Matthew Botos

Sustained $4 a gallon gas is one of the new signs of the apocalypse, meaning it’s time to question the ancient Japanese wisdom of my Maxima’s owner’s manual: “Premium fuel recommended”.

My now vestigial mechanical engineering degree had been able to follow the logic: a high compression engine needs purer fuel to run at peak efficiency, otherwise the engine electronics would just dial it back to a less efficient level. Cheaper gas would just be offset by fewer miles per gallon.

As much as love watching my holdings in energy stocks go up, I decided it was time to put this to the test: would I really get fewer miles out of non-premium gas? My admittedly loose testing methodology: two tanks of typical driving measuring cumulative miles per gallon on a ScanGauge.

The results: 22 mpg on premium, 21 mpg on regular. That 1 mpg is well within my margin of error, particularly given that I did more highway driving on the premium tank. I’ll keep watching the numbers to see if there’s a longer-term decline, but for now regular fill-ups are going to ease the pain at the pump a bit. How does your mileage vary?