Having completed treatment and rinse phases in this car and now it's back running on fully synthetic Ii decided to track MPG variations on a regular drive.
I undertake this drive in identical test conditions (as I always leave late evening or early morning when it is cool and no traffic).
model year 96 (in the uS you say MY97) with a replacement engine in 2004 30k miles on new engine External Temp = 5-10 degrees C mileage distance = 350 (2 x 175) duration of each leg = 3hrs 10 mins Gasolene = 100 RON (super unleaded note in the USA I think that's 97.7 MON) No stopping excepting at end of each 175 mile journey Both cold starts (as I'm visiting my Mom I have to stay don't I!!)
Previously I was achieving 28.2-30.1 MPG and in the two most recent runs since the ARX treatmet I've achieved 33.4 MPG and 34.1 MPG
Now previously I thought I'd been getting good gas mileage for a 4ltr V8 but now with the increase averaging 4.5MPG (circa 15%) I reckon that's close to an extra 75 miles per tank.
I'm shortly to convert the Jag to run on LPG which should mean that I can do the same journey at half the cost. UK super unleaded costs £1.04 UK per litre or $1.97 US so to fill up at this rate stateside would cost you circa $74 from empty (So think about paying $7.48 a gallon the next time you complain about gas prices!)
Note that to fill this car with UK gallons =16.5 which equates to 19.8 US gallons...nice to have something in the UK that's bigger than you have across the pond!!
Mark on behalf of Auto-Rx thank you so much. MPG here in the colonies is a 'bugger' for the natives if you have no objection would like to post this on Auto-Rx web site. Await your answer. Frank Miller
1) The two most recent runs following te ARX treatment were in a fully laden car with two passengers and boot (you call it a trunk I think) fully filled. I estimate that this added an extra 300lbs in weight and should in normal circumstances have a detrimental affect on the best economy.
2) The figures quoted are all from the cars trip computer (which as many will appreciate isn't always that accurate) however since it's been used for all runs the same degree of inaccuracy would apply.
3) I am used to driving economically as my other car is a sensodrive/semi-auto trans diesel Citroen C3...I don't beleive you have these in the US but in over 30k miles of driving it's returned 62.4MPG (and yes this recently has also had an auto RX treatment and I'm on the rinse phase at the present). I am used to coasting to a stop or on downhill stretches where there really is no point in keeping your foot on the gas. That being said this amazingly economical car has climate/auto lights & wipers Sat Nav and even a chilled glove box.
4) The MPG figures experienced in the XK8 are considerably higher than the manufacturers quoted figures by some margin. Indeed even the later generation 4.2 XK8 only had a quoted extra urban figure of 34 MPG and I acheived my results with 10% urban (sub 40 MPG) driving.
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