Mark Phelan from the Detroit Free Press recently raised that question. He asks "Should you care how much detergent is in the gasoline you buy? How can you even tell?"

He reports that leading automakers BMW, General Motors, Honda, Toyota and Volkswagen think you should care, and they want to help you find stations that sell the cleanest gas. They want some fuels certified as best for fuel economy and emissions.

The automakers formed a consortium, Top Tier Gasoline, that certifies retailers as meeting their standard for detergent. They say it's necessary because detergents prevent deposits of leftover material from building up in engines and exhaust systems. The deposits are like the ash that remains in a fireplace, and their presence in your car's engine can reduce fuel economy and performance.

Top Tier also certifies there are no additives that reduce catalytic converter effectiveness. Top Tier stations account for just more than 50% of U.S. gasoline sales.

“We strongly recommend Top Tier detergent gasoline to keep your engine clean,” GM fuel specialist Bill Studzinski said. “Fuel economy, emissions and acceleration all suffer when there are deposits in an engine."

Just like a fire leaves a pile of ash, burning gasoline leaves residue in an engine, said Matthew Mio, associate professor of chemistry and biochemistry at the University of Detroit Mercy. The residue is like the plaque that can clog your arteries. “Leaving untreated buildup reduces the efficiency of an engine over time. Detergents take the plaque away.”

The Environmental Protection Agency has required detergent in gasoline since 1995. It set the current standard, called Tier 2, in 2000. Top Tier argues that the standard is dated and insufficient for today’s engines and emission systems and also for the more fuel-efficient models on the way.

“The ability of a vehicle to maintain stringent Tier 2 emission standards has been hampered, leading to engine deposits which can have a big impact on … emissions and driver satisfaction,” according to Top Tier Gas’ website.

All gasoline has some detergent. Top Tier certification is the only way to know if what you’re pumping meets the legal minimum or a higher standard.

The automakers who don't participate in Top Tier fuel are satisfied with the current standard. No surprise there.

Phelan noted that any gasoline retail group can ask Top Tier to evaluate its fuels. Many leading retailers have Top Tier certification, but many don’t. They don’t necessarily have less detergent, but they haven’t been independently certified.

What do you think? Is this a lot of hype and marketing, or, should there be simple information to identify the detergent content --or lack of it-- in the gas that powers your vehicles? And should your state require all gas stations to be Top Tier certified?

Or, is this simply too much regulation?