Yes, I used it today.
Yes, you can mix conventional oil with synthetic oil with no problem.
if it si 15w40 engine oil
Not recommended. Use 10w30.
Use 15w40 motor oil unless specified otherwise
10w-40
Castrol 10 30
Can be either Mobil 1 0W40 or Any name brand 15w40
I use 15w40
10W40 or 15W40
15w40
A diesel engine would use 15w40 a gas engine could use 15w40 or 10w40
I use 15w40