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1990 Yamaha Big Bear 350 - Engine Oil Questions

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Hi All,

I will start by saying I am real new to ATV's but not to wrenching. I just completed a complete fluid change on my 1990 Big bear 350.

The owners manual recommends 20w40 for the engine oil but I see nearly everywhere people using 10w30 or 10w40.

I actually was unable to find 20w40 so I used 20w50 that I did find at Walmart.

My questions are:

1) What is the Statndard that is OK?

2) Is regular oil for Automobile OK to use?

3) Whats the difference in Auto oil vs Motorcycle oil vs ATV oil? Is there any?

Thanks!

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you have to use atv oil, there are additives in the oil for the transmission. 10 40 is about standard. i would go to synthetic myself, doesn't take much to fill the crankcase, so it isn't as expensive as a car oil change. you could even go 5 40 or 0 40. the lower the first #, the easier it is to crank over. the higher the second #, the heavier it is. 0-5 40 would be good in cold climates, and 40 weight is about standard ...

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if you put car oil in, you jepordize the clutch. just saw your last post. car oil will be ok for the engine part of it, but may give you a false reading that the clutch slips etc...

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Thanks for the info!

Let me follow up with this one building on my other post. In a nutshell, due to the amount of shavings found in the oil filter on the oil change I just did, I fully expected to do another oil change after running for a few miles just to validate a clean engine.

Do I risk any damage running for a short period with the 20w50 I have in there now?

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you will only risk the clutch, but it really shouldn't do damage, it just won't help it ...

that's just if you're putting around and not working it hard ...

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thanks again!

not really working it since it has been unused for so long I've been mainly giving the kids rides around the yard so far.

This weekend I'll get the proper ATV oil and run thru another change.

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