Get an oil analysis before buying a used car

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Published on April 19, 2024 | 4 min read

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Side view of female mechanic checking oil of car parked outside auto repair shop

Key takeaways

An oil analysis can help you identify possible problems a used vehicle might have, like coolant leaking into its engine.
Getting an oil analysis can help you avoid purchasing a car that needs expensive repairs.
Some dealerships perform an oil analysis for free when you purchase a used car or include the costs in the purchase price.
If you’re purchasing a used car from a private dealer or dealership that doesn’t offer this service, you can purchase an oil analysis kit for less than $30.

An engine oil analysis provides insight into a variety of issues. It can identify contaminants leaking into the engine, such as antifreeze or gasoline. It can assess whether the air and oil filters are working properly. It can also determine what small metal particles have worn off the inside of the engine and whether the levels are above, below, or average for the type of engine and mileage.

If you can spot potential costly problems, you can avoid spending money on a used car that may become a sinkhole of mechanical issues.

3 reasons to get an oil analysis before buying a used car

It may not be the most common advice when shopping for a used car, but an oil analysis can be revealing. The quality of the engine can be quickly checked with an oil analysis. Your decision to buy a car should be based on a number of factors, and oil analysis can provide helpful insight into the quality of the engine.

1. Determine the engine’s condition

The primary reason to have an oil analysis done is to determine the engine’s health. An oil analysis checks for oxidation, concentration of metal particles and quality of the lubrication, among other indicators.

A previous owner should have maintained their engine and regularly gotten oil changes. If you want to know for sure, positive results from the oil analysis and well-maintained mechanic records are a good indicator that the vehicle has been well cared for.

2. Catch and prevent potential problems

Used cars, especially older models, may not have been properly maintained by previous owners. By confirming a healthy engine, you’re ensuring you are not buying a car that may not last.

And in addition to confirming the engine’s current health, you may be able to spot potential problems down the road. For example, debris in the oil could indicate corrosion or wear on your car’s components.

Even something as simple as knowing the frequency of future oil changes can help you calculate maintenance costs for the vehicle.

3. Inexpensive or free with used car purchase

Used car dealerships may offer an oil analysis as part of the purchase package — similar to getting a car history report. In this case, it may be free or worked into the administrative costs. Either way, you will get the results without having to put in any extra effort on your end.

If you’re buying a used car from a private seller or the dealer doesn’t offer it, you can purchase an oil analysis kit yourself. It may take a little longer to get the results, but it’s worth it, especially if the seller doesn’t have records of visits to the mechanic.

How to get an oil analysis done

An oil analysis can be done by a mechanic or yourself with an at-home kit. If you get it done by a mechanic, the biggest step will be waiting for it to be done and the results.

If you do it yourself, you should review the instructions on your kit and watch a few instructional videos. But here are the basic steps:

Warm up the engine and take a sample of the oil using the tubing provided with your kit.
Send the sample to a qualified laboratory.
Wait for the results — around two to three days — and review the report.

The report may include helpful comments, but if you don’t fully understand the results you can check with a mechanic for a professional opinion.

How much does an oil analysis cost?

An oil analysis kit can cost under $30, but if you get this done at a mechanic, the cost varies.

What to do if the results aren’t stellar

The choice to go through with the purchase is up to you. Every vehicle, new or used, will need maintenance. The oil analysis may reveal potential problems, but if they aren’t costly or more than you expect to spend, it could still be worth it to buy the car — especially if it meets your other requirements.

If the cost of maintenance may be too high, there is no reason you should have to go through with the purchase. Problems can snowball, and you may be stuck paying much more than the car is worth if you frequently need to take it to the mechanic.

Weigh the cost of regular maintenance against the cost of engine problems that may or may not occur. Calculate your monthly payment and consider how extra money spent on repairs could put you upside down on your loan — leading to more financial stress down the road.

Next steps

At the end of the day, an oil analysis only provides some insight into the future of the vehicle and the quality of its engine. It’s a useful diagnostic tool when you’re shopping for a used car. But it’s not the only tool, so carefully review all the mechanical and safety features of a car — as well as accident history — before committing. Also, remember to shop around with many lenders if you need financing to get the best auto loan rate for your unique situation.