Should You Check Engine Oil Hot or Cold?

How Long Does an Oil Change Take?

In the engine of your vehicle, there are two ways that you can check the engine. The first way is by looking at the light on the dashboard which will indicate when the oil is too low. The other way is by checking the oil level by using the dipstick under the bonnet. As a driver, you know how important oil is to your vehicle. Running low on oil can be detrimental to the engine and it can cause overheating – overheating means that there’s friction so the longevity of the engine will decrease.

There are moving components within the engine such as the pistons and these can stay hot for a very long time as they run against other components that cause friction. If the friction is too much, the engine can overheat. Engine oil prevents the engine from overheating because it can absorb the heat that’s created by the moving parts. The engine oil helps to moderate the temperature of the engine and reduce the amount of friction so that the engine doesn’t overheat.

Engine oil can also help to clean up debris in the engine. The main reason why the oil will get old is because it’s collected too much debris and wear dust so it can no longer perform as well as it did. Since the temperature inside the engine can get really hot, it can be a dilemma to check the engine level while it’s too hot or if you should leave it to cool down a bit.

Should You Check the Oil Hot or Cold

You should check the oil when its warm – so not too hot and not cold. Checking the oil while its warm will mean that the oil isn’t hot enough to expand and isn’t too cold enough to contract. This means that you’ll be given an accurate reading when checking the oil level.

Important: If you want to save $100s in servicing, diagnosis, and repair costs, improve your car's performance significantly and increase its value by 1.2x with little effort, download our Beginners Auto Maintenence & Repair Manual now. 

Deciding to check the oil based on the temperature also depends on the type of oil you’ve used and the temperature of your climate. The bad part about checking the oil while it’s hot is that the oil can be hot to deal with. So not only do you have to worry about the rate of expansion, but you’ll also need to make sure that the oil doesn’t burn you – the engine oil can reach temperatures of 250F so make sure that you’re careful when you touch it.

Checking the oil will ensure that you have a good quality amount of oil left to last you your journey. Driving with low oil levels or no oil levels can be detrimental to your engine so make sure to check the engine regularly. As mentioned earlier, the type of oil used will affect when you should check it since it can behave differently depending on its temperature.

Synthetic oil – if you use synthetic oil, the rate of expansion and contraction changes as the temperature changes. This means that if you check the oil while it’s too hot, you might get a false reading because it’s expanded. If you check the oil while it’s too cold, it could have contracted which means you’ll get a false reading. Checking the oil while it’s warm means that there is a limited amount of expansion, so you’ll get a more accurate reading of the oil.

Conventional oil – if you use regular conventional oil, it can also expand or contract depending on its temperature. If you do have conventional oil, make sure to check the oil while it’s warm because this will give you the most accurate reading.

Regardless of if you use a synthetic or a conventional blend of oil, checking the oil while the temperature is still cold will affect the reading. Because of contraction, the oil can contract meaning that it gets denser, so you won’t be receiving the true reading. If the engine has been out on a cold day, you should let it run for a few minutes idle so that it warms up. Or, you can check it after you’ve been driving for a while.

Tip: Make sure when you’re checking the oil that you do it on a level surface. The car shouldn’t be on a slope unless you’ll be given an incorrect oil level.

Checking Oil Level

If you’ve let the oil cool down or warm up so that you’re ready to check it, you’ll need to take a few steps. After checking it, you’ll need to decide what to do from here. You can either just check the quality of the oil or top it up of the levels are too low. If you’re going to check the oil, there are a few things you need to look out for.

When checking the oil, you should lift up the bonnet and locate the dipstick. This is usually a brighter color compared to everything else. Make sure that you take out the dipstick and wipe the end with a cloth so that you’ll receive a clear reading. Once wiped, you need to put the dipstick back into the engine and pull it out so that you’re given an accurate reading.

There’s a min and max indicator that’s marked on the dipstick. When checking the oil level, the line should be in between the min and max levels. If the line is on the minimum line, then it needs to be toped up. Make sure to fill it with high-quality engine oil (View on Amazon) and make sure not to overfill the oil when you’re topping it up.

