So why not just use used veg oil from your local restaurant? Filter it and go. Plus its free!! Ive been wanting to do this for some time but havnt yet. It will solidify in winter but summer should be good....
Key word FREE
Don't do that. Free will cost you. Fryer oil is different than straight off the shelf grocery veggie oil, it is formulated to take high heat for sustained periods. Regular veggie (canola, cottonseed, soy, corn) is clean, inexpensive, available, non-toxic, renewable, biodegradable and friendly to the environment.
The 'bio-oils' out there have tack in them, commonly thought to enhance the performance of petroleum oil on a chainsaw bar and chain system, like it keeps the oil from flying off, or keeps it on the chain longer. This belief transferred over to vegetable based bio oil, only the stickier the oil, the more it sticks to saw parts. With oil that eventually biodegrades, you want the oil slippery, not sticky. You want deposited oil to fall off the saw, not stay stuck to it.
I really think tack is unnecessary and I'd go to the point of saying vegetable oil with tack is far worse (and more expensive) than straight vegetable oil.
I've been using straight vegetable oil in all my saws, now coming into my 5th year. The performance is great, it doesn't stink, doesn't stick all over other gear, doesn't coat your hands with toxic residue whenever you do maintenence, and you dont have to worry about cross-contaminating your family's laundry with yours.
If it didn't work well. I wouldn't endorse the idea. I have never 'rinsed' my oil tanks with anything other than fresh vegetable oil. I've never replaced an oil tank filter or any other part on a saw that I could directly attribute to store-bought veggie. Still using the same saws as years ago. Still runnin strong, thousands of tanks of veggie have been run through. If there was something wrong, I wouldn't continue, nor would I recommend a product that could harm the saw.