You can improve your gas mileage by 1-2 percent by using the manufacturer*s recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.The viscosity grade (for example, 5W-30) tells you the oil*s thickness, or viscosity. A thin oil has a lower number and flows more easily, while thick oils have a higher number and are more resistant to flow. Water has a very low viscosity * it is thin and flows easily. Honey has a very high viscosity * it is thick and gooey. For a low viscosity oil such as 0w20 it produces less "drag" on the motor, which in turn can use less fuel because less work is required to be efficient.
〉 Answered on Oct 16th, 2008 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
Vehicles are developed and tested to determine what fluids are well suited for performance and
durability. If Toyota recommends 0w20 I would use that, they know best. Also there could be a warranty issue if you don*t use what they recommend.
〉 Answered on Oct 16th, 2008 by Donna Burmeister, Service Manager at Classic Nissan
The numbers used to identify different oils refers to the oils viscosity - basically how thick or thin the oil is. The difference between zero and five is very minimal. I wouldn*t see a problem with using 5. However, I always suggest that the maker of the vehicle knows best. Also, if you ever have any engine problems and it is known that you*re not using the recommended oil, it could void the warranty.
〉 Answered on Oct 16th, 2008 by Suzanne Grego, Technician at City of Philadelphia Fleet Management