A higher grade number for oil means it is . A. heavier
B. more viscous
C. less viscous
D. more important

For example, a 5W- motor oil will flow better at lower temperatures than a 15W- motor oil. The higher number, following the “w” refers to hot weather viscosity, or how fluid your oil is at hot temperatures. The higher the number, the thicker the oil at a specified temperature. so it's B

Explanation:

the warning light flashes for a second or two when the engine starts. if it stays on, there's must be something wrong with the coolant. you should never dare to continue driving when the light is on. pull over as soon as possible and shut the engine off.

hope this is what you're talking about