Definition of flash point according to Google: “The temperature at which a particular organic compound gives off sufficient vapor to ignite in air.”
Occasionally we see folks pointing out the flash point values of 2-stroke oils, claiming that a higher flash point number is superior to oils with a lower flash point. The implication being that 2-stroke oils with a lower flash point will burn off prematurely at high operating temperatures, leaving engines vulnerable to damage under heavy loads. The short answer to this debate is that the flash point does not matter and here’s why.
Once 2-stroke oil comes in contact with gasoline, the flash point of the oil drops dramatically. The oil takes on a flash point closer to that of the fuel when the two come into contact. This is true in oil-injected and direct-injected 2-strokes (where the fuel meets the oil in the engine) or premix engines (where the oil meets the fuel in the gas can). You may note the term “miscibility” is often listed in 2-stroke oil specifications. This refers to the abilty of the oil mix with the gasoline and essentially become a “homogeneous solution”.
Also consider that the exhaust temperature of late model snowmobiles can be in the 1200°F range. So comparing the flash point number of 2-stroke oils in the bottle isn’t all that relevant once the oil has been mixed with gasoline and goes through the combustion process.
What To Consider When Choosing A 2-Stroke Oil
Is the ash content suitable for your application? As in, does your engine call for an API-TC “low-ash” oil or a TCW-3 “ashless oil”? Does the oil contain a high quality base oil? Does it contain a healthy dose of anti-wear additives and detergent agents? Is it suitable for use with variable exhaust power valves?
The flash point number has more pertinence for the MSDS sheet or for your snowmobile dealer’s fire insurance policy. At the end of the day, they all go out the exhaust in smoke. The more important questions are how well does the oil protect your engine and is it leaving harmful deposits behind?