SAE 20W-40 were temperatures are consistently above + 32degrees Fahrenheit.
SAE 10W-30 or SAE 10W-40
Suitable for year long operation in many parts of the U.S., may be used where Temperatures occasionally drop as low as - 10 degrees Fahrenheit.
SAE 5W-30 or SAE 5W-20
Recommended where minimum temperatures are are consistently below + 10 degrees Fahrenheit.
SAE 30 were temperatures are consistently above + 32 degrees Fahrenheit.
SAE 10W were temperatures range between + 32 degrees Fahrenheit. and -10 degrees Fahrenheit.
Oil viscosity recommendations for the 426 cubic inch Hemi Engines
SAE 20W-40 Where temperatures are consistently above +32 degrees Fahrenheit.
SAE 10W-30 or 10W-40 were temperatures are consistently below +32 degrees Fahrenheit.
SAE 30 or SAE 40 Where temperatures are consistently above +32 degrees Fahrenheit.
To keep it simple, The accumulation of contaminants in the oil and chemical changes in the oil itself.
Some other reason can be:
Common Contaminants (dust and dirt )
Internal Forces To learn more about oil visit: http://www.sae.org/
Synthetic oil is comprised of man made chemicals that are added to natural crude oil. Synthetic oil is a more pure form of oil than other motor oils.
Using Synthetic oil in place of conventional will result in fewer oil changes as well.
Synthetic oil should also give you better fuel mileage.
Synthetic oil can also withstand higher temperatures than conventional oil can. This is very important if you care about the longevity of your engine.
Synthetic oil obviously cost a little more, but it is well worth the extra money for a well maintained daily driver.
Whats your opinion? Let us know in the Mopar Forum Room.