the viscosity difference is significant ONLY below -30F. The spec is max 10,000 Brookfield at -40 and the Valvoline stuff is slightly more viscous, but WILL work fine.
IF one were to use 'vintage technology' ATF fluid (like the store brand at a no-name quick-stop that sells freid food, etc along with fuel,) that stuff would probably NOT flow at all at -20F
If Valvoline claims it will work, you CAN book it. They would cover repair for a lube quality related (toohigh viscosity failure. This WAS a problem for ATF's some 5-6 years ago when the electronically controlled transmissions were introduced. At very low temperatures, they would not go into gear for maybe a minute. People would put it in gear in extremely low temperatures (-20F)--no go--then put it in Neutral, get out--an THEN the transmission woulg go into gear as had been requested.
The 'fix' by GM was to tighten up the low temperature viscosity requirement a lot. In order to meet the new specs, very high VI base oil was needed. previously only available from true synthetics like PAO's). Now severely hydro-processed petroleum base oils offer nearly identical viscosity and wear protection performance at much less cost, and constitute perhaps 90% of the ATF base oils today. The additive packages are almost all identical -excepting AMSOIL, Royal Purple and a few other very very high performance products.
IF one were to use 'vintage technology' ATF fluid (like the store brand at a no-name quick-stop that sells freid food, etc along with fuel,) that stuff would probably NOT flow at all at -20F
If Valvoline claims it will work, you CAN book it. They would cover repair for a lube quality related (toohigh viscosity failure. This WAS a problem for ATF's some 5-6 years ago when the electronically controlled transmissions were introduced. At very low temperatures, they would not go into gear for maybe a minute. People would put it in gear in extremely low temperatures (-20F)--no go--then put it in Neutral, get out--an THEN the transmission woulg go into gear as had been requested.
The 'fix' by GM was to tighten up the low temperature viscosity requirement a lot. In order to meet the new specs, very high VI base oil was needed. previously only available from true synthetics like PAO's). Now severely hydro-processed petroleum base oils offer nearly identical viscosity and wear protection performance at much less cost, and constitute perhaps 90% of the ATF base oils today. The additive packages are almost all identical -excepting AMSOIL, Royal Purple and a few other very very high performance products.
