Well done, If you drive well and smoothly, using torque and taking advantage of hills and coasting in gear on overrun as much as possible...and keep your speed below that at which you start to shift too much air and gain too much tyre drag its amazing just how economical any vehicle can be.

I drove a modern full size but lightly loaded Scania artic from Northampton to London, delivered at 2 inner urban stores and returned back to base with empty stillages/cages, drove satans box in manual override keeping revs to under 1100 rpm and never went above 50mph, when i got back the display showed 15.1 mpg, i was sad enough to take a pic of the display as that was my best ever figure in an artic.

When i drive a same model Scania tanker @ 44tons on one particular journey where almost every roundabout and junction leads to a long hill climb to get back up to speed on the loaded out journey, by the time i get back it averages around 5.5 mpg.

Edited by gordonbennet on 15/04/2013 at 21:41

Trouble with those big engines is they sound quite delicious when being pushed, the harder they work the more throaty they sound and that accompanying constant thrust via a proper gearbox is seriously addictive...thank goodness my old MB is running on LPG, can let my addiction enjoy itself..;)

I average about 23mpg, but somewhat worse than that is possible.

Edited by gordonbennet on 15/04/2013 at 21:46

I knew a bloke who had a normally-aspirated XK (4.2 I believe), he said getting 30mpg was quite common

My dad's experience of that engine was 20mpg-on a very good tank. Some of that could be attributed to the BW 3 speed auto, but still...

It's true that you can tease reasonable economy out of pretty much anything under optimum conditions, but tootling along at 55 renders a big engine pointless-and the fun factor is nil.

I think you can have more fun working a modest engine hard than nursing along a bruiser. Of course, if your pockets are deep enough, thrashing a big engine is best of all!

If you were running LPG you'd easily get the petrol equivalent of 45mpg then. If you do 10,000 miles a year four years or so you'd have saved the cost of a 6cyl conversion. After that pure profit. If you do a higher mileage payback is even quicker. No noticeable loss of power either. LPG's a great way to run a big car cheap.

Surely the point of this discussion is not entirely about saving money - some of it is about saving fuel? After all, fuel is a disappearing commodity, We can always print more money, as the govt has recently illustrated.

Of course it is fun to enjoy the sound of a rorty engine, but it can also be fun seeing just how economical it can be.

Correct me if I'm wrong, but isn't that a direct injection engine? In which case LPG is a moot point.

>Bit of a switch from Mazda to Jaguar though, it must have been quite a change

Actually I went Mazda6 -> Volvo 440 -> XF as the Mazda got written off last year. The olvov was a stop-gap car.

So even more of a change! I only did the comparison with the Mazda because I had owned for a longish period of time and was designed & built this century. Comparing the Jag with a car designed ~30 years ago and built 18 years ago wasn't fair really....

cheers

Stu

After seeing the headline figures on this website for the 3litre xf petrol i plumped for a 2008 3 litre Luxury xf petrol (thinking 26mpg isnt too bad at all).

Big mistake, i get 12mpg in city only! Cannot afford to run it with those kind of figures, my fault for buying the car really as i thought the figure of 26mpg included city driving but obviously not. :(

i got 29.7 mpg on a 32 mile run on A roads last week! so nothing wrong with the engine (has full jag serv history)

anyone else got city only average for one of these?