[Fursty Ferret]

Try it?

There's no difference between cheap and expensive diesel other than the placebo effect and possibly a tiny bit more detergent which will benefit ancient French engines.

The energy density between the two is the same (in fact, in V-Power diesel it's actually slightly less), so you won't get more power. You may (possibly maybe) get slightly more torque from the higher cetane rating igniting and burning faster but it's academic and at the expense of increased particulate emissions. So if the car has to burn off the DPF more often then this will offset any fuel saving.