I'm a very practical and frugal guy, so the first time I ever heard about hypermiling (driving techniques for superior fuel mileage), I figured I gotta know more. A friend mentioned to me a news report he read about hypermilers who can get well over a hundred mpg from a Prius, and even 50 mpg from a regular old Accord sedan. This news really appealed to my pragmatic nature, so I set about learning the techniques and tricks of the hypermiling elite. Not knowing anyone who could show me the ropes, I became an ardent student of hypermiling via the internet. I read descriptions of tricks like pulse and glide, forced auto stop and ridge riding from enthusiast blogs and websites, and then tried them out, rather tentatively at first. But as I became more skilled, I could actually see the results in my vehicle’s FCD (fuel consumption display) as well as when I calculated my mileage the old fashioned way (fill the tank and divide gallons used into miles traveled). I'll say right upfront that I find it much easier to execute hypermiling tricks with a hybrid than with a regular internal combustion engine vehicle. And I've done it with all kinds: an old '83 diesel Mercedes, a '94 4x4 manual transmission Chevy pickup--and some newer stuff too--an '08 Crew cab Chevy , both an '07 Toyota Prius and Camry, and a pair of Nissan Altima Hybrids (one each '07 and '08). Not only is it easier to hypermile with a hybrid, it's infinitely safer.
The Forced Auto Stop (FAS)
The first technique I learned and tried is Forced Auto Stop (FAS), but executing a FAS in a regular car takes a soul braver than I. This task involves coasting down a hill with the car in neutral and the engine shut off. What? Too difficult to control, and WAY too dangerous for my taste—with the engine off, the power brakes and steering are compromised and the steering wheel could lock. No Way! I've tried a similar trick that involves only putting the car in neutral to coast, but leaves the engine on. This method at least keeps the power steering and brakes fully functional, yet allows a slight increase in fuel mileage since the engine is only idling at 700 RPMs instead of perhaps rolling at 2500 RPMs.
The trick, and in my opinion, the Achilles heel of a FAS, is putting the car back into gear to resume acceleration. I've learned that I need to do a rev match (accelerate the idling engine to match the freewheeling transmission speed) so the tranny gears and clutches don't detonate when the slow rotating engine and fast turning tranny re-engage. Just as important though, maybe more so, a proper rev match keeps the drive wheels from momentarily locking up at the moment of re-engagement; loss of control on a slippery road is a real possibility. I think these concerns are slightly moderated with a manual transmission and clutch, but only slightly. I also wonder how this might affect internal transmission lubrication (at least in automatics), and further, how a continuously variable transmission (CVT) would react to repeated engagement and disengagements. Personally, I don't think it's worth damaging a very expensive component for questionable return. I've heard stories of folks using this technique for years with no problems, and that may be, but at best it's a roll of the dice.
FAS - Hybrid Style
This brings me back to my original point of hypermiling in a hybrid—it's really not even forced at all—it’s actually just an AS (Auto Stop). Approach that same downhill slope and when the vehicle speed is about 40 mph or less, the engine will shut off automatically as the accelerator is released. Now, the hybrid system is in control of the car. Electrically boosted power steering and brakes continue to operate and speed is somewhat moderated by the computer (via regenerative braking) which directs coasting momentum into electrical energy for storage in the hybrid battery.
This is how I like to take advantage of a full hybrid’s ability to save gas. I let the car coast whenever possible by looking far down the road ahead of me and anticipating upcoming road and traffic conditions. For instance, when I see a hill coming up, say half a mile ahead, I'll begin to gently accelerate before hand so that by the time I hit the hill, I've built up enough "steam" to climb the hill with very little "foot in the throttle." Just as I crest the hill, I lift off the throttle and coast (as the hybrid system goes into AS) over the last bit of peak and down the other side. Of course the hybrid system has already turned off the engine, so I'm "runnin' free."
The watch-phrase for hypermiling (no matter what technique is being employed) is “be patient, plan and anticipate.” I really can’t stress it enough--and I've found that taking advantage of every little (or big) opportunity to coast (AS) whenever possible seems to have the largest single affect on my fuel mileage.
Find more fuel saving tricks in Hypermiling in a Hybrid.