I want to do a gearbox oil change on my renault coupe 1.6 16v P2 and the spec says to use 75/80w, however I went to CES and they dont have it but they have a newer spec, so the guy claims, which is 75/90. Can anyone advise me on this spec or should I go for the original 75/80. Renault boxes are not the best in the world so I dont want to prematurely help it on its way to the scrap yard