Rick's Free Auto Repair Advice

Can you drive with a missing oil fill cap

It’s not safe to drive with a missing oil cap

Driving with a missing oil fill cap can be dangerous

Every engine produces blow-by; gasses that escape past the piston rings and enter the crankcase. When the oil fill cap is in place, the positive crankcase ventilation system (PCV) sucks the blowby out of the crankcase and sends it into the intake manifold to be burned. But when the oil fill cap is missing, the PCV system can’t work properly and the blow-by blows out the oil fill port.

The blowby gasses contain oil mist, fuel vapors, and exhaust. So driving with a missing oil fill cap can blow oil mist all over your engine. If enough oil blows onto your engine, it can ignite or smoke.

It’s not safe to continue driving with a missing oil fill cap

image of engine with missing oil filler cap

Driving with a missing oil fill cap can damage your engine

As you drive with a missing oil fill cap, you’re pushing oil out of the engine and that means your engine is losing oil. Running your engine when it’s low on oil causes the remaining oil to wear out more quickly, which can cause additional engine wear.

Debris can get into your engine with the oil fill cap missing

The oil fill cap helps prevent dirt, dust, and other contaminants from entering the engine. Without it, these particles can get inside the engine, potentially causing damage to critical engine components.

What to use as a temporary oil fill cap?

Do not use plastic film, tin foil or a rubber glove. Those can melt or even get sucked into the engine. Use a metal cap, like the end of a soup can. See this post for more information

Oil fill cap replacement cost

The best place to get a replacement oil fill cap is from the dealer. They always have them in stock. Plan to spend about $15-$20 for an exact replacement. However, you can also try any auto parts store like NAPA or Autozone. They may not have an exact replacement however and may offer you a “universal” cap. That works as a temporary replacement, but plan on getting the right oil fill cap for your engine.

©, 2023 Rick Muscoplat

Posted on by Rick Muscoplat

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