In article ],
Chris ] writes:
I would like to make a graph of car fuel consumption versus speed.
My driving is not smooth enough to gather the raw data myself.
Do you know of any reliable figures, or graphs?
I'm interested in relative values, rather than those for any particular
car.

I've been playing with this, having recently got my first car
which displays fuel consumption. It wasn't quite what I expected.
Best fuel consumption is flat between 50MPH and 65MPH. Between
45MPH and 70MPH, efficiency doesn't drop off much. Below 45MPH,
efficiency drops off significantly (even when you can comfortably
stay in 5th gear, although I'm not sure it's making any difference
if I stay in 4th instead at lower speeds). Urban driving (start/stop
and never getting above 30MPH) is the worst of all.

Before I actually measured it, I would have guessed highest
efficiency would have been at lower speeds than it is. (The effect
of start/stop driving is no surprise of course.) I suspect engine,
gearbox, etc has probably been designed for good fuel consumption
at higher speeds instead, and this is more than countering increased
drag up to 65MPH.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]