While this appears to be a straightforward question, more than one answer may apply. Depending on what you read or whom you listen to, you might receive conflicting advice.
One side of the debate asserts that more frequent oil changes will be needed as an engine’s mileage increases, since the tolerances will not be as tight, allowing blowby and soot ingression.
The other side contends that you should be able to extend your engine oil changes because any break-in wear will have already occurred and you won’t need to worry about voiding your warranty. To say that either side is right or wrong would be a fallacy.
An engine that has been well cared for, with all the scheduled maintenance performed, should be able to support longer intervals between oil changes. As an engine is broken in, the sharp little edges and rough surfaces become polished down, enabling the surfaces to mate better and lessening the chances of metal-to-metal contact (assuming full-fluid separation at the operating temperature).
A caveat to this would be when there is wear in the cylinders and on the rings, which may allow blowby. If you know what you are looking for, a comprehensive oil analysis test slate may not be necessary. A simple blotter spot test may be enough to determine if you have fuel dilution or coolant in your motor oil.
To help you decide if your high mileage oil change intervals can be longer, consider the following advice:
If your engine burns oil or you must add oil to it at regular intervals, you should not try to extend your oil change. If you have performed a compression test on your engine and found that you are losing pressure, you should avoid extended oil change intervals. If you are not using a quality filter, you should not extend your oil change. Reconsider the filter you are using, as it will have the greatest impact on engine life. The better the oil is filtered, the longer the engine and oil will last.
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