Took a little 200 mile run today and decided to be uncharacteristically dicipline and strictly observe the speed limit. The purpose, just to see how much I could squeeze out of gallon from a 400 bhp pump!

Topped off the tank in Keystone South Dakota with 91 premium, a/c on, sport mode off, conv top up. Ran at 70 for about 45 miles, then 60 for the next 155, guessing my average altitude was around 4000MSL, temp 75-80F. Engine oil Mobil 1 0w30, used cruise control for entire trip.

Result....26.9mpg according to the onboard computer, I think I would have made 27, but I had already reached my destination.

 

That is impressive!!! I just rebuilt my motor and I guess I love the sound of the exhaust and keep it in Sport mode too much... Sport mode is 18.2 MPG and Normal is 19.5 MPG...

Thanks for sharing!!!

Cheers!!

 

I'd call that worth the difference!

 

When driving for economy (not something I indulge in too often!), using the Instantaneous Fuel Usage display function on the Trip Computer helps balance the choice of optimum throttle, braking and acceleration. This instantaneous reading updates every three seconds.

Graham

 

FWIW
I just completed a 1000 mile week end trip in my 07 XK. From the trip computer I got 29.9 mpg. Mostly Interstate driving at 65 to 70 mph with 1 passenger plus luggage.. I would expect you to get a few miles less with an R. Under similar conditions my old 05 XJR would do 27/28 mpg. BTW- I use mid grade gas. Super high test produces better results but not enough to cover the added expense.

I recon you are on target. Aluminum bodies with 700 lbs less weight, a 6 speed transmission and great aerodynamics produce outstanding results..

 

I don't think your car weighs about 3100 lbs.

 

Steve,

The original specs. on the 07 XK Coup puts the weight at 3600 pounds. Jag stated at product intro that the same car rendered in steel would weigh 700 pounds more.

What's this 3100 pounds you refer to?

 

The steel bodied XKR weighs just over 3800 lbs. So with your comment that the aluminum XK is 700 lbs. less would mean yours is only 3100 lbs.

It sounded like you were comparing your car to the OP's XKR concerning fuel mileadge.

 

The 6spd helps a lot and at cruise speeds an 8 or R doesn't seem to matter much.

On long highway trips I've gotten 28 or 29mpg in my 03 XKR, in spite of the fact that its made put of lead and granite and all that other heavy stuff.

 

driving on a long stretch of flat & level pavement last year at 70mph, 2003 XK8 with the top down, the instantaneous reading held steady at 27.x mpg.

supposedly there's an approximate 1-2mpg difference between the XK8 & XKR. not sure how much having the top down would affect fuel economy.

 

70 MPH on the pavement! This MUST mean something different in the US.

We have 'pavements' for pedestrians and roads / highways / motorways for vehicles in the UK. I thought in the US you had 'sidewalks' for pedestrians and highways / freeways / interstates for vehicles.

Where does 'pavement' come in?

Graham

 

I frequently drive from the San Fernando Valley to Delano, CA, approximately 120 miles with little traffic and at speeds between 70-90mph (posted speed limit for most of the way is 70), in sport mode (as I have never driven the car out of sport mode) and have averaged anywhere from about 26-30 mpg when it's just the highway driving. Compared to my Buick Enclave, that is at least 10mpg better, and certainly much more enjoyable. And by the way, that is with the top down as I have it down nearly all of the time. I call my 2002 XKR, my economy car. I paid so little for it, and it gets excellent gas mileage.

 

pavement/asphalt/road are used more or less interchangably in the yanklish language

I remember having a similar miscommunication a few years ago when I told a Brit friend that I refueled my tank with "gas" rather than petrol.

 

"Pavement" is a concrete road, laid out in segmented slabs with strips in between to allow for expansion.

Asphalt roads are made of (guess what) and a newly paved asphalt road is much smoother and quieter than a "pavement/concrete" road.

I'd say that most roads in the US are asphalt. Pavement roads surely last a lot longer, as long as they are on stable ground, and you don't get potholes.

A little known fact is that the Interstate Highway system in the US is actually the......Construction

The Interstate Highway System was authorized by the Federal Aid Highway Act of 1956[14]—popularly known as the National Interstate and Defense Highways Act of 1956—on June 29.

and that one of the primary purposes was for our military to be able to move their equipment around in case of attack. The bridges over it were designed to give enough clearance to be able to fit tanks being carried on trucks or other military equipment underneath it.

 

I used to get 24 or 25 mpg in my 2002 XKR but with my new 3.27 rear axel ratio and LSD, I'm only getting about 21 mpg when driving on highways at ~70 mph with the cruse control on. However, the new axel ratio makes a hugh difference in acceleration, especially 0 to 30 mph that it's more than worth it in my book. The first couple of times that I stepped on it when a stop light turned green, I almost scared myself it was so quick.

Mark

 

Top down on a long trip is pretty consistently 2mpg less in my case. Got a chuckle from the "pavement" remarks, out here in South Dakota we have in order of quality the following:-

Oil roads, aka Blacktop, asphalt
Pavement, as the man said concrete
Gravel
Dirt, yep really!

 

Yep, we have all of those in Louisiana, but I won't drive my Jag on the Gravel or Dirt roads. Here we actually have some Swamp roads, but that is another story altogether.

 

I'll throw another road surface in the mix:
Chipseal - Wikipedia, the free encyclopedia

this really isn't too bad after it gets worn in from lots of traffic, however until it does it's worse than gravel because the stones are so tiny they kick up very easily and have the same effect as a sandblaster using very coarse media.

 

Long ago abandoned in the UK, the French still love this technique for road repairs. Driving along it is like being peppered with a shotgun.

Graham

 

Return trip netted 28.5mpg, had a slight tailwind! Actually had the average mpg up to 29.2 atone point, but the last 45 miles were four lane (dual carriageway) and the increase from 60 to 70 brought it back down.