Oil thins when heated and thickens when cooled. Choosing the proper viscosity grade for the ambient temperature of your geographic location is therefore vitally important.
A monograde is an oil whose viscosity is defined at only one temperature, either high or low. A multigrade must meet both high and low temperature viscosity requirements simultaneously.
This makes multigrades an easy and popular year-round choice for drivers who experience hot summers and harsh winters. Multigrades are easily recognized by the dual viscosity designation (i.e. 10W-30 where the 10W is the low temperature or winter designation and the 30 is the high temperature designation). It is the viscosity modifier additive that produces a thickening effect at high temperatures but is dormant at low temperatures.
Which viscosity grade is right for you?
SAE Viscosity Grade Motor Oil: 5W-30
Temperature Conditions: Below 0° F
Descriptions: Provides excellent fuel economy and low temperature performance in most late-model automobiles. Especially recommended for new cars.
SAE Viscosity Grade Motor Oil: 10W-30
Temperature Conditions: Above 0° F
Descriptions: Most frequently recommended viscosity grade for most automobile engines, including high-performance multivalve engines and turbo-charged engines.
SAE Viscosity Grade Motor Oil: 10W-40 - Castrol Magnatec
Temperature Conditions: Above 0° F
Descriptions: The first multigrade introduced. A good choice for controlling engine wear and preventing oil breakdown from oxidation. Note: Always check your owner's manual or warranty requirements before using this grade.
SAE Viscosity Grade Motor Oil: 20W-50 - Castrol GTX Extra
SAE Viscosity Grade: 20W-50 Temperature Conditions: Above 20° F
Descriptions: Provides maximum protection for high-performance, high-RPM racing engines. Excellent choice for high temperature and heavy loads such as driving in the desert or towing a trailer at high speeds for long periods of time.
SAE Viscosity Grade Motor Oil: SAE 30 & SAE 40
Temperature Conditions: Above 40° F & Above 60° F
Descriptions: For cars and light trucks, where recommended by manufacturers. Not recommended when cold-temperature starting is required.
Note: It is important to consult your vehicle handbook to establish the correct grade for your car and environment.
Why Choose a Synthetic Motor Oil?
Synthetic lubricants are engineered to do the job of a conventional lubricant, but better, as they can be specifically designed to fulfill particular needs. (see The Expert's section on THE BASICS). Though a bit more costly to produce and therefore more expensive to buy, synthetic lubricants can offer significant performance advantages because they remain stable in extreme temperatures.
Basics about motor oil
All lubricants fall into one of three categories: liquid (oil), semi-liquid (grease), and solid (graphite). All three are derived from vegetable, mineral, or synthetic base stock. However, if raw materials alone are used to lubricate modern, high-precision machinery, they quickly overheat, catch fire, evaporate or emulsify. This allows fast moving parts to come into direct contact, and can result in irreparable damage to their surfaces. To guard against this, all lubricants are processed to remove impurities and are bolstered with chemical additives.
Read more about motor oil the basics
Synthetic lubricants, however, are manufactured specifically to stand up to the severe conditions under which conventional oils might falter. They possess viscosity characteristics superior to those of mineral oils. The resulting lubricants have a molecular structure that meet and often exceed manufacturers' criteria for high-performance engines.
Among the many performance advantages that synthetic lubricants offer is their ability to remain stable at high temperatures (under which conventional oils begin to break down) and remain fluid at low temperatures (under which conventional oils begin to thicken). This provides optimum lubrication at extreme temperatures, reducing wear for a cleaner, more efficient engine.
Synthetic Motor Oil Grades
Synthetic Motor Oil Grades Synthetics are sometimes mixed with conventional mineral oils to produce a cost-effective middle ground between the two, referred to as a "semi” or “part-synthetic." However, while semi or part-synthetics and conventional mineral oils are both capable lubricants, fully synthetic lubricants provide the highest level of engine protection.
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