<div class="FTQUOTE"><begin quote>Originally posted by: tramp10W is 10W no matter what number comes after it.</end quote></div>

I think you are implying that for example a 10W30 oil would have the same viscosity when cold as a 10W40 oil, just because both are 10W. This is not correct! The second number makes a big difference!!!

The "pumpability" of an oil when cold is determined by the kinematic viscosity, or cSt at 40 degrees C. Taking my two favorite oils, RedLine 10W30 and 10W40 as an example, the cSt for 10W30 is 70, where the cSt for 10W40 is 94.....that is a big difference....yet both are 10W!!! (Just for the record, 5W30 which is a very common cold weather oil, comes in at a cSt of 62.)

http://www.redlineoil.com/pdf/4.pdf

 

Do the same type of comparison for Amsoil. Second numbers make a big difference: http://www.amsoil.com/products/motoroils/index.aspx

 

ReconRanger
You are true, but all this varies with the brand and types of Oils whether dino or syn.
Your Redline as you stated numbers is way different than the cSt numbers from say Texaco dino or Royal Purple syn oils. And I recommended that the syn oils will be a better fit for winter starts. However pour point degrees are very similar on the 10W oils, again no-matter what the second number is. Thanks for pointing that out.
You are Good.

 

<div class="FTQUOTE"><begin quote>Originally posted by: JDQuadRider
My local Honda dealer recommends that I always run 10w-40 in the Rubicon which seems a little suspicious to me.</end quote></div>

I would consult the oil viscosity chart in my owner's manual, before I would believe anything a dealer had to say. For my Hondas, 10W40 covers from the teens F on the low end, to up over 100 degrees F on the high end. Sure, that's a pretty broad range, but it is best to pick an oil weight where your ambient temperature range will be in the middle of the range on the oil chart. That gives you lots of "wiggle" room, both in the hotter and colder directions.......

But, most folks don't even change their oil once a year, much less change to different oils for the cold/hot seasons!

 

Thanks Ranger! I remember you covering this topic with me in a different thread and this is the reason I even bring it up. I still don't know why they'd tell me to always run 10W-40 in my rubicon.

On a side note, I've never bought Amsoil before and I'm curious to know where people buy it?

 

JDQuadRider
Don't even think about Amsoil...........just my personal experience. Don't want to start a big argument........like I say, just my personal experience.
If you are going to a syn oil, go with (ReconRanger's) Redline, Royal Purple or Maxxium.
Amsoil is mostly only avalible thru (Amway) Uoops, Amsoil dealers.

 

The "pumpability" of an oil when cold is determined by the kinematic viscosity, or cSt at 40 degrees C. Taking my two favorite oils, RedLine 10W30 and 10W40 as an example, the cSt for 10W30 is 70, where the cSt for 10W40 is 94.....that is a big difference....yet both are 10W!!! (Just for the record, 5W30 which is a very common cold weather oil, comes in at a cSt of 62.)

 

I have a 2003 Rubicon facotry manual sitting around. It has a chart that shows 10W-40, 10W-30 good down to 15f and SAE 5W below that.

Since it has a centrifugal clutch, I wouldn't use anything with molly or ptfe.

Since the thing holds over 5 quarts of oil and since the winter weight isn't likely to be in there very long, I personally probably wouldnt' shell out the big bucks for synthetic, but that's just me.

Quite a bit of water from condensation can build up in a motor that's only run for short periods in cold weather, so frequent changes would be in order.

 

The "pumpability" of an oil when cold is determined by the kinematic viscosity, or cSt at 40 degrees C. Taking my two favorite oils, RedLine 10W30 and 10W40 as an example, the cSt for 10W30 is 70, where the cSt for 10W40 is 94.....that is a big difference....yet both are 10W!!! (Just for the record, 5W30 which is a very common cold weather oil, comes in at a cSt of 62.)



Reconranger
The more I got to thinking about your quote, the more something was bothering me about it. So having to dig out my antique Chem books, I guess we will have to agree to disagree.
The cSt viscosity refers to the sheering strenght of the oil at a particular temperature. The ability of an oil to more about the engine is more related to the Pour Point. And an oil with a 10W, again no matter what number follows is the same pour point.
Example: 10W-30 has a pour point of -25degrees.
10W-40 has a pour point of -25 degrees.
5W-30 has a pour point of -30 degrees.
Syn 5W-40 has a pour point of -40 degrees.

 

Since the book lists straight 5W, I'm sure a good 5W30 would give excellent performance in the winter. Since he's talking about plowing (low speed, high engine load) I would guess that the oil temp would eventually get up there where 5W might be less than optimal.

Man, this got way off track from the original topic of 420 EFI starting in cold weather...