Originally Posted By: jldcol
You can treat syn oil as 1 weight lower, here 10w syn~5w dino. That's group 3 syn, real syn probably 2 weights lower~0w, which doesn't exist as a dino yet. There are 6 winter weights, 25 20 15 10 5 and zero. I would say there are 3 winter climes mild~30-50 degrees, Hawaii? cold zero-32 degrees and frigid below zero. 25 and 20 ok in the mild winters, 10 and 15 ok in cold winters, and 5 and zero wt. in frigid cold winters. All these are for dino oils, syn's 1 catagory colder ok, so 10w syn, I would think ok to below zero, perhaps -10 degrees.Amsoil seems full syn stuff so maybe even a bit lower.
That is utter non sense. Look at the data sheets. Synthetic 10w-30 like Amsoil ATM is not going to pass the 0w SAE cold cranking test. It might pass the SAE mini rotary viscometer for 5w.
By definition 10w is safe to -13F.
I'd say a synthetic 10w-30 with a CCS below 4,000 cP :MIGHT: get the job done in the SAE 5w CCS test (-22F), so I'd say a safe limit for 10w-30 synthetic would be between -13F and -22F.
Not a snowballs chance in [censored] it would suffice in conditions needing an actual 0w oil.