Hi grass,

Pretty much all the name brand synthetics are being used in OPE and LT/GT applications. Seems that whatever the owner uses and likes in their car or truck gets used in their toys. As long as the weight range and SAE classes meet the engine/ tractor manufacturer's recommendation there should be no problem.

Mobil 1 has a pretty large following in the L&G world and is readily available all over the place.

There are those that love Amsoil but it's harder to find.

My experience and what I've read encourages engine break-in with dino oil and then changeover to synthetic between 50 and 100 hours unless the engine comes from the factory with synthetic in it.

One caveat... if you've got an older engine with lots of hours on it there are conflicting reports from people who have changed over to synthetic as to their satisfaction.

Thanks JAL

So, would you recomend 10w-30, 10w-40 or 20w-50? What do you use?
It's a 1996 Onan. I put in 10w-30 last fall for winter ploweing (3x) and thought I'd leave it in for the summer, but now I'm getting a bit of noise (closest I can discribe it is knocking).

I wouldn't switch an old Onan to synthetic. A lot of the guys that own older 3xx series JDs with Onans keep then on dino oil. Maybe they just don't want to take a chance with Onan parts getting harder to find and how expensive Onan parts can be.

When I was a young pup an old timer told me "there's no such thing as engine overhaul in a can" and there still ain't.

If your Onan is knocking then changing to synthetic won't make that noise go away. Only money, a machine shop, and the parts department will make that noise go away.

I used to drive a VW Fox 140 miles per day, to a distant job site, and when the engine got a bit noisy, I tried using 50W mineral oil, available at a local auto parts store. That engine quieted right down, and ran fine, for many thousands of miles. But you could only use this oil when the temperature remained above 60 degrees F. It had to come out in the fall, or the engine could not be started.
Unless you wanted to put a heat source under the sump, and warm the oil for an hour or so.

The noise you are hearing on that Onan could very well be piston skirt slap. That in itself is more an indicator of an engine with some degree of wear, but can also tend to be a factor from high ambient operating temperatures also.
So make sure that you aren't collecting any debris or other stuff that hampers cooling air flow through the engine shrouding.
You can try 20 W 40 to see if it quiets the noise.
Piston skirt slap is basically the sideways reaction movement of the piston that happens when the crankshaft rod journal shifts its orientation from one side of the piston to the opposite side during a revolution (turn of the crankshaft).
Thin oil, or "thinned oil" due to heat, does not offer a substantial film of coverage to "cushion" or dampen the impact noise of piston skirt slap. Air cooled engines are more likely to push oils to their upper temperature limitations than liquid cooled engines because "normal" operating temps of air cooled engines might run 250 degrees F or hotter.

Best bet is to go to the engine manufactures home page and see what THEY recommend you use in your engine.

Walt Conner

Thanks for all the replies.
Thanks for the technical input (This isn't the usual knock sound, it very well may be skirt slap), mownie and I do keep the engine clean--blow it off after every mow and I do a 15 min cool down.

Bill, the manufacturer's recommendation is what percipitated the post.

I bought this tractor mainly for snow plowing (age and bad knees nad acute laziness). It's way more machine than I need for mowing, but does a nice job of it.
I put about 50-65 hrs a year on it and quite a bit of that is warm up and cool down. Right after I bought it we started getting these mild winters--only plowed 3x last winter.

My issue is 2 fold. One I like synthetics as I think they can extend engine life. 2. I hate to throw out oil (or store it for a year) after just three hours of use-plus change the filter with the oil change (10w-30 winter oil), so I was looking for an oil that I could keep in it for the full year. As I said, the current 10w-30 seems to not give the summer protection needed and I can't find synthetic 30w even if I started changing oil for summer and winter. So I was wondering if a 20w-50 would give me year around protection. We do get 90 day temps here in NE ohio but my mow only takes 35 min.

Here is the manufacturer's recs:
32ð F (0ð C) and higher.................SAE 30
0ð F to 80ð F (-18ð C to 27ð C)........SAE 10W30
or SAE 10W40
-20ð F to 50ð F (-28ð C to 10ð C)....SAE 5W-30

Thanks for your time, expertise and ideas guys

I personally would not have a problem running 20 W 40 or 10 W 40 in an engine that had accumulated 1,000 hours (or more).
I would not recommend using any oil that has a "50" in the designation.

Thanks guys,
I guess I may just go back to a 10w-30 dino for winter and a 30 or 40w dino for summer. I just wish oil changes on this tractor were easier--but that's for another thread.

You can always get one of these pumps and change the oil through the dipstick tube.

http://www.liquivac.com/applications/small-engine-oil-change/