15 is thicker oil and for bigger engines.
Yes, you can mix conventional oil with synthetic oil with no problem.
20w-50 indicates Synthetic-oil
motor oil sl cf 20w-50
Yes, I used it today.
15 is thicker oil and for bigger engines.
if it si 15w40 engine oil
20w-40
ist real oil, from the thickness and weight, it sounds like its for a diesel engine
15W40
John Deere Model B uses 20-20W oil. Some shock forks do also. I have an old Hesston Haybine that uses in the hydraulic system.
Not recommended. Use 10w30.