Reply To: Howard 350 EP90 EP80W90 GL4 GL5 for info.

[enginear]

If Howards recommended gl4 then that is what you should use, which is more suitable for spur gears and the like
, gl5 id for diff’s, nothing to do with viscosity, also ep oils should never be used in gearboxes which have phosphor-bronze bushes as these will get eaten away by the ep, also gl5 has twice the amount of additives that will eat brass, copper and p/b.