Originally Posted by VQrebuild96
Why is this bad ive done this and i had my mower for 9 years.. and im not filling it up with high octane i am just adding some to the gas so its basicly boosting the octane and cleaning... better then any additive.
Higher octane fuel doesn't necessarily translate to better cleaning. But what you could be doing by using high octane fuel in a small engine is contributing to air pollution. Higher octane fuel burns slower than lower octane fuel does; therefore, combustion of the fuel charge might not be totally complete before the exhaust valve opens and the unburned fuel is pushed out into the atmosphere. Lawn mowers don't have knock sensors and other electronics like cars do to adjust timing to match the fuel. Every small engine manufacturer I have seen recommends 87 octane for use in their engines.