Absolutely not. They cost more to buy, so how long would it take to get your £1000 back in fuel costs? Diesel is now £1.40 a litre. Would we see 45mpg on short trips, town driving? Probably not.
Obviously, if you are a mile muncher then it would be a consideration, but tbh if you were a mile muncher you would be looking at something even more frugal / comfy. Possibly German?
Its a none starter 'im afraid. Look at the Megane DCi 175. Good car, but were are they? You never see them / hear of them.
In my experience "hot" diesels are not that frugal. I had a Pug 206 GTi HDi which returned 32mpg with mixed driving. I had it mapped to 130bhp and lots of torques and the economy did improve, but not by much. In gear, say from 30 / 40mph it would destroy my 200 even though it had a BHP deficit of about 50BHP. The problem was it ran out of puff, and that is the problem for most hot diesels.
My mate has a Toyota Auris SR 180 Diesel. He has had that mapped, and if you tied it to a tree it would pull it clean out of the ground such is the torque. He gets 27mpg mixed and he went on a run to the lakes and got 37!
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Smaller F.I petrols with new technology is the way forward.
I loved my "GTi HDi" for what it could do and hated it for what it couldn't. Hill's were the best! It would fly up