It depends on a few things.... age of saw (15-20 yrs+ older=richer), how hard the saw is going to be working (a tad richer for really big jobs), etc, but probably 50:1 will work well for you.
I gather it is an MS310 and Stihl's oil mixes at 50:1
The Stihl MS250 chainsaw requires a gas-to-oil mixture ratio of 50:1. For 5 liters of gasoline, you would need to mix in 100 milliliters of 2-stroke engine oil. This ensures optimal performance and lubrication for the chainsaw’s engine. Always use high-quality oil specifically designed for 2-stroke engines.
50:1
. What is the correct gas/oil ratio for STIHL products?A. When using STIHL branded Two Cycle Mix Oil, a 50:1 ratio (1 gallon of gasoline to 2.6 oz of STIHL 2 Cycle Oil). STIHL has Two Cycle Oil in easy to use bottles that are pre-measured for easy mixing with regular grade gasoline that has a minimum rating of 89 octane. Refer to your owner manual.
50:1 Stihl HP Ultra oil
50-1
50 to 1 2.6 oz oil to 1 gal. gas
The mixing ratio using Stihl brand oil is 50:1 or 2.6 oz. oil per gallon of gas. Stilhl oil is recommended though a name brand oil for another air-cooled equipment brand could be substituted. Most are the same ratio.
Stihl recommends using unleaded gasoline with a minimum octane rating of 89 (mid-grade) for their chainsaws. Higher octane fuels can be used, but it's unnecessary for optimal performance. It's also important to mix the gasoline with a quality two-stroke engine oil at the correct ratio specified in the user manual, typically 50:1. Always refer to your specific chainsaw model's manual for the best fuel recommendations.
I have the owners manual for my 041 farm boss it states " The mix ratio1:40 with stihl oil and 1:25 for other branded oils
Use regular Stihl 2 cycle oil. You mix it 50:1.
An oil tank for a Stihl MS310 can be bought directly from Stihl dealers. Alternatively, there are specialty shops online that sell chainsaw parts.