Heavy Viscosity Oil Has Very Limited Application

Today, such heavy oils are recommended only for high-performance engines or to reduce oil loss in older engines.

Engines have changed dramatically in the past l5 years and so have the manufacturers' recommendations on oil use.

Today, General Motors, Ford and Chrysler do not recommend 20W-50 for any new car or light truck. They don't because 20W-50 doesn't flow fast enough to adequately protect the engine. What the auto makers do recommend is 5W-30 for winter, and l0W-30 for summer.

How well an oil flows through an engine to protect its vital parts is known as "pumpability."

Thicker oils, like 20W-50, have "poorer pumpability" and in cold weather, can't flow fast enough to reach vital areas needing lubrication. Then, metal-to-metal contact can occur, damaging the engine.

Oils like 5W-30 and l0W-30 have the "right pumpability" so they flow faster, and reach vital engine parts quicker for complete lubrication.

Some people still mistakenly recommend 20W-50 for today's smaller, higher-revving engines because they believe it provides better protection against engine wear. This is simply not true.

Numerous industry tests prove that Pennzoil 5W-30 and l0W-30 provide the same protection against engine wear as 20W-50. And because 5W-30 and l0W-30 flow faster and provide quicker lubrication, all U.S. manufacturers recommend them for today's engines.