How to Monitor Your Engine's Condition How to Monitor Your Engine's Condition With a few extra simple checks before, during, and after each flight, you can gain a broader picture of your engine's health, and increase your confidence in your aircraft. Inspect the aircraft's belly. On most aircraft, any fluid leaks from the engine compartment ends up on the belly. Fresh oil is a sign of an oil leak. Dark soot is a sign of rich engine mixture or increased combustion gas leakage past the piston rings.
Fuel dye is a sign of a fuel leak.
One quick look at the belly and you know whether there are any leaks in the engine compartment. Take your finger tip and touch the inside edge of the exhaust pipe. If your engine's mixture and oil consumption are normal, then your finger should be clean, or possibly have a slight tan ash deposit. If your finger has oily black soot, then your engine's burning too much oil. Smell inside the engine compartment for any fuel smells.