On Tue, 19 Sep 2017 20:08:33 -0600, rbowman wrote:

I can't speak for chainsaws but I use 90W gear oil on both my chain
drive motorcycles and get as good a chain life as some of the fancy
spray products.

I don't know about the used oil part. The generic stuff I buy is about
$10 a quart and lasts a long time.

I normally use Lowes sticky chain lube bought by the gallon but now I have
a gallon of used 75W90 so I was just wondering ...

It must have metal flakes in it though, so it might not be worth it if it
screws up the chainsaw. I'm not so worried about the $30 chain but more
about the $350 chainsaw.