1978 Johnson 85hp Javelin Sea horse

1st pls what spart plug do i nead to use for my motor
2nd Using high octane fuel for my engine makes a difference ? and wy
3dr ok famus question oil ratio 5 galon of gas for how many = oil ? let put that more dificult canadian liter // 20L for how many oil
4th tel me the best oil i nead to use for my 2 stroke
REGARD
SAM
MONTRÉAL,QUEBEC
:?:

 

spark plug champion L77JC4.
yes on high octane unless low compression head gaskets are install because this engine was designed for 92 and predetonationcan be likely.
50:1 fuel to oil ratio this is 16oz oil to 6 gallons of gas or 475mL of oil to 22.75L of gas
and last but most likely to start an argument oil type
my two cent any tcw-3 oil that has an engine manufactors name on it (johnson, evinrude, mercury, yamaha, suzuki,so on and so forth.)