Not flaming you! It, to me, when someone wants true highway mileage, means, for example, traveling down 95 to Florida . You gas up, reset computer, get on highway, drive till you need gas, get off, gas up, and either calculate mileage or reset computer after noting its mpg ave.
many of the real highway mpgs are very low on the new cars because its not true highway, its more based on your driving situation with a lot more variables which hurt mileage.
Example my 2008 BMW X53.0Si was rated 16/23 in the old system. It is now rated 15/21. I routinely get 23mpg on highway at 75.
Old rating system for my 2004 XJ was 18/28, new system its 16?/25. It is easy to get 28+mpg in that XJ.

 

Very helpful - thank you!

 

What are y'all so worried about fuel economy in an XK or XKR? You don't buy these cars for their mileage, you buy them for their fun factor! The difference in mileage is peanuts. Here's why:

Case 1: 400 mile trip @ 24mpg = 16.7 gal x $4.00/gal. = $66.80.
Case 2: 400 mile trip @ 20mpg = 20.0 gal x $4.00/gal. = $80.00.
Case 3: 400 mile trip @ 18mpg = 22.2 gal x $4.00/gal. = $88.80.

Many XKRs are driven on nice days only, with less than 4K miles per year. So, the 6 mpg difference in fuel would cost only $220 per year (see above 400 mile trip example: $88.80-66.80=22.00x10=$220). That's just over $18 a month, or around 60 cents a day! So, if you can't afford the fuel, don't even think about buying the XKR.

IMHO, driving my XKR is well worth the incremental cost; the pleasure is priceless - the exhaust sound, handling, instantaneous power, upgraded features and styling (quad exhaust, larger grille, nicer interior, etc.). If the purchase price of the XKR is within your means, do it - you won't regret it! But think twice about getting a 2009 Portfolio with Alcon brakes (like mine), because there is no spare tire - makes me a little worried to stray too far from home.

Can't beat the return on investment - I get twice the smileage from my XKR than my cost of mileage!

 

It sounds as if you're expecting results from some kind of controlled study based on your response. This is an owner's discussion forum! You might have to scale back your expectations ... a notch.

 

Stuart, it has nothing to do with the cost! It has everything to do with accuracy. Above that, it has to do with actual range per tankful. I for one, only stop when I need gas on long roadtrips. I'm quite proud of the fact that I can drive from CT to North Carolina before a gas stop in my XJ. I routinely non-stop my trips between homes in CT and ME. I'd rather drive 6-7 hours and take a half hour+stop, than stop 10-15minutes every couple of hours. Car is wicked comfortable for long trips so why stop?
As far as fair weather drivers, I buy sports cars to drive at least 3 seasons/year rain or shine. An XKR will probably even see a few track days so I can actually drive it for what its made to do instead of driving it like a garage queen. Obviously, with that thought in mind, I can afford the ride. I respect nothing more than seeing premium rides be they Astons, Jags, Ferraris , Lambos etc being DRIVEN espa t a track in a controlled environment where you can actually, safely experience 510HP. You can't do that on public roads if you have any idea of safety.

Wildcat, I appreciate your numbers, thankyou. The numbers I was asking for are not those of a controlled study. In my Lotus forum, multiple folks can tell you precisely what there vehicle gets for mileage, range, etc even on multiple tracks, in rain etc. That is also a owner's discussion forum. It is quite fascinating how differently the conversations on this (and other Jag) forums differ from those of other performance luxury cars.

Doesn't anybody ever reset their trip computer, drive 1000miles up/down the east coast etc and know what mileage their vehicle gets over a long multitank run! This is not rocket science. Kind of scary how few Americans actually know their vehicles' potential be it the driving dynamics, etc.

If you're thinking of driving a 500+ HP car, you better have a clue IMHO. Most Americans can't handle 200HP, let alone 500+. There I said it. American drivers, by and large are BAD!!

