I have no idea where the 50:1 came from.
I have not see the owners manual etc that you would get with a newer Victa so i am not at liberty to comment on what advice they give.
What i could surmise would be that Victa were offered money by Valvoline to approve this oil, and needing money they took it.
But then perhaps the research was done, but given that it craps in the face of theory i am not convinced.
I got what i believe is a 2002 model mustang the other day. The 5HP motor with the straight inlet. The cap still has 25:1 embossed into it. The sticker on the side of the cowl that says about the fuel tap and primer still has 25:1 on it.
Untill i see a Victa with 50:1 all over it, the ratio i will use and reccomend is 25:1
I do use that same oil in my chainsaw. It was all bunnings had with that handy measuring cup built in.
The spark plugs in the later ones are a resistor plug. I do recall reading somewhere that it is something to do with the ignition, but generally a resistor plug is to reduce the electrical interference that the mower creates.
The number is the heat range and that is the same BM4A-BMPR4A CJ8-RCJ8Y The letter reffer to architecture.
