Ok, so if I wanna go with what was spec’d in my old stuff what is your opinion? 75W-110?
Red Line 75W110 has a [email protected]
*C of 131 cSt
ISO 150 (being at lower or thinner end) gear lubricants would have a [email protected]
*C range of 135 - 165 cSt.
If your pre-2005 manual calls for 80W90
, modern day RL 75W110 may be 'considered' as meeting specs, especially in this world of Bitog/CAFE/fuel efficiency etc .
Numerically , that may be a different interpretation or judgement call .
If your pre-2005 manual calls for SAE 90
, personally I won't adopt 75W110 but hey, you make the call, not me .
In order to be closer to the original intent
of the OEM engineer who wrote the pre-2005 manual, modern day 75W140 may be a good compromise IMHO. Yes, a compromise.