Had a great road trip just a couple of weeks ago. I usually drive Speed Limit +9 or 10 mph. (Sigh..... my radar detector has died. No "ECM").

I-95 was clear except for some ocassionally serious rain.

Pulled into the gas station with 502.6 on the old odometer and an average speed of 75 mph! OK, .... true, there were only 18 miles left on the Range read-out and she took 18.1 gallons to refill, but still.... This is only the second car I've owned that's busted the 500 mile barrier. The other was a 280ZX with a 20+ gallon tank (Nice!). BTW: The Computer's MPG read-out said 28.4.

On the return trip I had a 29.7 mpg / 76 mph leg! Would have done well over 500, but it was a scheduled stop. She was running GREAT!!!

And then (why is there always an "and then" to these stories?) the little hose from the supercharger to (what seems to be) the fuel pressure regulator came off completely -

I wonder if the good-runnin's will continue, or if they were just because that hose was coming loose? When the hose did come off I had simultaneous P0171 & P0174 codes (both banks lean).

And life with "Kitty" goes on. Gotta love it!

 

The best on my XKR has been around 24 mpg on I20 @ 75 mph from Shreveport to Dallas. Most of the times it's 22/23 if I don't run it hard.

 

Thats amazing. Went from RI to Delaware and got 24-25 mpg and I was ecstatic.

 

With my '97 XK8 I got 25.3 average for a 320 mile trip all highway except for about 30 miles of in town.


Dave

 

I have done the Los Angeles to Berkeley run on one tank about 410 miles but I can't keep my foot from exceeding 75mph.

 

Made the run from Carrollton (North Dallas) to Galveston, TX on a tank with some to spare. A little over 315 miles, but didn't note the miles left to go on the readout.

If memory serves, she got about 26-27 mpg each way at 75 mph.

 

I think I've topped out at 25mpg at 75mph. They just upped the speed limits around here to 80mph and now I'm down to 22-23 mpg in my 2001 XKR convertible

 

I used to be able to drive between Denton (near Dallas), TX to Vicksburg, MS, which is a little over 400 miles on one tank of gas (about 24 mpg) but then I changed the rear axel ratio from a stock 3.06 to a 3.27 and now the best I can get is about 18 to 19 mpg.


Mark

 

Idaho has an 80 MPH speed limit? Sweet! Yup, .... there go your MPGs.

I did have a leg once that averaged over 80mph (crossed most of PA at 90+) and the MPGs weren't as bad as I had expected (25+) until I hit an hour long traffic jam. That run was made with my 130K mile engine. The latest numbers are with the 60K mile engine that replaced it. Performance has imroved.

Again: it is possible that the recent efficiency has been due to that little hose just being loose and leaking for a while prior to disconnecting completely. Still, I'm surprised that there is such a difference between my overall performance numbers and those that you all have listed. After almost 50K miles driven since I bought the car I've averaged 23MPG (total miles driven / total gallons of fuel consumed) and I've averaged a speed of 47 MPH. I guess I drive about 2/3 or 3/4 highway.

BTW: I put an ounce or two of Mavel Mystery Oil in the tank at each fill-up. Every vehicle I've treated as such has benefited in some way. Any of you who decide to give this a try, please let me know the results after a few tanks.