Runny Oil
Senior User
Joined: Apr 2001
Posts: 321
Likes: 1
Runny Oil
Hi,
I know very little about oil, but always thought that 10 W 30 meant that the oil had 10 "weight" when cold, and 30 "weight" when hot.
If this is true, how come when I change my oil and it is warm, it runs out like it is 0 W, just like water?
If it gets a higher viscosity when warm, why does it thin out?
I quickly looked throught the archives but could find no explination.
Thanks!
-Brents
I know very little about oil, but always thought that 10 W 30 meant that the oil had 10 "weight" when cold, and 30 "weight" when hot.
If this is true, how come when I change my oil and it is warm, it runs out like it is 0 W, just like water?
If it gets a higher viscosity when warm, why does it thin out?
I quickly looked throught the archives but could find no explination.
Thanks!
-Brents
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
Runny Oil
Hot oil is thin. You probably can't tell the difference between hot 30 weight and 50 weight. The key is that at temperature the oil will have the protection and antiburn characteristics required. Synthetics are very thin but they still have the appropriate ratings.
The clearances in an engine are very tight, thinner than a sheet of paper in many cases. An oil that is visibly thick while hot will not slow through those tight clearances and thus you get no protection.
Believe the can lable and use what your manual calls for. Millions of dollars have been spent by many oil companies to make sure their oils meet this very basic requirement.
Good Luck,
Jim Henderson
The clearances in an engine are very tight, thinner than a sheet of paper in many cases. An oil that is visibly thick while hot will not slow through those tight clearances and thus you get no protection.
Believe the can lable and use what your manual calls for. Millions of dollars have been spent by many oil companies to make sure their oils meet this very basic requirement.
Good Luck,
Jim Henderson
Senior User
Joined: Sep 2001
Posts: 238
Likes: 0
From: Troy USA
Runny Oil
Also....
The numbers do not quite mean what you said. A 10W30 oil for example, is suppose to flow like a 10 weight oil would when cold... and flow like a 30 weight oil would when hot.
This does not mean the oil is thicker when it is hot than when it is cold. It just means it flows the same as the straight weight oil would at the same temp. In other words, if you took a 10 weight oil down to 30 degrees, the 10W30 would flow this way. If you too a 30 weight oil up to 200 degrees, the 10W30 would flow that way.
But, what this also means is that a 30 weight oil at 200 degrees will be thinner than a 10 weight oil at 30 degrees.
Clear as mud!
The numbers do not quite mean what you said. A 10W30 oil for example, is suppose to flow like a 10 weight oil would when cold... and flow like a 30 weight oil would when hot.
This does not mean the oil is thicker when it is hot than when it is cold. It just means it flows the same as the straight weight oil would at the same temp. In other words, if you took a 10 weight oil down to 30 degrees, the 10W30 would flow this way. If you too a 30 weight oil up to 200 degrees, the 10W30 would flow that way.
But, what this also means is that a 30 weight oil at 200 degrees will be thinner than a 10 weight oil at 30 degrees.
Clear as mud!
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