How can I tell if my engine oil is too thick?

Usually, I bring my car in to have my engine oil changed, but I recently topped the oil up myself using oil that my husband uses for his car. I’ve noticed my fuel efficiency is worse and I wonder if it’s because of the oil I put in my car. Do you know what the symptoms of engine oil that’s too thick for my car are?

Katherine Duffy · Updated on
Reviewed by Shannon Martin, Licensed Insurance Agent.
We’re sorry you’re having issues with your car’s engine oil! Common symptoms of engine oil that’s too thick for your car are poor fuel economy, a tough time starting in cold weather, and shorter engine life.
Here’s a breakdown of each symptom so you know what to look out for:
  • Poor fuel economy: Too-thick engine oil wastes fuel because it causes friction between the engine’s pistons. This means your engine will require more fuel to do its job properly!
  • Tough time starting in cold weather: Cold weather increases oil viscosity, making it difficult for your automobile to warm the oil and flow it through the engine. This increases friction and resistance in your engine, which is why thick oil is difficult to start in cold weather.
  • Shorter engine life: Oil that’s too thick forces your engine parts to work harder than necessary. This can lead to excessive friction, incorrect oil temperatures, and incorrect oil pressure. Unnecessary wear and tear will dramatically reduce the life of your engine.
To avoid this problem, always fill your engine with the recommended oil stated in the owner’s manual.
Having the wrong engine oil can cause serious problems down the line, just like having the wrong insurance coverage could put you at risk when you least expect it.
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