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post #1 of 7 (permalink) Old 04-09-2019, 10:40 AM Thread Starter
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Best Practices for Doing Oil Changes?


This question applies to my snow thrower but I assume would be applicable to lawnmower engines too.

My understanding is that over time, the motor oil in a small engine degrades and can have contaminants, acids, etc. that can harm the engine. My question is this: what is the best practice for doing motor-oil changes?

Is the best practice to:

(a) drain the oil and leave the oil reservoir empty until filling it at the beginning of the next usage season? (putting a notice on the machine so no one starts it before adding oil)

(b) drain the oil and immediately refill with new oil, even though the fresh oil will sit several months before being used?

(c) leave the old oil in the reservoir until time to use the machine again, and then change it?

(d) change the oil at the end of a working season and then change it again at the beginning of the next working season? (Not my favorite choice, for obvious reasons.)

Please provide a rationale for your preferred method.

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post #2 of 7 (permalink) Old 04-10-2019, 03:38 AM
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I cut tons of grass every year so I change oil in the spring then around halfway thru the season..i have always let the old oil sit in the machines till spring then change...has always worked for me ..never had an oil related problem
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post #3 of 7 (permalink) Old 04-11-2019, 01:37 AM
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I've always changed mine in the spring. I worry about it collecting water from condensation as the temperature changes during winter. Once upon a time I used to run all my stuff once or twice during the winter to let it warm up and dry out. But unfortunately don't ever get around to it anymore.

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post #4 of 7 (permalink) Old 04-11-2019, 05:15 PM
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Once a year in Spring....straight 30 HD
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post #5 of 7 (permalink) Old 04-11-2019, 06:13 PM
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Spring time. No need to replace the spark plug every year unless it gets a ton of use. Just pull it out, look it over, check the gap and go for it again. I also run a little seafoam in the gas during the last use of the season and again in the first use.
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post #6 of 7 (permalink) Old 04-14-2019, 09:43 AM
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A version of [b] is the one I like:

Change the oil [and filters] when it is hot at the end of the season, while any contaminants are in suspension, then run the engine to circulate clean oil and 'wash' all the interior surfaces. Usually no need to again change the oil in the spring UNLESS you know the engine is subject to huge swings in temperature....moisture in the oil CAN accumulate with rapid increases in ambient temperature when the engine is still cold: condensation can form inside and outside the engine. Then running an engine until hot will evaporate any water in the oil. It usually runs over 200 degrees F.

I am especially familiar with this concern from my many years of marine engine experience where the air is typically very humid. I have seen my own diesel engines dripping condensation on the outside on a suddenly warm spring day.....To avoid the worst of this, I added light bulbs for some modest heat towards the beginning of warmer weather. More recently I left heat on my boat all winter.....for equipment ashore, the equivalent would be to store it in a heated garage or inside anywhere where excessive moisture snow and rain is absent.

Every marine mechanic I know changes oil at the end of the season as I described for recreational boats not in use during the winter.

I would never leave an engine empty of oil even though I always double check oil levels before springtime starting. That seems a potential recipe for disaster: startup w/o oil.

Last edited by Robin; 04-14-2019 at 09:46 AM. Reason: added comment
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post #7 of 7 (permalink) Old 04-15-2019, 01:21 PM
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I usually change at the end of the season, just so everything is ready to go next year. Condensation could be a problem depending on how much the temp varies, but I've never had a problem.

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