 

Scenario: 2007 XK, Continental extreme performance summer tires, Shell V-Power 93 octane petrol, AirCon on, clear weather, usually fullish tank, stuffed 21" duffle in boot, dim-witted fat ol' geezer steering

According to the trip computer:

Central Carolinas Interstate, uninterrupted cruise control @ 65 MPH = 32 MPG (consistently)

Central Carolinas Interstate, uninterrupted cruise control @ 70 MPH = 30 MPG (consistently)

I'd surmise circa 60 MPH might result in the optimum MPG (34-ish?), but haven't checked.

Extended mixed driving averaging 40 MPH = 25 MPG

This car is not a daily driver and has a preference for undulating, meandering rural two lane blacktop devoid of constabulary when wandering aimlessly on its weekly jaunt. 25 MPG avg. ain't bad.

Typically when the tank's full the "range" indicator's 450 miles or more. Me thinks (?) that's the magic box extrapolating historic average MPG performance for several thousand miles to confirm and project about 25 MPG. 'Course it's just a stupid technobox and could be fooled by randomness and not foresee a "black swan" event.

Not being particularly technically inclined, much less competent, one suspects anything less might be a symptom of imperfectly functioning fuel induction or injection. A bottle of Techron every few thousand miles might improve mileage, though it also might increase exhaust tip soot.

(On a leisurely trans east coast drive down I-95 I'd fuel in Va or SC, but I'm parsimonious and it's really none of my business. Izit?)

 

Thx for your response! Those are some fantastic #s as far as I'm concerned. I wonder how much can be attributed to the 93 octange gas...Enjoy the countryside!

 

can you see the display for mpg on the xk?* i did not check this when looking at a 07 xk. on my boss bmw idrive you can see mpg.

 

4000 mile trip a couple of summers ago in 08 XKR convertible (which is probably a bit less aerodynamic than the coupe). As I recall I got around 24mpg overall....but realize that had "some" city as well as "some" triple digit deviations. My speed was probably quite a bit higher than the normal posted limit as the damn thing just seemed to have a mind of it's own. If I were a guessing man (I am) and were willing to go out on a limb (I am) I would say: if you kept the speed reasonable, your foot out of it, and your accepted challanges to a minimum with triple digit forrays infrequent you could probaby get 25-28 (28 would be a stretch in my book though) in the "R" on the road....
around town all bets are off though...I would almost guarantee you that anyone here would have a "problem " getting over 20 around town in a "R"...and I fall back to my only excuse...the damn thing can't help but stay out in front (at least from my own experience :-)

 

My 2008 XK that I purchased last week in San Francisco indicated 29.1 MPG on the readout when I finally pulled off the freeway following a 150 miles drive. That drive did include some San Franciscan slow traffic (probably about 3 miles) and 4 different slow sections on the freeways with some some stop and go traffic. I feel that those who post 30 MPG and over for purely freeway driving are correct. However, not sure yet about the accuracy of the computer readout.

The 05 XK that I just traded indicated a 10,000 miles average MPG of 25.8. However, when I checked the actual usage I realized that the computer readout was roughly 1 MPG optimistic. As to my usage, 90 percent of that 10,000 miles of driving was open freeway.

 

On the 07 XK there are two separate trip computations available, A & B, which are set/reset in the "vehicle settings"(? from a fuzzy memory) tab/subtab video display. (You can save either A or B tabs for extended multi-trip information and use t'other for a single trip, etc..)

The continuously changing computations for A & B trips may be video screen viewed in that tab/subtab category.

Depressing the tip of the lights/turn signal stalk will also display in sequence (with each depression) the odometer, "range": mileage remaining based on fuel level and average speed, avg. mph, avg. mpg (when either trip A or B, not both, have been selected in the video screen subtab). The preceding are displayed between the speedometer and tachometer (rev meter).

When considering an XK/R you really should explore all the functions within the touch screen that may typically be controlled by switches in other cars. That's why center console controls are somewhat sparse.

Newer XK/R may have an updated system.

