Fuel Economy Linked to Oil Viscosity

In Magazine Rack by Dan BandimereLeave a Comment

What explains the downward trend in oil viscosity (weight)?  The demand to increase fuel economy is by far having the greatest impact.  A generation (or two ago) SAE 10, 20, 30, 40 and 50 were the norm, then multi-weight oils were introduced offering the best of both worlds as a result of VI or viscosity Index Improvers for safer cold weather starts and searing summer protection.

Multi-Grade Oils :    VI improvers ushered in multi-grade oils like 10W-30, 10W40, 5W-30, 5W-20 and now even 0W-20.  The quality of VI improvers are directly related to a term called “shear”.   Shear occurs when oil is forced through narrow passages, such as between piston rings and cylinder walls.  Low quality VI improvers are prone to two significant problems: 1) they thicken the oil at low oil temperatures; 2) Subject to excessive shearing causing oil viscosity loss which equates to reduced lubricant protection between critical high wear parts.

Thin is In:   Since 1973 when OAPEC announced the oil embargo against the U.S. our world has never been the same regarding the by-products of petroleum – IE fuel, lubricants etc.  Our federal government, in their quest to “protect” us and reduce our dependance on foreign oil, created the CAFE standards requiring OEM’s to increase the average fuel economy of passenger vehicles to 18 mpg’s in 1978.  Now in 2016 it will have increased to 35.5 mpg.

To meet this requirement OEM automakers will continue to built smaller cars, smaller engines with “critically” narrow oil passages requiring lighter viscosity oils that can withstand the rigors of American drivers.

Quality is key: 



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