Q: Why is regular unleaded gasoline in Colorado just 85 octane when in other states like Florida it’s 87? If I require 87 octane for my car, I need to buy the more expensive midgrade because we need more octane in the mountain states, don’t we?— Robert Maxwell
A: Actually, you don’t need more octane here; you need less.
The typical octane ratings in our country for regular passenger cars range from 87 to 93 AKI (or anti- knock index) — except in the Rocky Mountain states.
Because of our altitude, the typical engine uses less air, the result of our thinner atmosphere. Without getting into the very complicated science behind combustion and engine knocking, our thin air helps in reducing a knocking engine — you know, the “pinging” you would hear if you hit the gas hard and the engine’s working.
That means the 87 octane your car might require at sea level — and note that this will vary from model to model, so read the manual — will need only 85 octane here to produce about the same performance. That’s why back East you’ll see 87 octane as the lowest available at the pump.
It’s not wise to use the lower octane at sea level, so the 85 in Philly isn’t a good idea for an engine needing 87 octane. But move here from Philly and you should be able to pump in the lower 85 variety.
There’s a key caveat: The bets are off if your car has a turbo engine because they usually can’t produce the necessary power at the lower octane levels.
Things could be worse. The lowest available octane in many parts of Europe is about 91 AKI, and gas is priced by the liter.
Q: It’s become common for store clerks to ask for my driver’s license when I use a credit card, then refuse the sale if I won’t provide it. Can they? — Marie Johnson, Denver
A: Nope. Merchants cannot require identification as a condition of accepting a signed credit card, according to the folks at MasterCard.
If it’s signed, according to card issuer rules, the retailer must accept the card on its face. Report them to your card issuer immediately if the store owner doesn’t agree.
