Coasting as a High-MPG Strategy
Soap Box Style
My favorite gear is neutral. Every chance I get, I run with the engine off and the ignition switch on. My kids call it driving "Soap Box Derby" style. They are all Soap Box Derby racers. We own three All-American soap box derby cars, and I am a race official. We have been doing this for five years. So you can see, coasting downhill has become a family hobby.
|Attorney Bob Barlow with his manual Honda Civic Hybrid. Barlow maximizes his mileage by turning off his engine and coasting as much as possible.|
I use every downhill slope to coast with the engine off, especially if I can stay above 40 mph—even if I can coast only for a couple hundred feet. Of course, if a green light turns red ahead of me, I immediately turn the engine off and coast. There is no sense in burning gas, even small amounts, if I am going to stop anyway. However, if the battery charge is particularly low and I have uphill slopes ahead of me, I will sometimes use downhill slopes and deceleration to a stoplight to get a little extra charge in the battery to fuel my IMA.
Another trick I use is to coast UP hills with the engine off if I have enough momentum to crest the hill without going too slow. This turns what would normally be very negative mileage miles into very positive miles. I use the backside of the hills to regain my speed, usually with the engine still off as long as I am not impeding or blocking traffic.
I also use the cruise control every chance I get. I shift from first to second gear at 5mph, to third at 20 mph, and at 25 mph I engage the cruise control and use the resume/accel button to get up to 30 mph when I shift into fourth. I use the cruise control resume/accel button to accelerate further and before I get to 40 mph, I shift into 5th gear. I continue to use the resume/accel button to accelerate further. To me, the resume/accel button provides a smoother, more gradual acceleration and uses no more gas than the engine can burn efficiently. It’s more efficient than my foot wants to be. On relatively level ground, I will even use cruise control in fifth gear in 25 mph zones to get great mileage.
Driving my HCH makes me a more patient driver, except when I hit stop signs, red lights and traffic. But when I start out from my driveway or a parking lot, I gently accelerate up to 20 mph or so, and then immediately turn off the engine and coast 100 or 200 yards to the stop sign or first turn, or until I am going slower than conditions require and then I reengage the drive and use my cruise control to accelerate as necessary.
Something for Nothing
|Using his "soap box" methods, Barlow routinely achieves 70 mpg in his Civic Hybrid.|
If you are idling while coasting, you are burning a minimal amount of gas but its effect on your mpg depends on how fast you are coasting. The rate at which you are burning gas at idle is relatively fixed but speed determines how many miles you will get for that gas you are burning at idle. But if the engine is off, every mile you coast is free. Even if you are coasting at 5 mph, and these miles with no gas burned seem to be simply added by the mpg computer, thus driving up your average immensely.
When my friends drive with me, they just think I am obsessive. They know me pretty well.