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Saving Lots of Fuel with Scott: Pulse and Glide in a Hybrid

Hybrid Hypermiling using P&G

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2007 Nissan Altima Hybrid left side

Nissan Altima Hybrid: A great car for Pulse & Glide

photo © Adrian Gable

I've been practicing hybrid hypermiling for awhile now, and I enjoy it as much for the knowledge and skills I gain as for the fuel it saves me. The techniques and tricks of hypermiling (the quest for extreme fuel mileage) are many and varied, from Forced Auto Stop (FAS) and Ridge Riding to Potential Parking and Pulse & Glide (P&G). Each technique has its time and place for use throughout the course of a trip (whether it's a ten minute jaunt into town or a several hour cruise across state). Some are easy to learn and execute, while others take a bit of patience and repeated use to master. But it's well worth the effort and time. The first hypermiling trick I spent time learning was FAS (Forced Auto Stop) because, in my opinion, it returns the best results for the effort of execution. FAS is a good start, but there's more: To gain the other big chunk of fuel economy that hypermiling offers, Pulse & Glide must be added to the arsenal.

Pulse and Glide: For Hybrids Only

This is pretty much a hybrid only technique--I'm not sure how it could be done in a regular vehicle (though I wouldn't be surprised if some diehard hypermilers have developed a method). To initiate a P&G, accelerate to about 40 MPH with the engine running (the pulse part), then ease off the pedal until the engine shuts off and the hybrid system goes into electric mode. At this point, the vehicle's power meter should show zero (or if equipped with an energy flow monitor, no arrows are showing energy flow). This is the glide part. The engine is off, the electric motor is disengaged and the vehicle is literally coasting for free. When the car slows to about 25 or 30 MPH (depending on traffic conditions, of course) repeat the pulse part, then the glide and so on. If properly applied, this trick uses the engine only to accelerate, and it never has the chance to idle along, wasting fuel while providing no return. It sounds harder than it really is, but it does take time to master, and requires a lot of patience and regular practice. And in my opinion, this technique has a more limited use than FAS, which is especially effective in hilly or sloping terrain. Where P&G really shines is on flat secondary roads where traffic is light and speeds are low.

I'd been practicing the technique for a few weeks when I decided to dedicate a trip to concerted P&G efforts (with a little FAS thrown in) to see how far I could stretch my fuel mileage on a trek that I make with some regularity. I decided to make the 34 mile (all country roads) round trip visit to dear old Mom and Dad. In my 3.0-liter 5-cylinder diesel Benz, I can get about 26 mpg on this trip with just normal everyday careful driving (no jackrabbit starts, no speeding, and gently coasting to a stop). As a baseline for this experiment, Christine ran the trip in our hybrid (2008 Nissan Altima) without any hypermiling trickery. In fact she drove it pretty much like I drive the Benz (gently) and she averaged just a tick over 34 mpg. Seasoned hypermilers can easily double a given hybrid's EPA estimate, so I knew that I had to best that by at least 25 or so percent (giving myself lots of cushion--being a neophyte and all), or I'd be quite disappointed.

P&G Fuel Economy Trip Du Jour

I hopped in the Altima Hybrid, reset the FCD (fuel consumption display) to zero, started it (the vehicle was cold, so the engine kicked on after a couple of seconds, eating into my precious fuel economy number right off the bat) and started out on my hyper FE (fuel economy) quest. The first mile of the trip is a twisting uphill climb--and the car was cold--so the engine was running the entire climb. I went light on the accelerator to help keep my average FE as high as possible. The road finally levels out just after the first mile and by the time I was able to lift off the throttle, the hybrid system was warm enough to allow the engine to shut off. Oh goodie, I was now ready to do some serious pulse and gliding. The maximum speed limit on most of the roads on this trip is 45 mph, and except for the first mile, they are relatively flat--perfect conditions to P&G. The beginning mile of all engine power had me down to a measly (in my opinion) 25 mpg average FE--I had my work cut out for me.

For the next 16 miles I took as many opportunities as I could (depending on traffic flow) to accelerate up to 40-45 mph and then coast down to 25-30 mph on every flat section of the road available to me. On sections of the road that were hilly, I used the FAS technique as well. The game of hypermiling is a bit of a tease (ya wanna know how well you're doing all the time), but I tried to keep my eyes averted from the FCD, so I could concentrate on driving. The occasional "I can't help myself" peek did reveal continually improving mileage though--a nice incentive. All of this driving at slightly slower than average speed added about seven minutes to this normal half hour trip, but the end result in fuel economy was well worth the time penalty. As I pulled into Mom and Dad's driveway, I took a final glance at the FCD and much to my glee, saw that I was able to turn a 34ish mpg jaunt into a 56.2 mpg junket. Wow!! A 60 percent gain, and I was more than satisfied. Had I not done it myself, I likely wouldn't have believed it. And then, just to eliminate the possible "flukeness" of it all, I employed the same efforts on the return trip home. Not quite as good (guess I got a little antsy somewhere along the way), but still a respectable 54.3 mpg. Not a bad day's work.

Find more fuel saving tricks in Hypermiling in a Hybrid.

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