SUMMIT COUNTY If youve been pumping mid-grade gasoline with an octane rating of 87 because your owners manual calls for that minimum, youre probably wasting money.Prices have reached record highs, climbing to an average of $2.32 per gallon in Colorado this week for regular unleaded gasoline. Midgrade, or 87 octane, usually costs 10 cents more. But most consumers dont have to pay that extra 10 cents or $2 to fill up a 20-gallon tank for the higher grade.While most owners manuals recommend a minimum octane rating of 87 and most of the nations gas stations dont offer anything less than 87, gas stations throughout Colorado sell 85. Thats because an 85 octane rating at high elevation (including Denver) is equal to an 87 rating in the Midwest, or other low-elevation regions, said Jacob Bournazian, an economist with the energy information administration of the Department of Energy.Most four- and six-cylinder cars that are designed to run on 87 can run in high altitude with 85, Bournazian said. Most consumers that purchase higher octane fuels most likely are throwing money away.Max Smith, shop foreman at Summit Ford in Silverthorne, has been running his wifes late-model Explorer on 85 octane from the day they bought it. It has about 80,000 miles on it, and he plans to run 85 through it until the day he gets rid of it. He says 75 percent of his customers use 85 octane, and he hasnt seen any ill effects from it.I would imagine anything with a recommendation of 87 would run fine on 85, Smith said. Were thin enough on air up here that youve really got to stress a vehicle to get it to knock.Oddly enough, in high elevations some vehicles ping or knock using high octane and stop when consumers use lower octane which is the exact opposite of what people are taught, said Bryan Harman, service director at Silverthorne Automotive Group.He sees a difference, especially in Subarus, in cold weather. When Subaru owners use lower octane, engines tend to run better, start easier and avoid engine light problems, he said.
Octane ratings indicate the gasolines ability to resist engine knock. Knocking or pinging sounds in engines result from the fuel-air mixture burning unevenly. Raising octane levels delays the residual gases that remain in the cylinder block from igniting. The higher the octane, the longer delay in residual gases. But at high elevations, an 85 rating maintains the same time delay as an 87 rating at sea level, Bournazian said.There are a lot of misconceptions about octane, he said. High octane wont get you better miles per gallon, and its not better for your engine. Its strictly blended for anti-knocking.However, knocking or pinging can destroy an engine within a week, he said. If a vehicle knocks or pings with low octane, especially at high speeds, consumers need to increase the octane rating they use, he said.
Some vehicles require higher octane gasoline, despite high elevation. Performance vehicles and older vehicles may not get by on 85. Anything older than a 1994 model may need the recommended 87 (or higher) rating, especially if its a first-generation fuel injected vehicle or has a carburetor, Smith said.AAA recommends talking to your mechanic about your specific make and model, said spokesperson Mary Greer, who started using 85 octane for her Volvo after talking to her mechanic.Kimberly Nicoletti can be reached at (970) 668-3998, ext. 245, or at firstname.lastname@example.org.