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Changing/Flushing Bad Oil

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nelsongg

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A friend of mine just picked up a used boat with a 5.7 VP in it. He isn't sure when the last time the oil was changed, but he said that it looks like it has been awhile.
He wants to make sure he flushes the maximum amount of contaminants out of the engine before the winter layup. His idea is to remove the existing oil and refill it with a cheap dino oil. Run it on muffs for a while, then drain that oil. And finally, put in synthetic (which is what he plans on using here on out) before storage.

His question to me (and now to you since I wasn't sure) is it worth it to run the clean dino oil through to clean remaining contaminants in the engine? And also, if it is a bad thing to put the dino oil through the engine and then change to synthetic?

Thanks,
Greg
 
nelsongg said:
A friend of mine just picked up a used boat with a 5.7 VP in it. He isn't sure when the last time the oil was changed, but he said that it looks like it has been awhile.
He wants to make sure he flushes the maximum amount of contaminants out of the engine before the winter layup. His idea is to remove the existing oil and refill it with a cheap dino oil. Run it on muffs for a while, then drain that oil. And finally, put in synthetic (which is what he plans on using here on out) before storage.

His question to me (and now to you since I wasn't sure) is it worth it to run the clean dino oil through to clean remaining contaminants in the engine? And also, if it is a bad thing to put the dino oil through the engine and then change to synthetic?
Click to expand...
Greg, I see no reason to attempt flushing the engine oiling system...... however, the cost is minimal to do so.
I would change the oil and oil filter, and operate the engine up to operating temperature.
Look at the oil afterwards.

You don't mention what year this engine is.
Synthetic oils have been around for a while. They work well in engines that are set up with seal components designed to operate with synthetic oils.
If this engine dates back to prior to synthetic oils, you may have an issue.

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Sorry for the lack of info. I believe it is a 2003.
So basically you're saying that the amount of contaminants he will get out by running the cheap oil through would be minimal?

Greg
 
nelsongg said:
Sorry for the lack of info. I believe it is a 2003.
So basically you're saying that the amount of contaminants he will get out by running the cheap oil through would be minimal?
Click to expand...
Greg, most contaminants that are suspended in the existing oil, will mostly be removed during the oil change.
Any contaminants that may have remained, will mix with the fresh oil.

Keep in mind that this oil will not reach any bearing journals without first having gone through the new oil filter.

If concerned, operate the engine on the fresh oil, then after an hour or so, change the filter only, and add the equivalent make-up oil.
Run it again, and take another look at the oil.

If extremely concerned, take the original oil filter to a lab (one who does this), and ask them to do an oil analysis.


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