50:1 fuel in 40:1 machine

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1,006
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fremont nebraska
Hey guys. I got a new Stihl line trimmer (weed eater) yesterday, and got a 6 pack of their Stihl HP Ultra synthetic oil with it. Mixed with a gallon of gas, it makes a 50:1 ratio. I was wondering if the this fuel mix would be ok to use on my older Mcculloch trimmer which requires a 40:1 mix. I know this new mix has less actual oil, but wasnt sure if it being a synthetic made it far superior, and ok to use.. What are your thoughts on this guys?
 
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25,807
Location
Upstate NY
Originally Posted By: Chris142
it will be fine. the oil used is way better than what was in the past
While its true the present 2 cycle oil is better than in the 1980s, they still sell OPE (Sears for one) that calls for 40:1 and Sears sells 40:1 premix. So I am not sure if its a good idea to run 50:1 mix in a 40:1 engine. I personally buy premix and have some 40:1 and some 50:1.
 
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3,031
Wouldn't it be a little better if it were 40:1 in an application calling for 50:1? I always thought leaning toward a little more oil in the mix was better than running lean.
 
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Location
Jupiter, Florida
While 50 to 1 is just fine in lightly loaded equipment, I prefer 32 to 1 in all my equipment. Since I use the same fuel in my dirt bikes, chain saw, trimmers and blowers, it makes it easy. Plus, it's clear that highly loaded engines wear more rapidly at lean oil ratio's.
 
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14,721
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Central NY
Originally Posted By: Cujet
While 50 to 1 is just fine in lightly loaded equipment, I prefer 32 to 1 in all my equipment. Since I use the same fuel in my dirt bikes, chain saw, trimmers and blowers, it makes it easy. Plus, it's clear that highly loaded engines wear more rapidly at lean oil ratio's.
You don't have a problem with them fouling plugs? I accidentally mixed some a bit too rich (around 25:1) in the weed wacker that calls for 40:1. Keeps fouling its plug out and won't run unless it's wide open
 
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NC/SC
I make a 50:1 mix and use in everything 2 cycle. I can't keep up with them all and haven't burned one up yet. The last few years, it's tcw3 too.
 
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43,667
Location
'Stralia
Originally Posted By: Cujet
While 50 to 1 is just fine in lightly loaded equipment, I prefer 32 to 1 in all my equipment. Since I use the same fuel in my dirt bikes, chain saw, trimmers and blowers, it makes it easy.
^+1 Since reading A.G. Bell's book on two strokes (there's a new version) http://books.google.com.au/books/about/T...amp;redir_esc=y Power and life increased always when oil ratio was increased. 32:1 gives me a slightly damp exhaust, which means that the oil is making it all the way to the end of the cycle.
 

JHZR2

Staff member
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46,115
Location
New Jersey
Originally Posted By: Chris142
it will be fine. the oil used is way better than what was in the past
+1. But if it makes the OP more comfortable, Id just put the slighest splash of additional oil into the tank when filling it up. Less is more though...
 
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4,262
Location
Port Orange, Florida
Originally Posted By: Miller88
Originally Posted By: Cujet
While 50 to 1 is just fine in lightly loaded equipment, I prefer 32 to 1 in all my equipment. Since I use the same fuel in my dirt bikes, chain saw, trimmers and blowers, it makes it easy. Plus, it's clear that highly loaded engines wear more rapidly at lean oil ratio's.
You don't have a problem with them fouling plugs? I accidentally mixed some a bit too rich (around 25:1) in the weed wacker that calls for 40:1. Keeps fouling its plug out and won't run unless it's wide open
Just like they said, two stroke oil is better and two strokes don't foul plugs like before. I like 32:1 and I have had excellent results. I never go leaner than 40:1. Don't use the TCW3 oil. I have had engines tore down that the rings were frozen solid from "Boat Oil". TCW3 leaves hard carbon deposits. Two strokes are made to run wide open, don't baby them, its not a four stroke.
 

Jakegday

Thread starter
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1,006
Location
fremont nebraska
Thanks for all the input guys. I doubt ill ever put anything besides the recommended 50:1 in my new Stihl trimmer (you know what these things cost?? LOL) . But for my old trimmer, and possibly my new leaf blower which require 40:1, i think ill use the 50:1 fuel, with an extra cap full of oil in each tank on the 40:1 equipment.
 
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Location
Sweden
Don't worry, run it at 2%. That's the standard on 2 stroke premix today and unless it's a really old engine (50s-60s) without roller bearings, you will do just fine with that ratio. I do not give advice on top end go carts or road racing bikes, but I can tell you that NO ONE in the whole swedish forestry industry runs anyting other than 2% in ALL 2 stroke equipment, HVA, Stihl etc and have done so for at least 30 years. If you are worried, drop half a blob extra in the fuel but it's really a waste. I'd use my time finding a highly rated oil instead, iso egd or similar.
 
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750
Location
MN
Running more oil than the engine was factory tuned for can cause lean seizures and high engine temps resulting in melted pistons if the carb is not readjusted for the new mix. There is less "fuel" in the mix and the engine runs lean. I personally run everything on 50:1 with premium gas, a small fleet of chainsaws and blowers and various other 2-stroke equipment and have never had a failure due to lubrication problems. That is with a premium synthetic oil and the carbs are all properly adjusted.
 
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Location
Ontario , Canada
Originally Posted By: ironman_gq
Running more oil than the engine was factory tuned for can cause lean seizures and high engine temps resulting in melted pistons if the carb is not readjusted for the new mix. There is less "fuel" in the mix and the engine runs lean. I personally run everything on 50:1 with premium gas, a small fleet of chainsaws and blowers and various other 2-stroke equipment and have never had a failure due to lubrication problems. That is with a premium synthetic oil and the carbs are all properly adjusted.
^^^^^^^^^^^^^^ THIS!! I worked for Stihl Canada for 17 years . Running a good 2 cycle oil and an ethanol free premium fuel is golden .
 
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802
Location
Wisconsin
Come on!! Nobody is going to melt a piston going from 40-1 to 32-1. I dont measure the oil ratio on my 2stroke small engines, weed wacker etc. I put gas in the tank and put a couple dashes of oil in. If it revs a little slow, I put in a dash to much. Big deal. Yeah I know, not very scientific, but to say you will melt a piston is just wrong. BTW most 2 stroke engines make their best HP at 18-1 ratio. The oil helps seal the rings and you get the most compression. Though I'm to cheap to waste that much oil. Google it.
 
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43,667
Location
'Stralia
If somehow the hydrocarbon oil replaced gasoline, and escaped combustion entirely...the premise that oil leans you out and melts pistons is farcical.
 
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