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What to Do If Motor Oil Spills on the Engine?

by Richard Rowe

Engine oil spills aren't as uncommon as you might think; in fact many engines have a certain amount of the stuff where they shouldn't. Seal and gasket leaks and accidental spills during filling happen every day, and rarely to they result in any major catastrophe.

Oil Basics

Even synthetic motor oils are mostly mineral oil by volume, which means that they operate like most other hydrocarbons when exposed to enough heat. Motor oil will burn just like gasoline or kerosene; it just burns much slower and requires higher temperatures to ignite. Generally speaking, the flashpoint for motor oil (the temperature at which it vaporizes to form an ignitable gas) falls between 390 and 400 degrees Fahrenheit; autoignition temperature (the temperature at which it will catch fire without another ignition source) for such heavy oil lands at about 750 degrees.

Consequences of a Spill

If the motor oil lands on something that exceeds its flashpoint, it'll just smoke and form an ignitable gas. However, this gas requires the presence of an open flame, and will more than likely go out if the flame does. Odds are best that the oil won't ignite unless it touches the exhaust manifold or catalytic converter, and even then there's no guarantee that those surfaces will exceed its autoignition temperature.

What to Do

If you can wipe the oil off or soak it up with a rag, then that's preferable to just letting it sit there and solidify into sludge. A little soap and dish detergent will take car of the residue, provided that you can get to it. If you can't get to the oil spill, then keep a fire extinguisher handy and start the car. Allow it to idle with the hood up and burn away the oil while you keep watch.

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