Been using straight rapeseed/canola oil for nearly 8 years now or so. I work mostly in temperate climates where it rarely gets above 80*, tho. I would expect you might start to miss tackifiers once the temperatures climb higher.
Most folks bring up oxidizing issues. Straight Rapeseed doesn't seem to oxidize as much as other bio oils. It seems the glucose and the oil will gum a bit in cold climates if let to sit long enough. But I had to let a chainsaw bar sit for years(nearly 3) to get this effect where the tip became tough to pull over. It became loose the moment I swiped it across a log with a chain in it. The same saw had rapeseed oil in it's tank for the same amount of time. Once started, it flowed as well as it did when the oil was fresh. I suspect had there not been fines in the tip of the saw that it would not have gummed up so much. I have several chainsaws that can sit for a few months at a time that haven't shown any issues as far as oxidization. It shouldn't be too surprising - rapeseed oil naturally has antioxidants in it.
The bars and chains seem to last just as long. I do mostly hardwood firewood and a bit of felling. The peening and burrs don't seem to be much different from the typical bar oils I have used in the past.
To date, I have saved hundreds. Typical bar oil here is 3-5€/litre. Rapeseed oil in bulk is as cheap as .85/litre, and is the most common oil used in chippers and restaurants here. There is no tax, sales or otherwise, in Ireland on vegetable oils. VAT on mineral oils for lubrication is 23%. I haven't checked if it's got an excise tax on it as well, but I would be stunned if it didn't.
Since I mostly do my work on a private estate, nearly all of which is certified organic, the rapeseed has the added benefit of not contaminating the soil or the water for any real length of time. Our soils are tested at least once a year by the state for the certification. Rapeseed is supposed to be able to boidegrade in as little as 3 months.
I have also tried cold pressed vs standard processed. Cold pressed is around on the estate because it is used as a supplement and treatment on occasion for some of the livestock. It works fine in a chainsaw, but is an expensive version only used in a pinch - so not much usage. In bulk it is closer to 2.50€/litre.
https://www.fs.fed.us/eng/pubs/html/98511316/98511316.html
No oil stains here, and nothing potentially toxic to run off in to the lake:
That vid is 5 years old. I still have this bar as a back up. Not as purdy as it used to be, but it works fine.
