When Should You Get an Engine Oil Analysis?

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If you are thinking of purchasing a used vehicle–or really anything with an engine for that matter–it’s essential to know precisely what you’re buying. A standard inspection and test drive will tell you a lot, as will running a comprehensive vehicle history report and getting an inspection of the visible parts at a local mechanic.

But just as important as making sure the vehicle is in top physical condition, is making sure its circulatory system–it’s system–is functioning as well as it should be.

An engine oil analysis, like a preventative checkup for humans, can reveal potential problems well before they become serious ones and can help you stop issues before they begin. 

When Should I Get an Engine Oil Analysis? 

You should consider getting an engine oil analysis for any vehicle or piece of machinery with an engine that you’re considering purchasing. This includes anything from boats to cars and planes. It’s also a good idea to get an analysis every few months if you are already driving an older vehicle.

getting the engine of a standard car checked at regular intervals similar to an oil change every 3,000 miles, and diesel engines checked monthly.

Why Should I Get an Engine Oil Analysis?

Think of an engine oil analysis as an early warning system for your engine. By knowing if any unwanted fluids or particles are making their way into your engine, you will have a clearer picture of how well your car is running. If you do identify something amiss, you will be able to catch it and correct it well before it starts causing serious problems.

What Does an Oil Analysis Tell You?

An engine oil analysis reveals if anything is in the oil of your engine that shouldn’t be. Common culprits that can cause problems include antifreeze, dirt, or gasoline, which could leak into your engine if something isn’t working correctly, as well as small flecks of metal which may wear off the engine over time. Oil analysis also includes checking whether or not the air and oil filters are functioning correctly.

The analysis will also measure the oil’s “vital signs” just like a nurse would for a patient–including alkalinity levels, detergent levels, and additive levels. If the oil is hotter than it should be or is perhaps contaminated, those problems will also show up.

How Do I Know If the Test Results are Good or Bad?

Whether you , at a dealership, or through your city government, there will generally be a section detailing both the actual numeric results of the analysis and a section on how you should interpret those results. If you’re not sure, a reputable auto body shop will probably help you out for free–especially if it leads to more business for them.

What Should I Do with the Engine Oil Analysis Test Results?

If you are buying from a private seller and the test comes back with negative results, then you can politely decline to buy, pointing out the issues as you do so. If you are checking up on a vehicle you already own, you should speak to a trusted auto body shop and discuss what course of action to take.

What Does It Mean If the Test Reveals Metals In My Engine Oil?

Aluminum, chromium, copper, iron, or lead in your test? If a specific part of the engine is wearing down faster than it should be, you might see elevated levels of these metals; and if you do, it’s time to head to the garage for a checkup. 

What Does It Mean If the Test Reveals Dirt or Gasoline In My Engine Oil?

If this is the case, you might have an issue with your oil filtration system. It can be triggered by your fuel mixture being too rich, meaning there is too much fuel and not enough air. Have each of the following sensors checked to verify if they are working properly: 

  • Mass air flow sensor
  • Coolant temperature sensor
  • O2 sensor
  • MAP sensor
  • Intake air temperature sensor

How Much Does an Oil Analysis Cost?

Most dealerships offer this service for used vehicles at the time of purchase, as do many city municipalities. However, you can also order an online test for about $25 and send it in for analysis. It is relatively inexpensive when compared to other vehicle expenses. This is particularly helpful if you’re buying or selling a used car privately rather than through a dealership, or if you’re looking to check up on an older vehicle and don’t live near a city or an auto shop that offers the service.