A 61 year old Poulan that still runs?? Wow! Understandably, you would be facing a dead end trying to find an owners manual for that one (though you could try writing Poulan direct - it can't hurt), but back in 1950, the majority of two-stroke engines were still using a 16 to 1 gas/oil ratio. It will smoke like crazy, but you are guaranteed that is safe, at any rate.
Poulan Pro PPBP300 40:1
.025:1, gas to oil
The fuel mixture for a Stihl chain saw is gas and oil.
Typically most poulan string trimmers are 2 cycle products. Most consumer products are mixed at 40 to 1 mixture, 3.2 oz of 2 cycle oil to 1 gallon of gas. higher end commercial product is a 50 to 1 mixture, 2.6 oz of 2 cycle oil to 1 gallon of gas.
1 oil to 40 gas.
40:1
Poulan has a diaphragm that goes bad in the carb. It's not expensive to fix it yourself if you do things like that. Take it in and it's $50.00. Plug foul out often too and simulate a fuel problem. Good luck!
From Poulan website: The fuel-oil mixture ratio for all Poulan two-cycle products is 40:1. You can obtain this ratio by mixing 3.2 oz. of oil with one gallon of regular gas. If you have other brands of equipment that require different fuel/oil ratios and you don't want to mix separate fuel cans, you should use the lowest numerical ratio. For example, if you have products requiring 40:1, 50:1, and 32:1 ratios you should use the 32:1 ratio for all products. This may cause slight smoke increase in the exhaust in the 40:1 and 50:1 products due to more oil in the fuel, but it won't damage either of the engines.
You won't go far wrong using a 40/1 mixture and adjusting if you need to.
For a 40:1 fuel-to-oil ratio, you would need 3.2 ounces of 2-cycle oil for every gallon of gas. To achieve this, simply measure out 3.2 ounces of oil and mix it with one gallon of unleaded gasoline. Make sure to shake the mixture well before use to ensure proper lubrication for your Poulan weed eater.
I've had one, but have friends with many, and all seem to use 40-1 for max power.
To calculate the partial pressure of a gas in a mixture, you multiply the total pressure of the mixture by the mole fraction of the gas. This gives you the partial pressure of that gas in the mixture.