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
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.
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!
You won't go far wrong using a 40/1 mixture and adjusting if you need to.
I've had one, but have friends with many, and all seem to use 40-1 for max power.
mixture
The partial pressure is the pressure exerted by just one gas in the mixture.