Can you really do harm leaving last season's oil in through winter?

[aigram]

I did not drain and replace the oil in my FJ, like I normally do for winterization. Couple of reasons:
I plan on doing a clutch job before the start of the 2022 riding season
Life got in the way, and now it's consistently below freezing in my workspace.

I've read that used motor oil can over time cause corrosion inside a crankcase. In this case though, we're only talking about 5 months, and oil that easily has less than 2k miles on it. On top of being the quality Motul oil that RPM sells.
Do I need to change my oil regardless, or am I safe to wait to do it just before riding season starts here in Wisconsin?

[fj1289]

Personally I think you are fine to wait to change the oil.  I would definitely change it before running the bike, but I think you are OK to wait.   Is it "best" to do it before the layup - sure.   Are you going to permanently damage anything this year because you didn't - highly doubtful! 

I do know oil acidity is something that gets checked if an aircraft engine has set for some time without being properly prepared f or storage and has not been periodically run in the mean time.   I also know we had some engines in Colorado that were not properly stored and the oil acid levels were fine after more than a year.  If it had been in a humid location like Florida the results would have likely come back bad.   Humidity is a larger factor in this. 

I wouldn't lose sleep over it!

[Ted Schefelbein]

I think you are fine, Alex. I have been storing cars and motorcycles for about 40 years over the long winter here in Minnesota, and changing it in the spring, after I light the engine and warm everything up. Never have had a problem. I do remove ALL the fuel for winter storage, I figure if it isn't there it can't cause me problems. My brother and a few buddies fill the fuel to the top, and add Stable additive, no problems there, either, but, I figure 6 month old fuel is not in my best interest.

Ted

[aigram]

Thank you for the insight! I appreciate that the Midwest winter folks chimed in on winter storage
Re: fuel over winter, I go back and forth on this one. This year I'm going the route of add Stabil and fill to the top with 93 no ethanol. If I could store my bike in a more temperature controlled environment, I would likely drain it, but alas.

[FJmonkey]

From a chemical reaction perspective you have the cold on your side. Unless the reaction generates its own heat, the cold just slows all the reactions down. Having been on the west side of the USA I have not had to winterize anything. Well, maybe my wardrobe, break out the heated vest and toss out the worthless anti-fog and hope to find a good one (no pinlock options for me). I almost forgot, lubricate the gimble bearings on my cappuccino cup holder... 

[5speed]

I've been leaving the oil in my 86 camaro over the winter if it wasn't due for a change before I put it away.
My thought process is..all the oil and gunk will be in the oil pan and if I change it before firing it up for the first time I will get rid of most of it.
Knock on wood in 18 years it hasn't failed me yet.
I'm doing the same with the bikes.