Oil mix ratio

[mattallica]

I know this got beat to death on AS .....but I see no posts on it here.
My question is....I have multiple saw sizes and brands...all supposedly calling for a different ratio.
for instance my Partner says...'50:1 with Partner oil...all others 25:1'
In my dirt biking experience I was taught that in a 125 mx...you should run it around 40:1...and in a 250mx..you could go 50:1 and be safe for most any style of riding.
the logic behind it being that a 125 tends to run at much higher rpms consistently and benefits from the added lubrication.

which leads me to my question...I think....based on the use of a good quality synthetic oil...shouldn't one ratio...say around 45:1 or so be fairly universal...or is it more important in air cooled engines to be spot on with the factory recommendations?
I was always told that the factory set them up 'rich' on the safe side and that there was room to play.

[MCS]

Many years ago, probably when your grandpa was a kid, 16:1 mix of 30 weight non-detergent oil was pretty much the standard for 2 cycle engines. That is/was oil used in 4 cycle engines that didn't have a pressurize system and oil filter. Detergents in motor oil help clean but also suspend "dirt" in the oil so the filter can get it.
Oil specifically designed for the 2 cycle engine showed probably in the '60s but it was still 16:1. As the oil designed for 2 cycles improved, the ratio was reduced and now a lot of it is 100:1. The design of the two cycle engine hasn't changed that much but with the improved oils, Homelite released 32:1 oil in the early '70s. Now, I use oil rated at up to 100:1 mixing and mix it 50:1 but that is my choice.
Burning the old 30 weight oil left a lot of carbon in the exhaust port and I've chiseled out a lot of it, but I don't see that much any more with modern oils for 2 cycle use.
One thing to remember on two cycle engines, a lean high speed fuel adjustment also means a lean oil supply for the engine. When I adjust the high speed needle, I make sure I have a slight miss at full RPM by opening the needle.

[mattallica]

interesting info....makes total sense.
would a good synthetic that I typically use in my 250MX bke be just as safe??
would seem to be to me.

[MCS]

I would think so because your MX bike is air cooled just like a saw. By the way, keep the saw cool by frequent cleaning of the air passages around the cylinder. 2 cycle oil rated TCW is Two Cycle Water and I think it is designed for outboards or at least rated for them. They probably run a little cooler that fan cooled 2 cycles. I have two snowmobiles that have variable exhaust and they require an oil designated as VES ready. I'm will start using that in my saws soon.

[quiverpup]

heres my 2-cents.Long version.I'm running a 1956 Johnson 15 hp outboard for fishing.Runs great.They called for 25:1 back then.It's not clogged up with carbon,not worn out.My old homelites are all fine with nice looking cylinders.32:1.I have an old Hoffco weedwiggler,runs great. Calls for 24:1.I think all that extra oil helped to keep these from wearing real bad.I run good tcw3 oil in everything at 34:1.Stuff may smoke a bit but i think i'm getting plenty of oil.50:1 makes me nervous in oldies.When i ran my 292 yamaha in vintage snowmobile racing i played around with amsoil. used the 100:1 mix at 80:1. I would run a fresh engine with mineral oil till it was broke in then switch.They only lasted a season on average.This was in stock class with stock motors.They are about bulletproof motors good for thousands of miles yet i would lose the crank bearings on them and pistons were scuffed up bad.after a few of them i started using that cheap Castrol snow oil,the stuff every corner store sells up here.Steady diet of that and no more cooked motors.You cant make hp with oil but they last longer!Anyway,thats my take on oil mixing.Give em plenty and they will last another 30,40,50 years.As a side note,the hot "mix" for race sleds in the late 60's early 70's was reportedly 20wt. oil mixed with white gas(coleman fuel).Holy crap,i would not put that in anything!!!!

[mattallica]

good info guys...I'm lovin it!1

I suppose my next question is....why does the Partner say to use 50:1 partner oil...all others 25:1...seems a bit extreme....was partner oil a synthetic perhaps?

[daustin97222]

I have always over-oiled my two-stroke engines, even going back to my first 1966 Suzuki. Knock on wood: I have yet to sieze one up or throw a bearing. I would rather clean a plug and a port than fix a lower end. But it is a preference, and my neighbors probably don't appreciate the smoke and noise coming out of my old Homelites. But I've owned a garage full of two-stroke stuff from various vendors and no siezes in 36 years.

I use a top-quality synthetic blend and I mix it 25:1 (2 x 50:1 or half the gas). One caveat: I am nervous about varnish in the carbs so every winter I run them all of the way dry. All of the older Homelite saws that I have point to 16:1 so 25:1 might be a bit lean (I have little experience with the older Homelites but I am learning from you guys).

I would rather run them wet and worry less. That's just my opinion and I am no expert.

[MCS]

I found a couple of articles quite informative on the subject of 2 cycle oil.
www.sea-doo.net/techarticles/oil/oil.htm
snowmobile.off-road.com/snowmobile/article/articleDetail.jsp?id=253908

[rowdy235]

I'm sure some will argue with me, But I run in all my air-cooled 2-strokes a good quality oil at a 50:1 mix. Weedwacker, Chainsaw, etc.

[mattallica]

no argument here...sounds like basically what I plan on doing...I'll probably use the Super M that I run in my CR250...Just cuz I like the smell!!!