zz ) m2 H. R2 Q1 t7 [7 _9 ^7 P/ r* W9 S& y- GTypically engine Manufacturers specify 10W-30 lubricants down to around -15F and 5W-30 lubricants to around -22F. These are continuous temps so spasmodically below a little won't be an issue. As others have alluded to though it may "test" the battery and starter a bit!