In 1995, the Environmental Protection Agency (EPA) introduced minimum standards for all gasoline sold in the U.S. These standards included a detergent package that must be added to gasoline to help prevent the accumulation of carbon deposits, mostly on the intake valves, which can impact engine performance and emissions.
Whether the 1995 standard is sufficient or not is still open for debate. When it was first introduced, some gasoline refiners actually reduced the detergent content in their fuel because they had been providing more than the new mandate required. Many have suggested that fuels with lowered detergent content, used over the long term, can adversely affect driveability and emissions.
But some vehicle manufacturers—including General Motors, BMW, and Toyota—took a different route and joined together to establish a higher standard which they called “Top Tier” gasoline. Gas stations that use this Top Tier gasoline include Chevron, 76, Mobil, and other major players in the business. (Stations that might use the lower standard include Costco, Walmart, and your local non-affiliated station.) The fuel sold at these Top Tier stations costs a few cents more per gallon.
Each retailer of Top Tier gasoline has formulated their own detergent package to meet the higher standard. Their additive package is added to the fuel after it is loaded into the fuel delivery truck at the refinery. For example, fuel sold at your local Chevron or Costco retailer is essentially the same. In some cases, the fuel may even come from the same refinery. The only difference is the detergent package added to the Chevron fuel once it has been loaded on the delivery truck.
With the rising price of gas, I know the question in most people’s minds is this—“Is the more expensive gas worth the extra price?” That is a difficult question to answer. I have personally visited the Chevron refinery in Richmond, CA and toured the lab where fuel testing is performed on gasoline engines. I have seen the results of their testing and heard their claims.
Do I believe carbon deposits are formed on the intake valves? I certainly do because I have seen them.
Do I believe Top Tier gasoline does a better job of removing these deposits and keeping the valves clean? I do.
Do my vehicles receive a steady diet of Top Tier gasoline? They do not.
My vehicles have been performing quite well using the less expensive fuel blend mandated by the government. They receive an occasional dose of Top Tier fuel, but that’s it. Is this the right solution for all vehicles, I cannot say. It could very well be that some engines are more prone to the effects of carbon deposits than others. If you decide to use gasoline meeting only minimum government standards, there could be consequences down the road. Carbon buildup is a slow process and engine performance may degrade very slowly over time.
Perhaps it is not necessary to use a Top Tier gas at each fill up, but then again, it may not be such a good idea to always use the cheapest gas you can find. Just like a varied diet is good for your body, a varied diet of fuel should be good for your vehicle. And if you find a particular brand of fuel that does not agree with your vehicle, avoid it, just as you would avoid a particular food that does not agree with you.