| There
are differences in competitor’s motor oils, mainly in
the additive packages each uses. Every bottle of motor oil
is roughly 80 percent base stock 20 percent additives. The
type and amount of additives are determined by the strength
of the base stock used. Some base stock require more viscosity
index improvers than another, others need more pour-point
depressants to meet specifications set by the American Petroleum
Institute. The best motor oils to buy are the big name brands
that do not require as many additives, such as Valvoline |