My car specs 75w80 for the gearbox, it currently has 75w90 in it. Will I notice any bad effects when I switch to the 75w80? The car has 250,000km on it.
Its a Holden Rodeo. Yes its the transmission. User manual specs same oil as engine. Penrite specs HPR 5 5W-40 or Trans Gear 75W-80 (Semi-Synthetic). I would much rather use a gear oil as it's designed for gearboxes.
Originally Posted By: Jabbo
Its a Holden Rodeo. Yes its the transmission. User manual specs same oil as engine. Penrite specs HPR 5 5W-40 or Trans Gear 75W-80 (Semi-Synthetic). I would much rather use a gear oil as it's designed for gearboxes.
Pick HPR 5W40 for unconditional wear protection in ISO 100.
Pick Trans Gear 75W80 for conditional FE, as in between ISO 68 and ISO 46.
Why do you want to change a good oil which works fine? I will definitely notice some differences: more noise, notchy and possibly easier gear change, less fuel consumption in cold weather, etc. Reduced gear box life is difficult to notice, though.
At 0 Deg C approx. 500 cSt vs 750 cSt for the 75W90 but being in OZ you are probably not too concerned about that.
Who knows what the operating temperature is but say 60 Deg C it will then be approx. 27 cSt vs 43 cSt.
The thicker oil will run a little hotter anyway so that tends to reduce the difference in operating viscosity.
In a cooler climate the gear change would have been more likely to be notchy when cold. If you are experiencing that then change to the thinner oil but if not then stick with what you have.
