Nothing lasts forever, and motor oil is no exception.
After thousands of miles of driving, motor oil begins to break down and lose its ability to protect against contaminants and wear. If motor oil that needs to be replaced is left in an engine for too long, lighter molecules evaporate, leaving behind only heavier molecules that have greater viscosity. This added oil thickness can lead to wear, poor circulation, a drop in oil pressure and reduced fuel economy.
Passenger car motor oil is designed to work at 100° C or 212°
F inside the engine. To test resistance to viscosity, standard tests showed Havoline
with Deposit Shield was 10% better at retaining its viscosity than the qualifying
limit for the highest API standard*.