I know that there have many discussion son this topic, but wanted to contribute my experience on this one that works.
Basically on my bike 1976 CB400/4 the oil filter bolt was rock solid and I did try everything to remove which included Plus Gas, WD40, GT85, brute force, breaker bar, spanner, socket and extension, vice grips, hammer, propane blow torch etc - nothing it would not budge a mm.
My neighbour suggested using heat combined with Coca cola on the bolt especially around the flange area - the reason being is aluminium oxide is formed which is holding the bolt.
I used the blowtorch several times ( three) to heat the bolt and applied the coke with a turkey baster then just left it for two days, went into the garage today and the bolt moved quite easily - I thought I had won the lottery.
I was close to using a hacksaw to get the oil filter off but this worked and stopped any damage to the oil filter housing - hope this helps anyone else going through the same pain.