A. Lower viscosity oils or oils with a lower W rating such as 10W-30, 5W-40 or 5W-30 can be formulated for both engine durability and fuel economy.
When a low viscosity oil can demonstrate proven engine durability, the benefits of significant fuel savings while sustaining optimum engine life is achievable. However, emphasis needs to be placed on how the oil is formulated and tested. Just lowering the viscosity grade without providing a performance enhancing additive technology could lead to higher engine wear and shortened engine life.
With the push to improve fuel economy, the unknowing consumer may be inclined just to listen to the fuel-saving message and not check out product performance support behind the claims.
Overall, properly designed, low viscosity heavy-duty engine oils can provide fuel savings, reduce cold engine cranking with reduced dependency on energy consuming block heaters, and improved battery and starter life, reduce cold weather start wear and superior high temperature performance.