It's to do with power delivery - high torque low down in the rev range gives good "driveability" and puts a smile on most peoples faces.

A big V8 petrol does the job but costs an arm and leg to run - a small capacity turbo petrol does the job, is cheap to build and cheap to run.

Good design and control systems ensure there's virtually no turbo-lag.

Well Jamie i will add another dimension to this if you really are contemplating change, remember i run a still lovely '96 MB E320 coupe, one of the last W124 coupes made, like your Jaguar it has a 6 pot engine but a 3.2 inline 6, mated to a 4 speed simple point and squirt proper auto gearbox and most importantly driving the correct wheels, the rear ones.

In my MB and your Jag you just point it where you want to go step on the throttle and the car simply surges away in either ultra smooth gentle waft mode or in the same ultra smooth way but constant seamless hurtling acceleration depending on far down the throttle has been pushed, all controllable all easy and no drama or fuss.

Now i've seen fast FWD cars being driven quickly and have done so myself, and without fail they disappoint in that they are always crude, constantly scrabbling to find grip unless the road is bone dry, and causing snatching torque steer type effect as one wheel slips then another causing the traction system to constantly cut in, simply horrible.

My sons mate had a lot of tuning carried out to his Cupra, damned thing didn't stop snatching and fighting for grip till it got up to 4th gear, that on Goodyears not Chinese ditchfinders, wouldn't have given you a thankyou for it.

Then you have the usual FWD gearbox problem, either it will be a manual which is fine except you have to drive the damned thing constantly, not too bad with a tourquey NA engine with enough swept volume but add a turbo to the mix and its frustrating beyond endurance having to work around lag and lack of low rev pull, then all of a sudden the power unleashes and off we go, fighting the scrabbling tyres on the way, and 3 seconds later need another gear, just like Mondeo Diesels then, what a palarva compared to your present car for any sort of driving, yes some of the new smaller engines being supercharged and turbocharged might be more flexible but at what cost in long term durability i wonder.

Most of them might have some sort of fancy semi auto gearbox of some sort if thats what you want, but chances are it will be a jerky piece of satans design work that will spend half its time being reflashed by your local dealer and be throughly unpleasant when it is working.

MB seem to have got the smaller blown petrol engine sussed by supercharging as in C180/200k, some rather tastier things they have offered too over the years, such as the C32 AMG (also found in SLK body), with the 3.2 V6 gently supercharged and producing 354bhp mated to a proper auto box for motoring heaven.

Course you might be heading to AWD, but i suspect cutting the VED costs is going to be one of the criteria which will rule out Subarus or anything else with proper engines regd after Mar 06.

Edited by gordonbennet on 06/01/2013 at 23:21

What no-one has mentioned about the obvious engine for Jamie (the Volvo T5 which also sits in various Fords) is the magnificent burble. Whilst V6s have a lovely banshee wail, as my old Subaru Outback had (there's an idea for you Jamie!), standing outside a car with the T5 on song is just lovely. It reminds me of a throaty V8 but with greater response.

I wouldn't describe to 5 pot as gruff-it has even firing intervals and the crank assembly is reasonably well balanced-way better than a four I was surprised at how smooth it is. It's just the consumption...

The direct injection engines currently available offer a superior engine responsiveness, refinement and economy compared to the indirect injection 2.5T so they are well worth looking at.

Twin scroll turbos,electronic wastegate control and downsizing give the responsiveness and improved economy. Direct injection is a gimmick-handy for the manufacturers to improve their HC/CO emissions which can be a problem on turbo engines. As far as the driver is concerned, there's a bit more knock resistence, but that's it. Lots of potential problems with direct injection. The Japs haven't taken to it like the Europeans and I can see why. 70 years of not living up to expectations.