Skip to Content

Is It Safe To Drive Without An Oil Cap? | What To Know

One of the most frequent maintenance requirements every driver faces is refilling and changing the engine oil. Having an oil change business leave the cap off is rare, but it does happen. I have worked as an insurance adjuster for over 20 years and have seen the result of this type of neglect.

Driving without an oil cap is unsafe for your vehicle and can quickly lead to irrevocable engine damage. Without a seal, the oil can leak into the engine compartment. Due to a lack of lubrication, your engine may overheat. This can cause it to seize, requiring engine replacement.

A replacement oil cap is usually very cheap. Here is a universal cap found on Amazon. It’s not worth the risk so make sure you pick up a replacement asap.

Oil changes are routine maintenance for all vehicles, and forgetting to put the oil cap on can happen to even experienced mechanics during the process. It’s good to know the warning signs indicating that your oil cap is missing, and how to deal with your car if you discover you’ve been driving without one.

Risks of Driving Without An Oil Cap

Close-up of a car engine with oil stains filling hole

Regardless of why you don’t have an oil cap, your engine will be adversely affected if you don’t cover it soon. There are several things that can lead to engine problems that can be expensive to correct, or in the worst-case scenario, catastrophic for your engine.


Without an oil cap, your oil supply is open to the air. Alas, roadways are not clean, and all the debris on the road’s surfaces can find its way into the oil. Granted, every car has an oil filter that will protect your engine for a time, but eventually, it will clog with the extra debris. The particles in the oil will start to lodge into the engine parts and generate friction, resulting in wear and tear as well as heat. You will likely hear knocking noises as an indication of this, and if this is happening, then your engine rods are going to loosen. Due to these side effects, an innocuous bit of dust can cause a lot of damage.

Oil Leakage

Without a cap in place, it is easy for oil to leak from the top of the reservoir, especially when you are navigating through roads filled with potholes or speed bumps. While oil leakage presents its own cleanup problem, the main concern is low levels of oil for your engine to use. Small volumes of oil will result in a lack of lubrication of the engine, resulting in increased wear and tear. Further, oil is needed to clean your engine and remove heat from engine parts that are not regulated by the radiator coolant. Sufficient oil is also required to maintain adequate engine power and protect your engine from corrosion.

Related Is It Safe to Drive Without an Exhaust Pipe?

How Do I Know If My Car Is Low On Oil?

The first indication you will probably have that your car is low on oil and needs a top-off or a change, is that the warning light will come on in your vehicle. Take note of this, as running your car with insufficient oil is bad for the engine and will lead to severe mechanical issues.

If you have an older model of car, get into the routine of performing the dipstick test, as this will keep you apprised of the current oil volume. There are a few things that your car will do to indicate that your oil level is low. Low oil volume will mean your engine components aren’t being lubricated sufficiently, creating undesirable engine noises as the components rub against each other.

Of course, all this friction creates heat, and it will make your oil smell as though it is burning. The final thing your car will do is suffer complete engine failure. There is no way to fix this issue; the engine will need to be replaced, so don’t ignore the earlier warning signs.

Can You Add New Oil To Old Oil?

If you use the same weight and type of oil, you can easily top off your old oil with some new oil. In fact, when you do an oil change, you will never entirely remove all of the oil before adding in the new, clean oil. Therefore, your oils will always mix. However, if your oil is requiring changing, which you can tell by the oil no longer being a clear golden color, do not just top off the oil. It is best to change the oil completely.

Vacuum Leaks

The oil cap also helps regulate the pressure inside of the engine as it brings the oil through it. While driving without an oil cap, you may notice that the engine feels as though it is ‘coughing”. That is, a slight jolt with a rattle while driving. In the short term, this won’t do any damage, but for an extended period, this will result in expensive repairs.

