Ask the Expert

Question:

I had my oil changed and the shop put 5w30 oil in my car. I think that is too thin and that 10w30 would be a better choice. Can I use 10w30 oil?

Answer:

That is an excellent question. NO! The hard part is going to be explaining to you why that is my answer.

First I need to preface my response with this statement: Engine oils have become quite complex in recent years, at least as far as the ratings and specifications which the vehicle manufacturers require them to meet. To fully explore this aspect of why you need specific oil for your vehicle would be like going down the rabbit hole with Alice. I am afraid both of us would be confused by the time we were done, and I am sure you would be tired of reading!

Instead, let me explain why 5w30 is the "right" oil for your car and why 10w30 is not. (I am assuming that 5w30 is the weight that your car maker recommends)

Engine design engineers rely on the engine oil to do much more than just lubricate the inside of your motor. It is also responsible for cooling the engine and sealing the piston rings. The oil has to have certain "pumping" characteristics for it to do these jobs correctly. 5 weight oil is more easily pumped at all temperatures than a 10 weight oil. This is especially true at cold temperatures. When you start your car you need oil to immediately create the sliding friction barrier on the engines internal components and it also needs to flow through the engine at the rate the engineer determined was needed to provide the heat transfer which was part of his design.

Another reason for using the lighter weight oil is to achieve the fuel economy goal of the engine. Heavier oil requires more energy to move it around inside the motor and will actually add frictional drag to the moving parts inside the engine.

Modern machining and metallurgy have allowed manufacturers to design even tighter tolerances into automobile engines. The result for us is a vehicle that gets better fuel economy and has a much longer life span. But the other side of that equation is that there is little room for error when it comes to what oil you put in the engine. Your engine will last much longer and you will consistently get better fuel economy if you use the recommended oil.

And if you would like to jump down the rabbit hole with me and have a discussion about why the particular brand of 5w30 oil you bought for your car is not the "right" oil for your car, give me a call. But find a comfortable chair first. We might be on the phone for an extended period of time.

If you have more questions please feel free to contact me at phil@PhilsProAutoService.com

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