Putting Regular In Your Premium Car? Think Twice

As we get closer to Memorial Day weekend, there's closer focus on gas prices for the heavily-traveled holiday period.  For the moment at least, fuel flows about 25 cents cheaper per gallon than this time in 2011, according to AAA.  That's also about the current price gap between regular and premium, give or take.

Some drivers are doubling-down their savings.  They've stopped running higher-grade gas in favor of the lower-octane option.  Though as the Los Angeles Times cautions, saving a little now could come back to haunt motorists down the road.

Engine knock, characterized by a metallic pinging sound, can occur when an engine is under load and things get out of sync in the combustion chamber, with misfiring low-grade gas often the catalyst, so to speak.  It's not a beautiful noise, and it's not at all good for an engine's health.

Cars today are equipped with knock sensors to prevent or least minimize this through dynamic engine timing.  So when an engine designed to benefit from premium fuel runs on regular, the immediate driver's seat translation can be less responsive acceleration and slightly lower gas mileage.  Some drivers, having done the math, find they still come out ahead and are willing to sacrifice some horsepower in the process.

Long-term effects are less certain.  Knock sensors, however well they function new, may not perform to the same level after tens of thousands of miles.  Less effective engine management could open the door to internal damage.

Perfect opportunity for a large-scale experiment?  Possibly.  But as Harold Schock, director of the Engines and Automotive Research Labs at Michigan State University told the Times, don't expect it to happen.  Even the EPA isn't about to test how a couple hundred cars fare on different types of gas, short-term and long-term.

There's nothing stopping consumers from trying it on their own cars, though.  The consensus is to check the owner's manual first.  There, Schock says, you'll find "the best set of practices for...the longest life and the best performance."

If the manual suggests premium fuel is recommended, you can probably segue to the cheaper stuff without any drama.  If it reveals premium is required, you probably shouldn't tempt matters.

If it's any consolation--especially to the latter crowd--the interviewed engineers agree there's more to be saved through proper maintenance and sensible driving than cheaper gas can deliver.  Besides, a 25-cent per gallon difference on a 15-gallon fill-up only amounts to $3.75.  Something to ponder over that $6 cup of coffee.

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This story originally appeared at The Car Connection.