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

Engine Oil Cap Left Off

Chances are, your engine will jolt a little while driving without an oil cap, giving you a chance of early intervention. If it doesn’t, you may notice some oil spilled on your driveway, or a light indicating that your engine is running hot or your oil level is low. Don’t despair if you find that your oil cap is missing. It doesn’t necessarily mean that your engine is permanently damaged if you caught the issue early enough. There are three things you should do immediately to circumvent any issues this mishap may have caused.

  1. Put the cap back on
    This may seem obvious, but if you changed your oil yourself, then chances are it’s lying around in your garage somewhere. Before cleaning anything, put the cap back on. If you had your oil changed elsewhere, then order a new cap before taking your car anywhere else. Most after-market oil caps are universal, and you can use a plastic or metallic one. Just make sure it fits your vehicle and you’ll be good to go. This will prevent further contamination or oil loss while you drive your car to a mechanic for an oil change.
  2. Get an oil change
    Unless it has only been a few miles of driving without an oil cap, it is best to get an oil change. Minimally, you should top off your oil to replace any fluid that has spilled. Changing the oil will remove any particles that have entered your reservoir, avoiding the opportunity of engine damage via friction. If you live up a dirt track, or a stone road, i.e., anything without a finished surface, this is especially recommended.
  3. Change your oil filter
    Your oil filter is there to remove most particles from your oil before it enters the engine to prevent damage. However, it’s capacity is limited, and it is likely that it has become full while driving without an oil cap. A new filter will help clean your engine too of any debris that wasn’t removed during the oil change. You can change the oil filter on its own, without changing the oil. However, if you think your filter needs changing, don’t skip the expense of an oil change. Always better to be overly cautious than run the risk of not preventing damage.
  4. Clean up the mess
    Do clean up an oil spill as soon as you can. It won’t damage your engine, but it is a flammable substance once it reaches 150 °C, as that is when enough vapors are given off that it can ignite. Consequently, spilled motor oil is always increasing the risk of fire. The best methods to absorb oil is to sprinkle either sawdust, cat litter, cornstarch, or a commercial product for absorbing motor oil. Let the substance fully absorb the oil and then wipe it away.

Final Thoughts

Regular maintenance is required to keep a vehicle running optimally. For example, the correct air pressure in your tires increases fuel efficiency and safety, the topped-off coolant protects the part of the engine from overheating, and clean filters in your car are required to optimize the combustion process.

Driving without an oil cap can lead to permanent and potentially irrevocable damage to your engine if it remains in this state long enough. Two major issues will occur; contamination and fluid loss.

Foreign objects in your oil, such as dust, leaves, or small stones, can destroy the internal components of your engine through friction and clogging. Low oil levels can lead to the engine overheating, working inefficiently, or its internal parts not being lubricated adequately.

If you discover that you’ve been driving without an oil cap, replace it as soon as possible before topping off the oil or getting an oil change. If needed, also replace your oil filter to keep your engine working optimally.

And, don’t forget to carry a fully stocked car emergency kit for the event of a breakdown! Thanks for reading.

Related Questions

What’s The Difference Between Oil Types?

There are four main types of motor oil available. These are fully synthetic, synthetic blend, conventional, and high mileage motor oil. Which you opt for depends on your climate, driving habits, your vehicle, and its age.

  • Full synthetic is best for engines that are concerned with peak performance and want the best lubrication. This type of oil is resistant to thermal breakdown and the build-up of oil sludge. It is the most expensive oil you can purchase and, although the best, may not be necessary for every driver.
  • Synthetic blend oils use both synthetic and conventional oil to make a mixture that can give some of the benefits of full synthetic for half the cost. Increasingly, users opt for this as it a good middle ground in quality, and it makes switching to full synthetic or conventional oil easier.
  • Conventional oil is the most commonly used and is best for low-mileage, new cars.
  • High mileage oil is for vehicles that have more than 75,000 miles on the clock. This oil is designed to reduce oil consumption, smoke, and emissions that are typical of older engines.

For more, don’t miss What Should I Do if My Car Runs Out of Oil? | Get Answers.