Nick Finnigan
have similar fuel consumption at 50MPH and 70MPH
There are several issues:
1) "Official" figures are more accurate than the "onboard fuel computer", just as "official" speed measurements are more accurate than those of in-car speedometers.
2) Using "official" figures (I hope yours are that!) shows that the difference in fuel economy is 6MPG better (40MPG) better at 56MPH than at 75MPG (34MPG). Is that 18% difference? These figures are not "similar", let alone the same.
3) Do I have a problem believing the 37.5MPG at 70 v. 38MPG at 50? You bet. I have no idea where they come from.
4) Do I care about the difference? Well, it's nice to be accurate.
I've just had a look through the back of my Cavalier "Driver's Manual". At the back, it shows fuel consumption at steady speeds. Copying the figures, we see:
Model: 1.4S 1.6i 1.6s 1.7D 1.7DT 1.8i 1.8 2.0i %difference 26 31 24 36 37 29 30 27
This an old car, like the one above. The differences are greater, unless I've boobed on the calcs, if so please help me out!
What of the ludicrous claim that a modern car is "VERY LIKELY" to be more economical at 70 than 50? I'd still like to see some "official" figures that back this up - however, I'm sure that none will be forthcoming.
If anyone can be bothered to post figures for newer cars, or a link to the same, I'm sure it will be very interesting.
