
Originally Posted by
RKenshin
Unless you're talking excessive, constant speeding (85+ mph on a regular, consistent basis) your MPG isn't affected much at all by it, short of being in an ancient car. 'Optimal' MPG for most cars is usually around 60-75, but the difference between going slightly faster/slower in itself doesn't have that much of an affect on MPG. The biggest factor is break pedal usage in wasting tons of the car's kinetic energy, and people who speed tend to waste far more of it.
Though, yeah... aggressive driving certainly tends to use bursts of gas/breaks, so that was likely the main cause for you.
But speed alone doesn't do much. I'm averaging higher MPG in my Scion than it's rated for and I'm 10-20+ MPH over the speed limit literally like 95% of the time. I should be getting 23 city and 31 highway with an average somewhere in between, but I've never dropped below a range of 32-34 MPG over the past 6 months (I'm still a giant dork that keeps excel sheets on this shit).
If you want to maximize MPG, just try not to waste the kinetic energy of your car. Nothing is worse than the people that feel they either have to have their foot on the gas or the break at all times (both for MPG and driving! so annoying). Bonus: break pads will last much longer too!
Also, if you have a standard you actually will get better MPG without using cruise control and both doing the above + shifting into neutral when you're rolling for longer periods (down a hill, traffic slowing, coming up to a stop, whatever). Those two changes gave me an extra ~20% MPG.