 

The 07' has been getting around 24 mpg with my fat butt driving most of the time. I have found though, that resetting the trip with the stalk really doesn't and you have to go into the touch screen to do so.

 

Wildcat, that's what I'm talkin about!
These folks confirm my beliefs that an XK, like my XJ, should easily get 28mpg at 75mph. An XKR, I would expect will get 25-27tops, unless you were a real good boy accereating on ramps etc, but we all know that's the line in the sand that we MUST all cross!

 

Thx to everybody for their replies - is is great to see that the trend is towards better than average manufacturer projected mileage for this car. I wish my 2010 MDX could get this kind of mileage (I'd even be happy with getting average projected mileage!).

 

Great observations more in line with reality. My Corvette Z06 can easily get 30 MPG if driven for 200+ miles on the highway and that's hand calculated not using the cars computer which is off by about .6 MPG to the good side. On my 06 LS2 Corvette (lowly 400HP C6) I could get 31 MPG.

Maybe they need to add a third category for pure highway driving, followed by the current highway rating relabeled Hybrid Driving and followed by City. That would be more reflective of the actual environments being rated.

BTW when I pick up my 08 XK next week I have a 300 mile trip from Chicago to my home in southern Illinois. I'll top off the tank, ZERO the Trip A odometer and Fuel Mileage Reading and set sail. When I get home I'll tank up and use the calculator in my BB to see how accurate the car vs hand calculations. I'll report my findings on the car, trip home and my "REAL WORLD HIGHWAY" fuel mileage.

Tom

 

My '07 XKR is showing 13.3 avg right now. I reset the computer a few weeks ago and have only been driving to work and back since. It is an 8 minute commute on flat roads with lots of stop lights, and yes I like to go fast. I have gotten around 23 on highway trips, but unfortunately don't see anything close to that on the little screen most of the time.

 

For my 07 XK I average around 24-25 MPG in mixed driving, on 91 octane gas. With highway driving only I am easily 29-30+ MPG, which has been a very pleasant surprise.

 

Great work folks. Hopefully, everyone reading this now understands what true highway mileage is! So much of a vehicle's efficiency is based on weight that I would fully expect the 28-30 mpg mileage some of you accurately report.
Those of you reporting the 24mpg numbers are doing commuter like drives with a mix of highway and local running say 5 miles to highway thru town, 10-50+ miles on highway, and local running to a destination. Either that or there is some heavy traffic, inconsistent speeds, or just plain non smooth driving involved. My XJ gets 20-24 mpg in that mix of driving.

BTW this is no different than professionals. Some guys/gals are better than others stretching out a tank of fuel in race situations, lifting a little earlier, carrying more speed thru turns (ME!!) which means less acceleration needed on turn exit, short shifting as directed by pit crew etc. Even happens in Formula 1!!!

 

Last Wed I picked up our 2008 XK from a dealer in Chicago, it has 35K miles and freshly serviced. I had him set the tire PSI to ONE pound over recommended. Just before we got on the Highway I spied a Mobil gas station, so I pulled in topped off the tank and Zero'd Trip A. We set sail, lots of irregular traffic until we got to 55 South then we set the Cruise at 71 MPH. We did make three rest stops. When I got home I filled up at my local gas station. Total miles were 295.5, gas to fill the tank as 10.94 which works out to 27.0 MPG. There was no attempt to baby or conserve fuel.

I'm now checking my "hybrid" city/rural" fuel mileage, as a reference my 07 Z06 got 16.9 MPG in this routine. I'm guessing the XK will yield similar results.

I'd say our 08 XK vert get's pretty dammed good fuel mileage.

Tom

 

I just picked up an xkr in Colorado and drove it back to Atlanta. My mileage ranged from 20-25 mpg. My speeds were similar 70-80mph. I bought gas at four different branded stations just to experiment. I also drove one day with the top up and one down.

I don't know what I learned but I did get a little depressed when I realized that I put 10% of the vehicles total mileage on in two days