Using Engine Oil Analysis To Determine Oil-Change Frequency
By Bruce W. Smith
One of the beauties of engine-oil analysis is that it can be used to fine-tune both the type of oil that suits an engine best and the frequency of oil changes. This can be especially helpful in the case of gas and diesel pickups towing trailers.
Lake Speed Jr. is the founder of SPEEDiagnostix, a premier oil-testing lab in Dover, Ohio, and he’s also a certified lubrication specialist and oil analyst who has recorded numerous YouTube videos related to in-depth testing of engine oils. If extending oil/filter changes is an important aspect of your RV preventive maintenance, here’s Lake’s process:
Step 1
Utilize OEM-recommended oil and do two early oil changes during the break-in process (500 to 1,000 miles and again between 3,000 and 4,000 miles). If the engine is already broken-in, skip to Step 3.
Step 2
Have used-oil samples analyzed at each oil change to establish the base trend analysis.
Step 3
Go 5,000 miles on the third oil change and take a used-oil sample. If the wear rate per 1,000 miles is below 5 parts per million (ppm), you are good. If the wear rate is between 5 ppm and 10 ppm per 1,000 miles, go another 5,000 miles on the OEM-recommended oil and resample. If the wear rate is still greater than 5 ppm per 1,000 miles, then move to Step 4.
Step 4
Review the used-oil analysis data to see if the OEM-recommended oil is falling short in any aspect (low viscosity, additive depletion, higher wear rate). If it is, try a different brand of oil that has the same viscosity as specified by the OEM. Go 3,000 to 4,000 miles on that oil, drain it, and refill with that same oil. Go another 5,000 miles and take another oil sample. See if the change in brand drops the wear rate per 1,000 miles below 5 ppm. If it does, you are good. If it does not, then move to Step 5.
Step 5
Since the change in brand did not lower the wear rate per 1,000 miles below 5 ppm, use the next higher viscosity grade of whichever oil had the lowest wear rate per 1,000 miles. If it was the non-OEM brand, resample at 5,000 miles to check the wear rate per 1,000 miles. If it was the OEM brand, you will need to use it for 3,000 to 4,000 miles to flush the non-OEM oil out of the system. Then run 5,000 miles on the higher-viscosity OEM oil to take another sample.
If either higher-viscosity oil brings the wear rate down, then stay with that viscosity grade and brand. If the wear rate per 1,000 miles is still above 5 ppm, go back to Step 4 and repeat. If the wear rate per 1,000 miles is below 5 ppm, you are good. You can then use the oil analysis results to fine-tune the oil change interval.
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Source: https://familyrvingmag.com/2025/02/26/using-engine-oil-analysis-to-determine-oil-change-frequency/
