Monday, June 23, 2008

Hyper Drive

Much is being made these days, unsurprisingly, of sundry fuel thrifty driving techniques lumped together as "hypermiling". Some of the techinques are just common sense, some are not nearly so common, and some are just downright dangerous. Accelerating slowly and coasting as much as possible are two that have been used for many years by the savvy fuel saver but others such as turning off engines when stopped are relatively new and controversial.

Some new vehicles use the engine stop technique but those presumably are designed to accomodate the increased wear and tear of such activity. If an engine is not specifically designed for it, with a heavy duty starter and other strengthened parts, then component breakage costs may largely offset fuel savings. This is one area where electrically driven vehicles have an advantage although it's not a large one. Having an engine stop and start repeatedly in stop-and-go traffic is seriously inadvisable on average engine designs.

Virtually all of the "new" techniques were used back in the 50s and 60s in an event that was a perennial feature of the automotive landscape, the Mobile Econony Run, which pitted "stock" vehicles of most of the manufacturers against each other for mileage bragging rights. Endless mechanical tricks and extreme driving discipline often resulted in fairly ridiculous numbers such as 35mpg for Cadillacs and Chrysler Imperials and of course much higher figures for smaller vehicles. The "winner" was not based on strict mileage but rather how much fuel per unit of vehicle weight was used in the test. This tended to favor larger vehicles so the winner of the event was frequently a large luxury vehicle even though its actual mileage may have been far less than the "compact" cars of the day. What this proved was, well, not a heck of a lot but much advertising "mileage" was gotten out of the results if nothing else. Gas prices were around 25 cents per gallon which is roughly half the price currently adusted for inflation. Still this was nowhere near the historically low prices of the 1990s so many people were interested in the results. I suspect that if such an event were to take place with current vehicles 100mpg plus figures would be common.

Success in hypermiling basically depends on how much hassle is tolerable to the average person and also what type of driving predominates for a given driver. Commutes in slow rush-hour traffic may require a lot more discipline that most are willing to employ and risk slowing traffic even more than otherwise. A whole thruway full of folks ever so gently accelerating and then carefully coasting sounds like an engraved invitation to road rage for the more impatient commuter. Out on the super-slab hypermiling techniques will have less effect percentage wise and may increase traffic speed differentials to a dangerous point. If you, as recommended by hypermilers, allow your car to coast up hills then you may be only going 30 or 40mph over the top which saves fuel but runs the clear risk of being smacked in the butt by an inattentive driver with his cruise control locked on a 70mph speed limit. A more generally effective and much safer method would be to just set the cruise control 5mph below the limit then take what you get and call it good enough because we all know what is the enemy of good-enough.

There is plenty of room between those extremes to do some good on the mileage front but regardless this sort of thing is going to require a level of situational awareness entirely foreign to the mass of the motoring public. People who drive while chatting to friends on the cell, draining a Big Gulp, and noshing on MacNuggets simultaneously are not good candidates for the significant additional mental processing required by hypermiling. There are darn few, alas perhaps, willing to pursue their daily driving tasks in a continuous state of quivering heightened awareness. A lot of folks might find the additional stress a poor tradeoff for saving a few bucks on fuel.

The increased situational awareness of hypermiling could well result in a lower traffic accident rate but trying to use the techniques where they are inappropriate could easily have the opposite effect. A moderate unobsessive approach to the "problem" will pay some dividends but don't expect to save hundreds of dollars per year. Dozens might be more like it. TANSTAAFL as usual. Up to you to decide if it's worth the trouble.


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