James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
Wheels:
Gary writes by e-mail:
“I know you have stated many times, as have other writers who have columns in the paper, don’t buy premium gas if the engine doesn’t call for it. However, with warm weather, I have heard that buying premium will help the engine computer, which is trying to really retard the timing more than normal. So, what are the conditions when buying higher octane is the correct thing to do?”
Halderman: Purchasing different grades of fuel depending on the seasonal temperatures dates back to the days before computer-controlled engines and fuel injection. Today, the grade of fuel is determined by the vehicle manufacturer for each engine. For most vehicles, regular grade unleaded 87 octane fuel is the fuel that should be used regardless of the weather or temperature.
Some vehicles “recommend” premium fuel for best performance and fuel economy. In this case, using a midgrade (plus) or even regular may be considered safe to use but the fuel economy may be less. If the vehicle manufacturer recommendation states that premium grade is “required” then I would recommend that only premium grade be used. Check the owner’s manual for the exact fuel to use.
All gasoline is blended for each season and often varies throughout the year. This means that fuel purchased in the early spring may not be suitable for hot summer driving. The same goes for fuel purchased in the summer, which is not designed to allow for easy starting in cold weather. For best results, gasoline should be used and not stored either in a storage container or in a vehicle longer than 90 days (three months).
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