All car's I've had (second hand and between 15-30 years old) have always had a greasy veil over engine components.

I understand moving components need to be lubricated but this gives off the impression the components are "sweating" oil, even though no oil leak is present.

To what extent is this normal in a vehicle? Is it recommended or safe to clean this thin layer of oil off the engine? I can't say I'm 100% sure of the origin of the liquid but if does give the impression it's gunk with an oily touch, it's mostly accumulated on metallic components, mainly the engine.

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    Is this oil from the engine? Grease from moving parts? Or generic accumulated gunk from usage, environment, dust, etc? – JoErNanO May 25 '16 at 15:35
  • Edited @JoErNanO – EChan42 May 25 '16 at 15:37
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    How old are these cars? – JPhi1618 May 25 '16 at 15:46
  • Also edited @JPhi1618 – EChan42 May 25 '16 at 15:47

The simple fact is that there are tons of ways for cars to get oil on the engine rather than in the engine. There is engine oil, AC compressor oil, and power steering fluid. Over time, most engines will have some kind of leak. Maybe its a small leak from the head cover gasket or even a cracked PCV valve. It could also be spilled when filling the oil.

Most car engines are open to the road on the underside so dirty, oily water and dust will splash and blow up from underneath. Over the years very small amounts of oil and dirt just build up.

Now, combine all that with the fact that most people will never clean their engine. Unless you really care about your car, you're not going to open the hood on car wash day.

That's all a long winded way to say that its perfectly normal on an older car. However, its not ever supposed to happen. On a perfect engine, there should never be an oil leak or oil getting onto the engine (unless splashed up from the road). An oily engine means there was an oil leak or spill, and it was never cleaned. Maybe it was fixed, and maybe its a current leak.

It's totally safe to clean the oil off of the engine. "Engine De-greasers" are commonly sold at auto parts stores, and you can even find places that will do steam cleaning of the cars nether-regions.

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  • @EChan42, thanks for the check mark, but it's traditional to wait for additional answers before accepting one. Since I have the check now, someone with a potentially better answer might be dissuaded from posting an answer. You can "uncheck" and wait. Anyway, just convention. No real rules to it... – JPhi1618 May 25 '16 at 16:12

I left the oil cap off one time and went to the shop and back, then remembered. Oil everywhere, after i cleaned it it still looked like the engine was in bad shape from an oil leak or something when it was in perfect working order.

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