# 50:1 gas in a 40:1 chainsaw have a detrimental effect?



## wahoowad

I have a Poulan saw that requires 40:1 mix gas. It is my beater saw for odd jobs. I suspect it has bad fuel in it as it will start, rev high for 10 seconds or so then shut off. Didn't use to do this, might have started with the last batch of gas/oil I mixed up.

Due to mostly ethanol in my area I have resorted to using canned 50:1 fuel for my new Stihl MS251. I also don't go through much gas saw gas so another reason for using the canned gas. 

Anyway, I'd like to dump the gas from the Poulan and try the known good 50:1 gas unless that is a bad idea. I have abused this Poulan and not always had a perfect 40:1 mix in it but did not know how much of a difference it would make trying to run it on 50:1.


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## TreePointer

If you are using a modern 2-cycle oil designed for air cooled engines and it says 50:1 on the bottle, then you can use it at that concentration in your saws without worry.  This is true even if the owners manual for your older saws and OPE say something different like 40:1, 32:1, 20:1, etc.  The properties of 2-cycle oils have improved dramatically over the past couple decades..

The same modern oil at 40:1 is fine, too.  As always, keep your OPE properly tuned.

If you are using your saw for heavy duty activity like milling, higher concentrations of oil will help to protect your engine.


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## wahoowad

I've seen 40:1 premix for sale too. It had me wondering if there was enough of a difference that they offer both.


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## clemsonfor

I use 40:1 in everything and personally would not use any less oil than that. 50:1 is an epa thing. All of the saws and folks used 40:1 just a few years ago. 

If you have a modded saw or run it hard I would be using 32:1 per the recommendations of some of the top builders like Brad or Randy.

Less oil than that and the beating hammer themselves out and at 50:1 Randy has documented dry crank cases on failed engines. At 32:1 he has never had a failure. 

Good synthetic oil will not carbon or coke up like oldschool oils did 30 yrs ago.

Its your saw do as you wish though.


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## mark cline

I run 32 :1 in all my saws , replace the plug once a year and never had a problem. 3 of my saws are from 1980 and earlier.


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## wahoowad

I found the saw was running poorly due to a failed gas line, so my 40:1 gas was probably fine. I'll still give it a little 50:1 gas since I know it is good just to see if it runs OK after I replace the fuel line. Then switch back to my 40:1 mix for cutting.


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## clemsonfor

So many people think their poor running saw is cause the mix is not right. I can't tell a bit off difference in performance from 32:1 and 50:1. Saw runs the same. And no carburetor can tell the difference in fuel mixed 40:1 and 50:1 its just so danged close.


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## clemsonfor

mark cline said:


> I run 32 :1 in all my saws , replace the plug once a year and never had a problem. 3 of my saws are from 1980 and earlier.


That may even be a bit excessive unless you cut 20 cords a year. I just replaced the plug in my stihl 390 a yr ago due to the decompression valve coming apart and the piston slamming it into the plug pushing the gap closed on the plug. I tore the motor down pulled the parts out of the saw and reassembled it with a new valve , then replaced my plug with the bent electrode. I could of just regapped the plug and run it bit I figures it was due for a new one after 8 years.


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## mark cline

Some years I do cut up to 20 cord , just my preventative maintenance routine. Plugs are cheap along with 32:1 oil mix.


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## clemsonfor

Changing a spark plugs that often is not preventing anything, maybe a hard start or two??


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