Supermiling, or, How I Averaged 38mpg

This morning, on my way to work, I stopped at the gas station for a fill-up.  As is customary, I enter my milage using Twitter and MyMileMarker, which texts me back my average MPG.  My tachometer (or, taco-meter, as I like to call it) odometer [thanks, Topher!] was at 399 miles.  I was sure I’d be putting 11 or 12 gallons in, as I normally get 30-32mpg, maybe 34 on a good day.  I was utterly surprised when the pump stopped at 10.5 gallons.  I even topped off the tank just make sure it wasn’t a fluke.

A fairly recent pastime for some (following the introduction of the Toyota Prius) has been Hypermiling.  Lately, I’ve realized that by driving over 70mph every day to work, my gas milage has plummeted to around 30-31mpg.  I decided to start taking the back way home on M-52 and M-36 through Chelsea (home of Jiffy cornbread mix).  It’s all 2-lane highways through a state park and somewhat hilly farms.  It takes 10 minutes longer, but it is much more pleasant that the freeway and for when I’m not in a rush.  This change alone, going from 74mph average to 55mph average has made a big difference.

Some other things that I have done:

Shift early, accelerate slow.  The RSX has a i-VTEC engine that varies the amount of fuel injected based on RPMs.  The owners manual recommends shifting at 3000rpm.  However, I found that I can accelerate with minimal throttle when I shift at 2000rpm.  I used to be a late shifter, regularly exceeding 3000rpm.  I also found that my engine switches from 2 fuel injectors to 4 per cylinder when it crosses the 2800rpm threshold.  Keeping below 2800rpm in 5th (top) gear puts me at a comfortable 61mph.  

Coasting.  A big boost to mpg comes from coasting instead of braking.  The high compression ratio of my engine makes for more effective engine braking.  When coasting in gear, the engine uses zero fuel as it can rely on momentum to keep the engine running.  When parking, I turn off the engine early and coast into the driveway or parking spot.

Accessories.  I read somewhere that accessories consume about 2% of a car’s efficiency.  I only use the air conditioning when I need it.  I also use my iPod/headphones instead of the car stereo.

Hard core hypermilers go to lengths as great as tailgating semis and “pulsing” the engine - accelerating up to 55mph, then shutting off the engine and coasting.  That’s probably not a good idea on Michigan freeways, where people commonly whiz by at 80+mph.  

It’s been a lot of fun trying to optimize fuel economy and it’s made a 19% difference already.