kburns wrote:Would there be any problems with using used motor oil from my cars to lube the chain & bar on a chain saw?
Yes. your chain and bar and sprocket will all experience rapid wear - Bar oil has a "high Tack" formula to it (if you hadnt noticed, it can be quite "sticky" stuff) - used motor oil, or indeed any regular motor oil does not have that "tack" capability and slings off - it won't stay on the chain rivets (which are the bearings of the chain), it wont stay on the sprocket bearings, and won't be able to withstand the shearing - basically your end result is not much better than running bar and chain with no oil at all. Run used oil long enough, you'll start to see your bar burning blue and wearing a half moon shape into the bar rails where most of the wood gets cut - will also see uneven bar rail wear , your chain will be wobbly and "stretched" due to rivet wear.
You'll end up replacing your bar and chain 2-3 times as frequently, so I'd say the investment in the more expensive bar and chain oil formulated for the purpose is money well spent.
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)