Can You Mix Car Engine Oils​? Risks and Safety Tips

The check engine light comes on while you're driving down the highway, or you notice that your oil pressure gauge is falling. You pull into the nearest service station, but they don't carry the type your manufacturer specifies. You stand there, holding the conventional oil, wondering…can you mix car engine oils? We hear this story often at Arrowhead Imports. People often come to us and wonder if it's harmful to their engine if they add different types of motor oil.

Your engine’s lifeline is oil. This helps in lubrication and prevents friction and overheating. It may seem that all oils are created equal, but that’s not the case, as there can be differences in their composition from one oil bottle to another. This can lead to consequences for your vehicle’s well-being.

Can you mix oils in a car? Understanding the answer begins with recognizing the different types of oil on the market.

Understanding Engine Oil Types

To grasp why blending might be a problem, you must understand the three types of oil that are available on the shelf. Conventional oil is refined directly from crude oil and is normally used in older vehicles with simpler engines. It has a different flow rate and degrades quicker than other types of oil.

Synthetics are designed through chemical engineering to offer superior performance characteristics and protection against extreme temperatures. It resists degradation much longer compared to conventional lubricants and has improved fluidity in low temperatures. 

Next, you have synthetic blends. These offer a compromise between conventional and synthetic-based lubricants. They offer superior protection compared to conventional lubricants but cost less compared to synthetic lubricants. Each of these lubricants uses specific chemical compositions to achieve its intended function.

The Dangers of Blending Oils

Mixing car engine oil is not expected to cause an explosion or immediate failure of the engine. That being said, we strongly recommend not doing so on a regular basis. The first hazard associated with mixing engine oils is viscosity. This is the measure of how easily the oil flows. When you mix two oils with different viscosities - one thin and the other thick - the mixture may have an unpredictable viscosity that may not lubricate the parts of the engine properly.

Another issue would be the additives that come in various brands and types. These additives are added by the manufacturer in order to combat corrosion, remove engine deposits, and facilitate lubrication. If you combine various products, the additives may react in a negative manner. In some instances, they may cause the combination to destabilize. This may result in the formation of sludge in your engine or increased piston and bearing wear.

When Mixing Oils May Be Acceptable

However, there are some instances when mixing oils may be considered the “lesser of two evils.” For example, if you are stranded with little to no oil in your engine and are left with no other choice, it may be better to add it to your engine than to risk engine failure due to a lack of lubrication, which can cause your engine to seize and fail in a matter of seconds.

If you are faced with this type of emergency, you can fill 'er up and be on your way. Nonetheless, we would recommend this be a temporary solution for you. You'll want to drive carefully and get this vehicle into a professional shop such as ours as soon as possible so that a full oil change can be done and this mixed oil removed from your engine so that you are protected by the proper formula.

Protect Your Investment with Proper Maintenance

Your car is a big purchase, and taking care of it is the greatest way to protect it. Although using a combination of engine oils in a bind is a good way to get to a safe location, it is not a practice that you want to make a habit of. The dangers of oil sludge buildup are not worth the convenience.

If you are not sure which type of oil your vehicle requires or if you have recently blended various types of oil in your vehicle, do not hesitate to pay us a visit. As well as a Mini Cooper repair shop in Peoria, we can help with a range of other European vehicles at Arrowhead Imports.