I edited this to get the point across a little more coherent:
I was always a proponent of cheap bar oil (go read my old posts), and I still am, but, when we got the last and best modded 660 (that I have) and these modded 441's and were cutting a lot of Ash in the bottoms and swampy ground, we started to get Stihl chain stretch and burnt bars which was not happening before due to less wood being removed per second or whatever. I tried some experiements with STP and Synthetic Gear Oil and cooking oil and cheaper oil like Tractor supply/walmart/autoparts stuff, none worked with the faster saws using 28" Stihl ES bars and Stihl Semi Chisel Full Skip Chain. When running saws that were not as fast, these oils worked just fine for years, but since the faster saws, it did take the additional quality of Stihl Oil to allow for the practical use of the faster setups, without then causing multiple chain adjustments and wore out bars.
To know that it was the oil and not just the guys whining, several times I secretly switched the oil back to something cheaper than the Stihl and each time the cutters would walk back out of the woods and say something is wrong with the oil or come in for lunch and mention that they were getting the same problems, LOL. I'd tell them then that I switched it.
Also it didn't matter which oiler was on the 441's either the HO oiler or the regular one, both got hot chains with gunk stuck all over them.
I personally think that Stihl bar oil is the best, I have proven it to myself. That said, I don't think all setups need it. I know I cut for years and never thought I "needed" it, now, I know, I don't want to run slower saws just because of the bar oil, LOL.
It should be noted that I get the Stihl bar oil for $1-$1.50 more than "cheap" stuff, so its a no brainer for me. I did have thoughts of mixing it to see if the additive package in the Stihl would suffice for "fixing" the cheap stuff, but for the $1 difference, which would only be 50 cents difference per gallon after mixing, 50/50 whats the point, my time is worth something.
I still have about 10 gallons of Tractor Supply (I bought a pallet of it last year) to burn up on the saws with 20" bars on them, but should get through that this next month.
I might still check out a oil company that makes it own bar oil and will sell it for $4 per gallon if you bring your own barrel in. I bought 840 tubes of red grease from them for 80 cents a tube last year and it is great grease, so maybe the bar oil would be good to, dunno.
That is my experience with both cheap and expensive bar oil
If you don't need expensive, don't waste you money.
Sam