Do you know how well a 20 weight motor oil protects compared to a 30 weight oil as far as temperature goes?

Thanks.Do you know how well a 20 weight motor oil protects compared to a 30 weight oil as far as temperature goes?
Are you talking about ';single grade'; (20 or 30) or ';multi-grade'; (10W30)?





30 is a heavier oil than 20. I wouldn't advise using anything above 20 unless you have a real oil pressure problem in an engine you don't care about (eventually you'll blow seals)





Try checking out Valvoline's website.Do you know how well a 20 weight motor oil protects compared to a 30 weight oil as far as temperature goes?
20 weight will protect it a lot better ,because its a lot thinner based,especially in the winter time,i usually use a 10-w-30 all year round then i don't have to worry about it,it will just give you better warm ups ,its a good oil to use,but you can check in the owners manual and see what it calls for,that's what i recommend before you change the weight of it,read the manual and see what it says.good luck.
straight 30 weight isnt used that much anymore..





Oil Viscosity


The viscosity of multi-weight motor oil is specified using two numbers. The first number is the viscosity when the oil is cold. This is followed by the letter W (which stands for winter, not weight), which is followed by the number that indicates the viscosity when the oil is at operating temperature. The higher the number the thicker the oil.





Viscosity Modifiers


In order to protect an engine at start time, the oil needs to be thinner when cold so it flows freely. Viscosity modifiers are added to the base stock to make the oil flow better when cold, without making the oil too thin when hot.





Climate Considerations


Owner's manuals and service manuals will specify the acceptable oil to use at various temperatures. In warm climates, 10W30 is usually an acceptable alternative to the preferred 5W30 and may be used without measurable adverse effects. In the olden days, before multi-weight oils, it was common to have a winter oil and a summer oil. This is no longer necessary, but if you normally use 10W30 because you live in a warm climate then be sure to switch to 5W30 if you plan on using the vehicle in very cold weather.





5W30 versus 10W30


Virtually all new passenger vehicles sold in the U.S. use either 5W30 or 10W30 oil. The difference between the two is that the 5W30 flows better when cold, so if you live in a cold climate or operate your vehicle in a cold climate during the winter months, you should use 5W30 if it is the preferred oil for your vehicle. If you live in a sub-tropical climate and don't operate your vehicle in cold climates, then 10W30 is acceptable as long as the manufacturer specifies that it is permissible to use it.





Is there a disadvantage to using an oil that flows better when cold, i.e. 5W30 versus 10W30?


Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer's recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.





Why do many oil change places, even dealerships, use 10W30 instead of 5W30, even when 5W30 is preferred?


According to www.cartalk.com (see link in the references section), as well as many mechanics who have posted on usenet, 10W30 is the closest thing to a one size fits all oil. Many older vehicles need 10W30, and most newer vehicles are okay with it in warmer climates. Since many garages don't want to have multiple tanks of bulk oil they choose to carry only 10W30. The advice that Tom %26amp; Ray give is correct, 'it would not be a disaster if you used 10W30, but given a choice, go with the manufacturer's recommendation and use the 5W30.'





Thicker is Better Myth


The reason that oil viscosities have gotten thinner is because bearing clearances have become smaller. Using thicker oils will interfere with oil flow and the oil pressure will increase. In a worn engine it may be okay to increase the viscosity of the oil because the bearing clearances have become larger.
If you r car recommends a sae20 weight oil it is best to stick with that oil,the out side temp does not really affect the viscosity(thickness) of your oil it is the internal temperatures that have an adverse affect on your oil when the temperature inside of your engine exceeds the thermal breakdown rating of your oil the oil will lose its ability to protect by becoming thinner as it heats up,at normal temperatures the oil maintains its advertised sae weight rating,oils today usually have very high thermal thresholds at or above 600 degrees with synthetics as high as 750 degrees and many racing oils above 800 degrees so unless you are really working you engine you should not need to change the recommended weight of oil in your car.
why are you wasting time with mono-grade oils? unless you have a specific application, in which case you would be best using what is suggested by the manufacturer





modern multi-grade oils are so much better with less hassle.