If you want to top up the oil, there are some recommended amounts. You should use these recommendations if you’re running out of engine oil. For a 4 cylinders engine, you’ll need about 5 quarts of oil. For a 6-cylinder engine, you’ll need about 6 quarts. For an 8 cylinder, you’ll need 7-8 quarts of oil. If you pour too much oil, it can cause problems with the engine so make sure not to.

Check the Color – while you’re here, you should also check that the oil quality is good. When checking the oil quality, there are a few things you need to look out for. Over time, engine oil can deteriorate because of the amount of dust and debris it’s collecting. The color of fresh oil is a light yellow-brown color. If the oil is no longer transparent, this is a sign that you need to change the oil. The oil has turned brown because it’s been mixed with the worn-down engine dust while it’s been lubricating it. At this point, you need to change the oil to make sure high-quality oil is in the engine for it to lubricate.

Check consistency – if you’re looking for quality, you should also check the consistency of the oil. Since the oil mixes with the worn off dust from the check, it can become thick after a while. Engine oil that’s thick for the wrong reasons isn’t good – if this comes in a dark brown color, this means that the oil is bad. To check this properly, you should take some oil from the end of the dipstick and rub it between your fingers. If you can feel grit in the oil, this is a sign that there’s too much debris in there and you need to change it.

If You Don’t Check Your Oil, the Engine will Fail

If you want to ensure that your engine has longevity, you’ll need to make sure that you’re putting the right oil and doing the right checks on the engine. There’s a lot to know about oil such as the quality, additives, consistency, brand, and temperature that can all affect the way the engine runs. Failure to maintain the engine by putting in the wrong oil can cause the engine to deteriorate quickly. The key to a long-lasting engine is maintenance. Oil is just one form of engine maintenance and even this needs to be done right. Failure to main your vehicle as a whole can lead to all sorts of problems.

If you want to avoid engine problems or any other problems and save $100s of dollars that you’ll spend at the auto repair shop, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.

A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

Recommended Time to Wait

Since it’s recommended that you check the oil while it’s warm, if you’ve just been driving, you should be waiting for the engine to turn warm before you try and check it. Dealing with a hot engine can burn you and checking the oil while it’s too hot will give inaccurate readings because of expansion. The reading may should that you’ve got more oil because its expanded.

Allowing it to cool down will give you a more accurate reading. Once your engine has been running, the oil will remain hot for about 15 minutes. You should leave your oil to cool down for 15 minutes if you’re not urgent to check the temperature. If you need to check the engine oil while it’s still hot, you’ll still be able to do it, but you should be aware that you’ll receive a wrong reading.

Checking Oil while it’s warm

It’s better to check the oil while the oil is warm. If your vehicle has been out on a cold day, rather than checking the oil straight away, you should let the engine run for a few minutes. Depending on the oil that was used, it could have contracted which means that you’ll receive a false reading. Checking the oil while it’s cold can be as bad as checking It while it’s too hot. Making sure that you’ve let the engine run for a few minutes will make sure that the oil is at the right temperature for it to be checked.

Warning: Driving while the engine oil is cold can cause the engine to ware down at a faster rate. If the engine starts to work before the oil is warm enough to circulate the engine, the rate of wear on the engine is going to be a lot more. Make sure that you let the engine run when you start your car so that the oil is warm enough to start lubricating the engine.

Owners Manual

To check when you should check the oil, you can look at the owner’s manual. On some owner’s manual, the manufacturer has recommendations for when the oil is at the right temperature for it to be checked. The owner’s manual can be found in the boot or glove boxes and it’ll give you all the answers to your questions about the vehicle. If you’ve misplaced the owner’s manual, you might find it on the manufacturer’s website with a little digging.

Job Guthiri is a freelance writer with 3 years of experience writing for Motorsrun and other established automobile outlets. His focus and key interests are Tacomas and maintenance. Read our Editorial Guidlines and Fact Checking process.