Questions about Gas and Oil

By Brian Klaubert

Question #1 - What grade of gasoline should I be using? The good news is that the majority of vehicles should use regular unleaded. A small minority of very high performance automobiles are recommended to use premium unleaded. These cars have above average compression ratios or have turbo chargers or super chargers. The higher grade fuel actually ignites later than the lower grades. Only high compression vehicles benefit from this delayed combustion. There is usually a sticker by the gas cap recommending what grade to use.

One important myth to dispel is that premium gas cleans your fuel injectors or other parts of your engine better. Thirty years ago this was true, but in the 1980’s congress passed legislation changing this practice. As part of the environmental legislation of that era, gasoline companies were required to provide the same amount of cleaning chemicals in all grades of gasoline. For many years gasoline companies continued to imply in their advertising that premium gas still cleaned your vehicle better. About five years ago the EPA and the Federal Trade Commission made them stop this practice.

It is better to stick with one grade of gas, though not necessarily one brand. Your car’s engine computer constantly “learns” how your engine is performing and slightly modifies its own internal control tuning. If you change the grade of gasoline, changing the timing of combustion, you will confuse your engine’s computer.

Question #2 – What grade of oil should I be using? It is best to stay with the grade of oil recommended by your vehicle manufacturer. Most vehicles use 5W30. Ford and Honda are now using a 5W20 grade oil, which is a thinner oil when hot. These manufacturers are manufacturing their engines with closer tolerances. The thinner oil is necessary to properly lubricate these engines. It also should provide a little better fuel mileage. It is important to use the 5W20 oil if your engine calls for it.

Question #3 – Should I be using special “High Mileage” oil if my engine has a lot of miles on it? The “High Mileage” oils have a very small quantity of a chemical that softens the engines seals and causes them to swell slightly. This is intended to help reduce burning oil at the valve stem seals and hopefully reduce leakage at the external seals. These oils also have some additives that are intended to reduce oil deposits and wear. This oil is not a synthetic oil, and does not have the lubrication and extended life benefits of synthetic oil.

A “High Mileage” oil change costs more than conventional oil, primarily because of marketing costs, not the chemical costs. It is very important to continue to change this oil at the recommended interval. Even though this oil change might cost twice what a normal oil change costs, do not then drive twice as long before changing it again.

I am skeptical about the benefits of “High Mileage” oils. I would suggest that you keep track of your oil consumption once you begin using the High Mileage oil. You should probably trial this for 2 to 3 oil changes. If your oil consumption decreases, great! If it does not, you may want to go back to using conventional motor oil.

Brian Klaubert owns Christian Brothers Automotive – Hamilton Mill on Braselton Hwy in Dacula. They are 2004 winners of “Best of Gwinnett” from both the Gwinnett Daily Post and Gwinnett Magazine.