Dont buy gas from exxon and

Workers there mix additives mandated by the Environmental Protection Agency into the base gas in order to clean a car's engine and reduce emissions. Then, the different gas companies — both off-brand and major brands — put their own additive packages in the gas to further boost both cleaning and performance.

A key difference is that the major brands put more additives in their gas and claim to have some secret ingredients. This extra shot of additives provides an additional level of cleaning and protection for your engine. But is this extra helping of additives, which jacks up the price, really necessary?

And, if you don't use more expensive, extra-additive gas, how soon will your engine's performance suffer? The real difference is the amount of additives that are in the gas, Nielsen says. More additives essentially afford more protection — but they also cost more. Some automakers and oil companies believe that the amount of government-required additives isn't enough to protect engines. They have created a Top Tier gasoline designation. It means that those gasoline brands sell fuels that provide more and better additives.

Nielsen recommends that drivers look in their car's owner's manual to see what the carmaker recommends and, when possible, follow that guideline. People who are still concerned about gasoline quality can ask a specific oil company if it has performed independent testing to substantiate its claims.

Selling the Secret Sauce in Gasoline The major oil companies spend millions of dollars convincing buyers that their gas is superior by creating ads that feature smiling cartoon cars, lab-coated nerds and sooty engine valves. Buy Shell's nitrogen-enriched gas , for instance, and you won't get a buildup of "gunk" in your engine, company advertising promises. We can see it, feel it and measure it.

Macias says the gunk caused by fuels with insufficient additives can foul fuel injectors and even trigger "Check Engine" lights in as few as 10, miles. But not everyone is keen to talk about gasoline quality and whether additives really make the difference. Edmunds sought comment from one well-known seller of low-price gas: Arco also often finds itself targeted as being a lower-quality product.

BP, Arco's parent company, did not respond to Edmunds' interview request. The American Petroleum Institute provided background comments about fuel additives and promised to provide an expert for an interview. The API spokesman never called back. Finally, Southwest Research Institute in San Antonio, an independent, nonprofit testing facility, also declined to comment on the question of gasoline quality. The Skeptics and Their Tests The Auto Club's Mazor was more forthcoming, and has some interesting results from a blind test he did on three samples of gasoline from both major and independent gas stations.

Mazor believes that the driving public has outdated notions about gas. Twenty years ago, only premium fuel had detergents in it. Back then, it was beneficial to occasionally buy a tank of high-test gas to clean the engine.

Then, he says, "regulations were very lax and there was little enforcement. But all that has changed. Likewise, Randy Stephens, chief engineer for Toyota's Avalon , isn't wholly convinced by the claims of engine protection afforded by higher-priced gas.

He suggested that other oil companies will come back to ANWR if the drilling starts. Overall, he said, the environmentalists' attack today isn't based on facts and it isn't news.

I think a number of environmental groups recognizing the fact that we're not afraid to say what we believe or what we think we've discovered through sound science, see us as a threat. They know we don't play the political game. But there's another agenda at work here, too. Environmental groups have been able to block legislation they oppose in Washington--for instance, to allow oil drilling in ANWR--but with oil industry men as president and vice president, and Republicans controlling both chambers of Congress, environmentalists are afraid their luck is running thin.

The anti-Exxon campaign is a way to open another front in the battle. Rodger Schlickheisen is president of the Defenders of Wildlife.

Going after ExxonMobil is the rational thing to do, because they are the enemy here, trying to influence the White House and the Congress to vote the wrong way on these issues. Jeffrey Berry is a political scientist at Tufts University. He studies the way interest groups operate, and he says this effort outside of Washington makes sense. Lobbying organizations are most effective when they can adapt to changing circumstances.

Conservative citizen groups did this during the Clinton years. The conservatives did it by focusing on spreading their messages through the media.

They key is persistence. Basically, Berry said, the environmental groups have to become an absolute thorn in the side of ExxonMobil, something they're having only mixed success doing in a capital dominated by the Republican Party. Visit our website terms of use and permissions pages at www. NPR transcripts are created on a rush deadline by Verb8tm, Inc.

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