Oil is not well
QI recently bought some EP90 gear oil for my Triumph GT6. I’ve just noticed it’s of modern GL5 specification, not the older GL4 recommended in the manual. Is it OK to use? Albert r Hall, porthcawl
AWe understand that GL5 oil can be used in a GT6’S gearbox, but not in the rear axle or overdrive. The sulphur additives in the oil can attack the copper components of these assemblies at higher temperatures. If you can’t find GL4 at a mainstream motor factor, contact a classic oil specialist or see if a local agricultural supplier stocks it for tractors and machinery.