Since this is a "newbie" section... I just registered last night so I might be asking the wrong question in the wrong place... so sorry if that is the case. I have four used Toyotas-- 1999 Corolla, 2000 Corolla, 2000 Camry, 2001 Camry-- Have always used Castrol 20-50 in summer and 5-30 in winter...