OIL VISCOSITY
Viscosity is defined as the rate of flow of the oil or lubricant. Most carmakers
use multi-viscosity oil, which adjusts its rate of flow based on outside temps and
internal engine temperatures. Always use the recommended viscosity oil for
your vehicle. For instance, on many of their engines Ford recommends the use of
5W-20 semi-synthetic motor oil. Why? Because of tight internal engine
tolerances and elevated combustion chamber temperatures designed to achieve
lower tailpipe emissions. If you use anything else in the engine and it fails, then
Ford will deny warranty claims. I have seen this happen time and again. Follow
recommendations so your warranty stays intact.
Carmakers specify types and viscosities of oil for their engines. For example,
GM uses Mobil One Synthetic in its Corvette engines. Whatever the carmaker
suggests, use it! Both the carmakers and the oil companies have done significant
lab testing to determine exactly what type of oil to use in their powerplants.