Ok so my recon gearbox (94 maverick) has turned up today and I want to get the oil right I know there's probably been a lot of talk about this oil grade,I work for a motor factors so I ask for the grade i need (75-90w gl4) yes we sell it carlube 75-90w gl4/gl5 apparently it covers both gl4 and gl5,how does that work? Does anyone know if it's any good or is it best to steer clear?