Many off the shelf bar lubes sold throughout regional NSW dealerships are bio-degradable as environmental constraints say that if one is using a chainsaw on crown lands it must be(this is what we where told when it was the old State forests of NSW, have never actually sighted the statutory personally).
Ian is right there is a tacking additive that gets less vicious as the temperature rises,thus lessening "fling", therefor the bar and chain will last HEAPS longer using the correct oil, believe me I've done the comparisons when I used to use chainsaws for a crust, and there was over 12 at any given time in the shed. on cost a 20 litre drum should be around $60, 3 dollars a litre, & most reservoirs on saws hold between .5-1 litre and you should adjust the feed to use around 1 tank of lube to 2 tanks of fuel. Overall I reckon it's a cheap investment compared to bar and chain costs.
catchy catchphrase needed here, apply in writing to the above .