Should I check my oil when the engine is hot or cold?

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If you ask service professionals for their opinion on whether it is best to check engine oil when it is hot or cold, you will not get a consensus. It is not because they disagree, but it has more to do with the reason you are checking the oil in the first place. Sometimes, checking it after the engine has been operating for a while provides valuable information, but checking it when it is cool will provide other information.

This article, which emphasizes the importance of the oil change service, will shed some light on why oil is vital for your engine, how often you should check your oil, and what your oil is telling you.

Oil 101

Oil is a crucial component, often called the 'lifeblood' of your vehicle's engine. It lubricates the inner mechanical components such as pistons, crankshaft, valves, piston rods, and camshafts and soaks up contaminants that build up over time, impacting engine efficiency.

Most vehicles today use a pure synthetic or synthetic oil blend. Even if you have a classic vehicle that originally used plain old conventional 30W oil, you can upgrade to a synthetic blend. This upgrade will help extend your engine's life by reducing heat and wear and tear. Upgrading to synthetic oil will also help remove contaminants that conventional oil cannot.

In my 2003 Mazda Miata, the recommended oil is a 5W/30W synthetic blend because the engine usually runs hot, and this blend is designed to handle the heat. The main benefits of the synthetic oil is as follows:

• It provides greater engine wear protection
• It keeps the engine operating much cleaner
• It is engineered to flow quickly (coat engine components) even at low temperatures
• It protects the engine at higher operating temperatures (especially high-performance engines)
• It enables longer intervals between oil changes

When should you check your oil?

Depending on who you ask, you will get different recommendations for when the oil should be checked. In my 2003 Mazda Miata, I noticed a small leak in the oil pan and some minor leaks around the rear main seal, so I check my oil every few weeks and top it off as needed. In this situation, I check the oil cold to get an accurate reading of the oil level in the oil pan.

There are other situations when it is better to check your oil when it is warm. These include the following:

• If the oil light comes on when the engine is running but the oil level is good, it could mean that the oil pressure sensor or the oil pump is failing.
• An OBD scanner like the Innova 5610 will provide feedback on the oil level and remaining oil life.
• Check the color of your oil, which should be honey-colored on the dipstick. If it is too light or has a milky or frothy consistency, this could mean that some coolant has leaked into the oil (usually indicates a head gasket issue). On the other hand, if the oil is very dark brown or black, it is very dirty and needs to be replaced.