Oil Weights

[cacmasta]

First I will list the different weights of oil you may come across and then I will go into detail on what the numbers stand for and when you should use which.

5w-20*
0w-30, 5w-30, 10w-30
5w-40, 10w-40, 15w-40, 20w-40
5w-50, 10w-50, 15w-50, 25w-50
10w-60, 15w-60, 25w-60

* used in 7th gen civics

Now that we know the variety, what is oil weight?
Oil weight, referred to as viscosity, refers to how thick or thin the oil is. The more viscous the oil, the thicker it is and therefore has a higher resistance to flow.

But what do the ?w? and numbers stand for?
The Society of Automotive Engineers (SAE) has set a temperature requirement for oil.
-32?C (0?F) (low) to 100?C (212?F) (high)
Oils that meet the low temperature requirements have a ?w? after the viscosity rating. Oils that meet the high temperature requirements do not have a letter after the viscosity rating.

Now that we know what the ?w? stands for, what do the numbers mean?
The numbers represent the oil?s viscosity rating.

How is oil rated for viscosity?
A set amount of oil is heated to a specific temperature (within the requirements set by SAE). The oil is then allowed to flow out of a specified sized hole. Viscosity rating is determined by the length of time (measured in centistokes) it takes for the oil to completely flow through the hole. If the oil flows quickly, it receives a low rating (i.e. 5) which means the oil is very thin. If it flows slowly, it receives a high rating (i.e. 60) which means the oil is very thick.



Most people use what is known as a multi-grade oil. All of the weights listed about are multi-grade oils. Multi-grade oils meet the SAE specifications for the low temperature requirement for light or thin oil and the requirements for the high temperature of heavy or thick oil.

Most new engines today require 5w-30 for all around driving. It contains friction reducing additives to help improve fuel economy, and also allows the oil to be thin enough to reach critical valvetrain components when a cold engine is first started without being too thin as to where the oil provides no protection. This is highly important since most engine wear occurs at cold temperatures.
For older engines and ones that are driven at sustained highway speeds during hot weather, a 10w-30 or 10w-40 oil is good. Heavier multi-grade oils such as 20w-40 are for high RMPs (all you racing and track addicts) and are not recommended for cold weather driving.

If you don?t want to use multi-grade oil, you can still use straight weight oil (30w and 40w), but they aren?t very popular anymore due to being too thick for cold weather (switching to a 20w for cold weather driving is necessary) and may make an engine hard to start. They do, however, hold up better under high temperature, increases in oil pressure and reduce oil consumption in high mileage engines. At the other end, straight low oil can improve cold weather starting, but is very thin and should only be used in sub-zero climates.

My recommendation:
If you have a 5th or 6th gen, stick with a 10w-30 unless you plan on racing or visiting the track often, then you may want to move up to a 20w-40. If you live in an area where you have cold winters, change your oil back to 10w-30. IF you have a 7th gen civic it?s best to stick with the 5w-20, but again if you plan on racing quite a bit, 5w-30 or 5w-40 may not hurt your civic.

NOTE: I am not a mechanic so don't hold me to my reccomendation. It's just my opinion.

Sources:
www.netstang.com
www.valvoline.com
www.autosite.com

[Calesta]

Great writeup!