The thing is tho' you may only be getting 39mpg due to the conditions, but a petrol would just about do that on the long run with all the moons and stars aligned. On a similar journey you'd see mid 20's from a petrol???
My MOT tester, who I've known for 20+ years, keeps dropping hints about wanting to buy my GT, and yesterday was no different. When I got home I'd had an email from the local dealer with some of their offers. I could either knock a £17k hole in my savings and have a new car, or sell mine, have some change from the maximum PCP deposit, pay hardly noticeable monthly payments for 3 years and then be left with a bill for £13k or no car. No thanks. I wouldn't mind changing it for a DSG of some description, but paying much less to change, but then I wouldn't know where the new car had been.
My problem (if you can call it that) is I tend to look after my cars so well that I am reluctant to let anyone else have the benefit of all my efforts, or couldn't bear to see it driven round looking like a sh!t tip. That's why I end up keeping them for ever.