I drive a standard (manual) transmission car (Miata) and have noticed an uptick in my mileage based on two factors.
- One, I no longer drive in rush hour traffic, or at least not at the height of rush hour. This is not possible for all drivers, but idling bumper-to-bumper is not the way to save gas. I'm fortunate that my boss allows me to leave the office before traffic gets really bad (assuming of course I've come in on time and gotten my chores done).
- Two, and more importantly, I drive slower. I am able to set the cruise control for some of my drive, and I do so at just one-tick (2.5 mph) over the speed limit. If I drove the standard 10 miles over (which is the MINIMUM for most people here in Houston) I would only shave 1 minute off of my overall commute. But that's a theoretical
1 minute, because my driveway does not open directly onto the freeway. There are lights, stopsigns, and other cars with which to contend. Sacrificing the theoretical minute has allowed my average gas mileage to go from 23mpg to 28mpg, a 20% improvement
. Yes, I'm often the slowest car on the road (even going over the speed limit), but I don't feel too bad about that as I watch gas prices climb. It is no longer a threat to my masculinity to allow another car on the road to pass me.
As for some of your other points:
- Wind resistance increases with the square of speed. Therefore, the slower you can safely
drive (eg. just over the limit here), the less resistance your car must overcome and more efficient it will be.
- With few exceptions, the slower an engine turns, the less gas it burns. Therefore, the lowest gear in which you can operate your car will be the one that is most fuel efficient. The exceptions are "lugging" the engine (which is when you stomp on the gas in a low gear and the engine chugs for a second or two before revving-up) and automatic transmissions (which is only a partial-exception because you can't always control what gear the tranny will pick). Simply cruising in a high gear doesn't necessarily dump more gas into the engine, but lugging it can. That extra fuel doesn't burn completely and vaporizes out the tailpipe (along with your gas mileage).
- Cruise control is most efficient in areas of gentle grades where it smoothly applies power. In hilly terrain, the cruise control may force an automatic transmission to downshift as it climbs a steep grade.