Even current manufacturers still specify a range of different mixes from 25:1 to 40:1 and 50:1 AVB and it is mostly to do with metals used. Naturally if using a particularly good oil you can get away with different mixes but even with the I would still mix for mid range rather than run a 25:1 engine on a 50:1 mix especially on a chainsaw used on hard Aussie eucalyptus varieties such as Ironbark.
It kinda strange how different parts of the world is doing things differently. Here all 2C is now 50:1; although, some users that use larger chainsaws in milling applications are preferring to use 40:1 mix. We still have older equipment that would require special mixes if using standard fuel oils.
So far the biggest problem have I cutting any wood here is keeping a correctly sharpen chain. I get customer's chain that look like were used to cut rocks. As for extremely hard wood and stone it is recommended to used carbide tip chain. The carbide is what a lot of the rescue personnel use when they need a saw to cut about anything in an emergency or go with gas powered circular saws. Both saws have their place in rescues.
Now NormK it not that hard figure the amount of need oil but it does takes a little math as I think your gallons and pints are imperial where ours is US so amount per gallon of fuel oil would be slightly different. Gallons would need to converted to ounces and liters to milliliters or centiliters depending what you have to measure with.
