Motor Oil weight and viscosity grade
Motor oil comes in many different weights and viscosity grades. The motor oil weight or viscosity grade, such as 10W-40, specifies the oil's thickness, or viscosity. Viscosity is basically a measurement of resistance to flow. The higher the number, the thicker the motor oil. Thicker more viscous oil tends to protect against wear better, but it can also steal horse power and gas mileage from your engine because it's harder to pump and has more drag on engine parts. Thin oil flows easier, which results in better gas mileage.
Overall, synthetic motor oil flows easier than conventional oil, which in turn provides better gas mileage. For example, 10W-40 synthetic motor oil flows much easier than 10W-40 conventional motor oil.
You should always use approved motor oil for your vehicle. Using improper oil could damage your vehicle. Always refer to your owner's manual to find the recommended oil, or contact your local motor oil dealer.
Most vehicles can operate under a small range of motor oil weights. Choosing the right motor oil for your vehicle will depend on many things, such as the climate and the driving conditions.
The most popular motor oil weights and viscosity grades are covered below:
SAE 5W-30
Climate Conditions: Performs well in sub-zero temperatures
A relatively thin motor oil that provides excellent fuel economy and low temperature performance. Used primarily in newer model automobiles. Recommended for new vehicles.
SAE 10W-30
Climate Conditions: Performs well in temperatures above zero degrees F
A slightly thicker version of 5W-30 motor oil. Frequently recommended for most automobile engines, including high-performance multi-valve and turbo-charged engines.
SAE 10W-40
Climate Conditions: Performs well in temperatures above zero degrees F
A thicker oil that provides excellent viscosity. Works well for controlling engine wear and preventing oil breakdown from oxidation. This heavier weight oil performs better in hotter climates. Typically recommended in vehicles and trucks with larger engines. Possibly a little too thick for wintertime in some cold climates.
SAE 20W-50
Climate Conditions: Performs well in temperatures above 20 degrees F
Maximum protection for high-performance, high-RPM engines because of its high viscosity. An excellent oil for hot climates and towing at high speeds for long periods of time.