In the late 1970s, when I first started working on cars and doing engine maintenance, 10W-30 was about the only ...

Yet, its motor oil products are limited to just two lines, namely its Pro Performance conventional oil and its SYN Full Synthetic oil, each available in grades of 5W-20, 5W-30, and 10W-30.

Selecting the proper viscosity of oil also has an effect on fuel mileage. For instance, pouring 15W-30 motor oil into an engine that requires 0W-30 will lead to excess friction during cold ...