Top Tier vs. high octane

My car requires regular gas, that’s what I use, and it runs well. Every once in a while, when I’m feeling flush, I’ll stick in a tank of premium because it seems like running higher quality gas for a few hundred miles probably gives me somewhat better gas mileage. Though I haven’t calculated it, it is probably good for the car. My brother says that’s ridiculous. What do you say?

I’ve consulted with many experts on this matter because I hear this argument often. They all agree: Putting higher octane fuel than the manufacturer recommends does not improve performance or mpg.

By the way, higher octane does not mean “higher quality,” as you suggest.

What is regarded as the higher quality is gas that has a higher level of detergent than the minimum required by the EPA. For years now, car manufacturers have argued that the EPA’s standards (in effect since the 1990s) regarding detergent added to fuel is not sufficient for today’s vehicles. And many of them recommend using only “Top Tier” gas in their vehicles.

AAA did some rather exhaustive research and concluded that using higher-detergent fuel (versus higher octane fuel) — the gas that is labeled “Top Tier” because it has a higher level of added detergent — reduces engine deposits.

Indeed, that research found that non-Top Tier fuel resulted in 19 times more carbon deposits in the engine (and such deposits reduce fuel economy and performance, especially in newer vehicles) after 4,000 miles of simulated driving.

The Top Tier fuel averages about 3 cents more per gallon than gas that isn’t. But some of the purveyors of Top Tier fuel are often cheaper than the average in a particular area. Furthermore, Costco, for example, sells Top Tier gas, as do some convenience store outlets.

It’s not hard to come by. About onethird of the nation’s stations sell it, and it’s available across the country.

Among stations that sell Top Tier: Diamond Shamrock, Cenex, Citgo, BP, QuikTrip, Sunoco, 76, and Valero.

The full list of nearly 50 fuel purveyors is available at TopTierGas. com. Click on the “licensed brands” tab to access the list.