CLICK & CLACK : A Real Gas

Sunday, September 2, 2007

Q Dear Tom and Ray:

My husband and I have entered into a heated debate about the quality of gas. My less-than-informed husband insists that gas from quick-stop gas stations is a lesser quality than that of the big oil companies. My supposition is that there are only a few oil-refinery companies in our country and that "all gas is created equal." We are in agreement that there is a difference among octane. Could you please let us know which is best to put in my car? -- Anne

A TOM: The only difference between gasoline brands is in the contents of the "additives package" used. The stuff you buy at Fred's Gas & Herring comes from the same holding tank as the stuff at Chevron, Shell or Texaco. But some brands use additives that do a better job of keeping your car's valves and electronic throttle clean.

RAY: Back in 2004, several big carmakers -- GM, Honda, Toyota and others -- were unhappy with the detergent performance of gasoline, because they were finding deposits inside their engines. So they created some new gasoline standards that are tougher than the federal standards. They called the gasoline that meets these higher standards "Top Tier" gas.

TOM: Companies that voluntarily sell only Top Tier gas in the United States are: QuikTrip, Chevron, Conoco, Phillips, 76, Shell, Entec, MFA Oil, Kwik Trip/Kwik Star, Somerset, Aloha Petroleum and Texaco.

RAY: So you won't find Joe's Gas and Step Stool Emporium on that list. Exxon, Mobil, BP, Gulf, Amoco, Sunoco and Hess are also absent.

TOM: Does it matter? Honda, BMW, Audi, VW, Toyota and GM think it does. But if you use the gas with fewer detergents and end up with carbon buildup after 100,000 miles, you can often get rid of it with a few cans of engine cleaner or by using Top Tier fuel for 10,000 or 20,000 miles. So it's rarely irreversible.

RAY: But if you drive a high-end car, or you want to be sure you never get any buildup on your fuel injectors or valves, you have to use Top Tier gasoline at least most of the time.

TOM: One other thing to keep in mind: The list of Top Tier providers might change. To see the latest list, go to their Web site,

Dear Tom and Ray:

Last night, my neighbor asked me if I had left my car running for a reason. I told him that I had turned off the car and had the keys in my pocket. He said, "Well, your fan has been running for an hour or so, and real loud." He was right. I put the key in, turned it to the "accessory" position without starting the car and then switched it back off. The fan finally stopped, but the car would not start the next morning without a jump. A few times in the past three months I have returned to my car in a parking lot to find the stereo playing while the key was still in my pocket. Clearly, some switch is staying connected when it should be off. Where should I look first? -- Brad

RAY: If it had just been the fan, I might have suggested a faulty fan timer, or something like that. But when you threw in the fact that you come back to your car, and it's listening to Jimmy Buffett all by itself, I think it has to be a bad ignition switch.

TOM: It's allowing accessories to draw power from the battery without the presence of the key. It's acting as if you left the key in the "accessory" or "start" position, even though you didn't. That's what killed the battery.

RAY: Have your mechanic test the ignition switch. He'll do that by unplugging it while the fan or the radio are misbehaving. I'm guessing a new switch will solve the problem, Brad.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them by visiting the Car Talk Web site at

2007by Tom and Ray Magliozzi and Doug Berman

© 2007 The Washington Post Company