16. Which is better for an engine, single grade or multi-grade oil?
Generally, multigrade oil has more benefits than monograde but still depends on the one your O.E.M suggests. Most new cars nowadays are multigrade, meaning they can be used in both summer, and winter without losing their shape. If your O.E.M recommends you use monograde, stick to it because you can damage your car engine if you switch to multigrade oil.