Doctor Diesel

Thirsty auto

Web04We’ve had a Ford C-MAX Titanium 2.0 TDCi 140 automatic for some months now, from new, after many years of petrol motoring, and we’re disappointed with the fuel consumption. Initially we were getting around 45mpg on decent runs, but now it seems to have slipped back and we’re only getting a little over 40mpg. Your assistance would be most welcome. Most of our motoring is open-road in flat country, and we don’t hit much urban crawling, which surely should be helping the fuel economy?

A difficult one this Mr P. Your car uses the rather excellent Powershift automatic transmission, and I have to say that many people find it does tend to encourage fairly enthusiastic driving. If had you told me that you were getting less than 40mpg and found that disappointing, I would have a great deal of sympathy. But the EC combined figure for your car (and we know how difficult it is to match) is only 51.4mpg, and frankly you are getting not that far off what I might expect. One might, however, have expected your figures to have improved a little though as the engine freed up.

But you don’t mention what you were driving before the C-MAX and what transmission it had. We all drive quite differently, and I often suggest (politely, of course!) that some diesel owners who suffer from poor economy haven’t yet learned how to drive diesels what I call properly. Revving the engine regularly towards 4,000rpm and beyond gives poor economy and also gives the engine an unnecessarily hard time, with little benefit in real life performance. The Powershift, as I said, changes gear up and down quite freely and I’m wondering if you had a rather sluggish automatic before and are used to putting your foot down fairly hard to get the car moving and not using the diesel engine’s characteristics to best effect. Try going a bit more gently on the accelerator and letting the car ease into the higher gears earlier, and you may find that you get an improvement in fuel consumption. Keep an eye on the tachometer, ease off when you see it heading towards 2,500rpm, and it will change up and drop you into a more economical engine speed band. When I’m driving an automatic diesel, I like to try and find a steady accelerator position that sees the engine speed climbing from 1,500rpm to just beyond 2,000rpm before it slips up a gear, and I think this is the best practice for a medium rate of acceleration, when you’re not in much of a hurry. Try it and see, although in your case, with the peak torque at 1,750rpm, aim for a change up at around 2,300rpm. Let me know how you get on.
Doc D

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