Anyone who regularly works with small gasoline engines knows the basics of how to keep them running - change the oil regularly and keep the air filters clean and you're well on your way. But not everyone is aware that how you manage the oil and fuel you use in your four-stroke workhorses can have a significant impact on machine performance.
The lifeblood of your engines
Without oil to lubricate and cool them, engine parts would get too hot and eventually melt together to cause catastrophic engine failure. But will just any lubricant do?
In a word, no. The first rule of thumb to follow when choosing an engine oil is to use whatever is specifically recommended by the engine manufacturer. This can always be found in the owner's manual.
The American Petroleum Institute (API) issues guidelines for API Service Categories. These guidelines are designed to help you choose the oil best suited for your type of engines. The latest engine oil service category includes the performance properties of each earlier category. The most current service ratings are SL and SJ category oils for gasoline-powered engines. It should be noted that these categories are different for diesel engines. The information in this article will refer only to gasoline engines.
Engine manufacturers will specify an API category oil but they won't usually mandate a particular brand of oil. There are many brands to choose from, and each might have varieties ranging from economy to premium.
"A high-quality motor oil is one that meets or exceeds the latest industry and OEM specifications for a specific application," says Thom Smith, technical director, branded lubricants with Valvoline. "A premium lubricant is one that meets additional specifications beyond the basic industry and OEM specs and/or provides superior performance. Premium lubricants in general provide superior oxidation resistance, superior cleanliness and reduced wear relative to lower-end lubricants on top of application-specific benefits."
In general, higher quality lubricants have higher performance standards and they also burn cleaner.
"SL oils provide the best high-temperature protection and meet more stringent emissions standards than previous ratings," says Mark Nelson, product service trainer for Briggs & Stratton. "You have to have high-quality additives [in the oil] to meet emissions standards. The better we meet emissions, the better our engines perform, which is also a benefit to the environment. It's a win-win situation."
Sources say it's the additive package in combination with the base oils that make a high-quality lubricant. The better lubricants won't break down as fast and won't leave as many deposits.
"One property of oil is to help seal the engine," Nelson explains. "When the oil breaks down, scoring starts to occur. Combustion pressure starts to bypass the piston and cylinder and ends up in the crankcase. Basically, you lose power because the engine doesn't have the necessary compression."
Over time, without proper maintenance, oils will break down and the lubricating properties diminish. Aluminum engine parts can become scored and galling occurs. This is a situation in which aluminum parts melt and form a buildup that prevents parts from moving, causing seizure.
"The junction between the connecting rod and the crankshaft gets the most stress," says Nelson. "When there is a broken connecting rod and scored crankpin on the crankshaft, these are telltale signs of insufficient lubrication."
How do you know if the oil you choose is high quality? Sources agree that following the engine manufacturer's recommendation and API Service Category guidelines is crucial, but so is choosing a name you trust. Also, price can provide a clue. The higher-priced lubricants often provide better performance, as the old adage, "You get what you pay for," applies here.