Car Doctor Q & A: Can the Wrong Oil Cause My Car to Run Poorly?

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This week, John Paul fields a question that everybody who has ever spent any time working on cars has been asked at least 100 times, and which hardly ever results in a satisfying answer. Except for this time:

Q.I had the oil changed in my truck (it’s a Hemi) by the local quick oil change place and all was fine for a few days. After about 300 miles the check engine light came on and the car just wasn’t running correctly. I went to the dealer and they told me it was because of the oil change and the type of oil they used. The dealer flushed out the old oil and added new oil and all is fine. I remember way back when my car used 10-30 oil and I always used 20-50 oil and had no problems. Are car engines really that sensitive to oil type?

A.Yes, on today’s cars it is very important to use the correct grade and type of oil. There are several technical service bulletins from Chrysler that in multi displacement engines that it is critical that the correct grade is used. Failure to use the correct oil can result is drivability problems as well as illumination of the check engine light. My suggestion with any modern engine is to use the oil recommended by the vehicle manufacturer.

(Editor’s Note: there’s a symbol on each and every quart of oil sold in the United States. Read the guide below. It contains all the information you need to know about that particular oil. Match it up with what the owner’s manual suggests.)


John Paul is public affairs manager for AAA Southern New England. A certified mechanic, Paul tests dozens of new cars each year and also hosts a radio show on AM 950 and 550.

John Paul

John Paul


  1. I had a hand-me-down Toyota. It got me wherever I needed to go (withing the city), but I never wanted to check the oil on the vehicle. After some time, I killed the car for lack of oil on my part. I’ve learned my lesson, but I’ve also learned from your answer that the correct grade and type have to be used when dealing with oil. I’ll have to look at my manual for this.

    1. Check the oil and other vital fluids at least once per month more often on an older car and top up or change as needed. When in doubt check the car owner’s manual or factory website.

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