So, for whatever reason, you forgot to put the oil cap on your engine and wonder whether it will affect its performance. The oil cap is used to close the hole in the engine tank, preventing oil from splashing out of the engine. 

In this article, We’ll look at what will happen if you don’t put the oil cap back. We will also review some solutions in case you misplaced or forgot to replace the oil cap.

What happens if I drive my car without the oil cap?

The oil filler cap is near or on the valve cover. This cap covers the hole of the oil tank, which is needed when checking the engine oil level or refilling the oil. The oil cap properly seals the oil tank, preventing oil from escaping. 

If the oil cap is not installed correctly, the engine may experience the following problems:

Clogged Engine Oil

Impurities from the outside, such as dirt and debris, can enter the oil tank. This external impurity then combines with engine oil, limiting its flow.

As a result of the oil not flowing properly in the engine, you may notice friction and overheating. If you notice that the oil is overly clogged, it is useless now. Make sure to have it drained before reinstalling the oil filler cap. Clogged engine oil can also result in the air coming out of the cap.

Vacuum leak

The absence of an oil cap can cause a vacuum leak in the engine. This is because the PCV system draws more air from the breather cap to the intake manifold.

The engine may make hissing noises as a result of the vacuum leak. Moreover, a vacuum leak can cause the engine to lose power.

Oil Spilling 

If there is no oil cap, oil can spill out of the oil tank through the hole while driving. 

Because of the cap’s location, some truck models can run without oil spilling. This is if you drive on a plain road and your speed is less. But for most modern vehicles, oil in the tank will spill all over the engine if you drive without the oil cap.

This will cause oil patches to appear all over the engine. Oil spilled over hot engine parts can also cause a burning oil smell throughout the engine. You may also notice a low oil pressure or low oil level warning on your dashboard.

What should I do if I lose my oil cap?

Most likely, you forgot to reinstall after opening the oil cap and refilling the oil, and you’re now stranded far from home or the nearest gas station. 

In that case, let us look at some temporary alternatives to the oil cap you can try. At least this will work until you get to a location where you can find the oil cap.

Apply duct tape

  1. Clean the area around the oil fill hole. 
  2. Place 2 inches of tape on the hole.
  3. Press the tape to ensure proper sealing by pressing it with your finger.
  4. Wrap another 2 inches of tape over the first layer, slightly tilting the direction.
  5. Press the tape again with your fingers to ensure it is properly sealed internally.

Using a Rag and a Rubber

  1. Clean the area around the oil fill hole.
  2. Place the clean rag on the hole.
  3. Properly tighten it with rubber to ensure no oil leaks.

What to Do After Discovering You’ve Been Driving Without An Oil Cap?

So you’ve discovered that you were driving the car without an oil cap. You will replace the oil cap and resume driving. But no, here are some things to consider if the oil cap has been missing from the engine for an extended period.

  1. Use a degreaser to clean the oil spilled in your engine.
  2. Remove the old oil. Without an oil cap, the oil is likely to become completely clogged, resulting in improper engine lubrication.
  3. Inspect the oil filter; it may have become too jammed due to preventing external impurities from entering the oil. If it is severely clogged, have it cleaned or replaced.

FAQ’s on Driving Without Oil Cap

The price of a new oil cap is determined by the quality and brand of the cap. A new engine oil cap can range in price from $10 to $50. Plastic oil caps are typically the least expensive and most widely used on the market. Aluminum and steel oil caps are more expensive and durable than plastic.


To summarize, the oil cap is an essential component of the engine. It properly seals the oil tank, preventing external dirt from entering the oil and oil from escaping from the engine. So, after removing the cap, make sure to reinstall it properly.

Do not  Drive your car without an oil cap or, at the very least, seal the oil filler hole with some duct tape. If you’ve lost your oil cap, get it ordered as soon as possible.

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