In layman's terms what does the first and second number mean regarding oil (example: 5w40)
03-15-2004, 11:01 AM
#4
Elder Member
Join Date: Jun 2003
Posts: 11,377
Likes: 0
Received 0 Likes
on
0 Posts
They are both viscosity ratings - which isn't that hard to understand (more)
Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).
Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.
Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils. An example is a 10W-30 which is commonly found in stores. When choosing oil, always follow the manufacturer's recommendation.
Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.
Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils. An example is a 10W-30 which is commonly found in stores. When choosing oil, always follow the manufacturer's recommendation.
03-15-2004, 11:02 AM
#5
AudiWorld Uber User
Join Date: Apr 2000
Posts: 40,289
Likes: 0
Received 0 Likes
on
0 Posts
5 is REALLY THIN when it's cold...gets "thicker" when it warms up...
initially you want the oil to quickly flow through the engine to lubricate it and as the engine warms up, you want the oil "thicker" to protect, lubricate and cool.
"thin and thick" don't really mean that in viscosity but it's the easiest way to visualize that.
So at it's coldest, the oil is 5 weight and at its hottest its 40 weight ie 5w40
"thin and thick" don't really mean that in viscosity but it's the easiest way to visualize that.
So at it's coldest, the oil is 5 weight and at its hottest its 40 weight ie 5w40
Trending Topics
03-15-2004, 11:23 AM
#8
AudiWorld Super User
Join Date: Mar 2003
Posts: 7,550
Likes: 0
Received 0 Likes
on
0 Posts
Centipoise (cp) is the measurement for viscosity. Centistoke is cp divided by fliud density. (m)
Since the density of the liquid is a variable, I don't think there is an "easy" conversion factor.
Just my 2 cents.
Just my 2 cents.