Originally Posted By: Gokhan
Originally Posted By: Gokhan
Regarding it won't shift to OD when it's cold: It's standard for all Toyota ATMs, including my 1985 Corolla. They won't start shifting to OD until the coolant temperature reaches 55 C (131 F) and they will stop shifting to OD if it cools to 43 C (109 F).
This thermo-switch-prohibited OD with cold engine could be to prevent oil starvation in a cold engine, as the cold oil is too thick and low RPMs could result in insufficient oil flow.
This is yet another reason to prefer a 0W-20 with a high viscosity index (low 40 C viscosity) such as TGMO 0W-20 SN to a 5W-20 or 0W-20 with a lower viscosity index (VI) such as Mobil 1 0W-20 SN.
First, 43C is not "cold engine."
Second, this cold shift logic has nothing to with oil starvation and everything to do with warming up engine/tranny/cats faster (lower emissions).