Changing/Flushing Bad Oil

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nelsongg

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Jun 20, 2006
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21883
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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
 
What year is the engine? How many engine hours? Is it fuel injected? Does he know what kind of oil is in the engine presently? Synthetic oil has more detergent action than dino oil so if it already is using synthetic oil, flushing is not necessary. If the engine is older than 1998 and is not fuel injected then what he is proposing is fine. Only change would be to run the dino oil until it's hot and then add a quart of "engine flush" (usually kerosene) and idle the engine for an additional 5 minutes. Then drain and refill with synthetic (if recommended by the manufacturer). If he cannot drain the oil completely (uses suction through the dipstick) then don't add engine flush as it's complete removal is necessary. Personally, I don't think flushing the engine with oil is worth it, or necessary. Running the engine until hot, draining and refilling with the correct oil is probably just fine.
 
My advice would be to skip the flush job. After a few regular oil changes using synthetic oil the engine will be much cleaner.
 
quote:
Originally posted by Neverending

What year is the engine? How many engine hours? Is it fuel injected? Does he know what kind of oil is in the engine presently? Synthetic oil has more detergent action than dino oil so if it already is using synthetic oil, flushing is not necessary. If the engine is older than 1998 and is not fuel injected then what he is proposing is fine. Only change would be to run the dino oil until it's hot and then add a quart of "engine flush" (usually kerosene) and idle the engine for an additional 5 minutes. Then drain and refill with synthetic (if recommended by the manufacturer). If he cannot drain the oil completely (uses suction through the dipstick) then don't add engine flush as it's complete removal is necessary. Personally, I don't think flushing the engine with oil is worth it, or necessary. Running the engine until hot, draining and refilling with the correct oil is probably just fine.

Click to expand...


Sorry for the lack of info.
It's a 2003 VP 5.7Gi-B. No idea how many hours are on it, but it looks fairly clean. Yes, it is fuel injected. I'm not sure if he knows what kind of oil (is there a way to know if an oil is dino or synthetic) is presently in it. If he can't determine what kind of oil is in it, would it be detrimental to his engine to use the engine flush with the dino oil if he decides to go that route?

Greg
 
nothing wrong with the cheap oil flush however he wont burn out any water etc in the engine because the oil wont get hot enough on muffs. S cheap oil for layup run it loaded in spring then do the final oil change is the best route to his objectives. Or just do what Rat said.
 
Thanks all who replied. I will pass on all the info and let him make a decision on how he wants to proceed.

Greg
 
I would not put the synthetic in until spring. Flush and fill with dino for the winter. I don't know if synthetic loses any properties over time like dino does.
 
Todays detergent oils have very good cleaning action. Dirty looking oil comes from the combustion of gas. Unless something very wrong was done like no maintenance at all. Probably very little wear was done to the engine.

I prefer seeing a boat for sale with old oil cuz it tells you a lot about the engine. Fresh oil tells you nothing...and may be hiding something.

Drain a couple Ozs of oil and look at it. Feel it for metal particles. You can send it in for analysis but I bet you just find dirty looking oil.

You can flush it to make the oil look clean but there shouldn't be enuff left in the engine to cause a problem. The only places that may hold oil besides the pan would be the lifters. There could be a couple OZs there.

Just change to synthetic before you winterize, if you plan to anyway.
 
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