I mentioned in the comments on this post that I managed to increase the mileage in a Ford Expedition last week from 14.0 to 15.6 MPG highway using a hypermiling tactic. It turns out there is a name for the tactic: DWL or Driving with Load.
For the cross country skiers out there, it’s very similar to how you’d approach a hilly ski trail: hit the hills hard, then back things off a bit as you climb, finding a comfortable pace where you won’t go anaerobic. Once you crest the hill, ramp things back up and accelerate on the downs. This is different from how cruise control will handle the road by dropping the accelerator on the ups and backing off on the downs.
In this case, I simply monitored my RPMs using the up and down buttons on the cruise control. As the engine started to rev on the ups, I’d slowly walk down the speed, perhaps losing 5MPH by the top of the hill, then I’d walk it back up to speed on the down. In the end, my average speed was the same as it would have been leaving the cruise alone since I’d go slightly faster on the downs and flats to make up for the ups.
Over the 400 miles between Chicago and Minneapolis, this saved around 3 gallons of gas. Over a year, it would save around 90 gallons of gas, or around $19 per month at today’s gas prices in an Expedition.
CleanMPG.com has a lot of great tips on how you can beat the EPA ratings for your car, including a more complete explanation of DWL:
DWL: Driving w/ Load: Instead of relying on CC (Cruise control) to maintain speed, you rely on your iFCD (Instantaneous Fuel Consumption Display) and accelerator pedal for those automobiles that have them to stay locked in at a given fuel economy. One example would be when climbing an overpass. Instead of holding a steady speed up, over, and down the other side, you allow speed to droop as you climb while maintaining load or FE on the ICE and climb back to initial target after the decline on the backside. Begin the overpass climb at 65 mph, drop off speed as you climb, reach 62 mph at the crest, increase speed on the decline back to 65 mph. The technique depends on elevation deltaâ€™s and traffic conditions. This can be simulated in a non iFCD equipped Accord or other automobile by locking in the accelerator pedal when approaching the overpass. Just hold the accelerator steady into, up, over, and down the back side at the same exact angle while arriving at the same initial target speed after the overpass has been cleared. There are slight accelerator pedal changes that can maximize the technique for those with iFCDâ€™s but the locked down accelerator will work well for those just starting out and with a lack of an iFCD. An even easier easy way to understand the technique is to drive like a roller coaster coasts over the peaks and through the troughs. Pros are increased FE over any small terrain delta with a minimum of work. Cons are that there is thought and user input involved as well as slightly lowering your overall average speed to a given Point B.