to have a car this big that's this comfortable that looks so awesome going down the road.AND gets unbelievable gas mileage. I've had this car for just over three years now and I still get a big smile on my face when I get behind the wheel.
It's not how fast you go, it's how you go fast.

 

I beleive the UK petrol refiners alter the petrol components mix to suit the seasons, but there are not separate pumps for summer and winter.

 

Thanks Fraser Mitchell - interesting to know - I would not think this is necessary with fuel injected cars actually for most cars I could imagine it would causes problems with the emission system - maybe this is to accommodate the carbureted cars still out there. My car sometimes has problem starting after fill up with winter gas dealer states normal - too many fumes accumulates in the evaporative canister and due to pressure escapes in the intake and causes hard start.
Compared to most fuel mpg's I most drive like an old man

 

Took a 2300 mile trip this fall in my 2007 XJ8L.

Cruising at 75-80 miles an hour on fairly flat terrain yielded 27.8 mpg.
A 466 mile cruise through Indiana to St. Louis gave a fantastic 29.5 mpg. That stretch was pretty flat and I drove between 65 and 70 miles per hour.

My typical around town, with some highway is typically 22 mpg.

I always calculate my mpg with every fill up. This lets me know how the car is performing on a weekly or so basis. Oh, and my figures are using the math, not the cars guesstimate.

Better mileage was also seen when I got out of Texas and tanked up with the 100% gasoline vs. our local 10% alcohol stuff.

Tor the size of this car, I'm more than happy with it's performance and economy.

 

I get 14 mpg in city with kick down at every red light, and I get 26-29 mpg on highway doing 65, I have 97982 miles on the car, just replaced the spark plugs with NGKs.

 

90% highway driving with occasional traffic, I am getting 25 mpg for past 5,000 miles

 

1974 XJ8, 47,000 miles

I also calculate mileage at each fill up. In-dash computer is always about 2 mpg better than actual. For 21,000 miles I have averaged 21.4 mpg. Always try to get 0% ethanol. High point: 28.9 mpg - Low point: 14.6 Note that the cold weather in Wisconsin knocks the heck out of the mileage!

Jag is driven to Florida each year and the mileage is about 27 at 70 mph.

 

Going to work I average about 24 around town and some freeway. All interstate on cruise control it consistently gets 34. It is unusual that the tailpipes stay clean inside, they have no carbon coating on them. My XKR is the same way. I think the car is very efficient. I have an Audi A6 Quattro that averages 19. I just guess that the 4 wheel drive causes more load.