15w40 viscosity comparison to AW

[MHarryE]

At Caterpillar we specify 15W-40 on many machines in high ambient (greater than 104F) applications. Some even leave the plant that way if going to high ambient temp areas. The only problem with it is cost - significantly more than typical hydraulic oils. Also some multi-viscosity oils have viscosity enhancer additives that shear down in high pressure (meaning piston pumps and motors) hydraulics. Synthetics as a rule don't use viscosity enhancer to get their multi-vis properties but once again it adds to the $$$$.

 

[Groo]

I work with a piece of machinery that uses a hydraulic cushion in a cylinder. To get that cushion to perform properly, a predecessor of mine specked a multi vis ISO 15 with a huge viscocity index... which not only was it too thin for the pump right from the get-go in the warmer months, it was quickly getting sheared down to around an ISO 9! Needless to say, I quickly had to learn more than I ever wanted to know about oil viscosity and hydraulic cushions. now that I have thicker oil working with the hydraulic cushion, I am having trouble with thick fluid, cold temperatures tripping velocity fuses. I am starting to realize why the last guy developed ulcers.

If you want to find what oils are acceptable to use, you have to know what working viscountcies the components like (usually pump and motor driven) and what temperature range you are running in the field. Basically, you have to make sure the viscosity isn't too high at start-up, and isn't too low at peak temperatures. you might even find some viscosity to efficiency charts for the pump to get the most out of your equipment.

Another thing to consider; I have heard that engine oil uses better base stock than hydraulic oil and resists wear better. I'm not so sure how true that is any more, but it wouldn't surprise me.

 

[GManBart]

I work with a piece of machinery that uses a hydraulic cushion in a cylinder. To get that cushion to perform properly, a predecessor of mine specked a multi vis ISO 15 with a huge viscocity index... which not only was it too thin for the pump right from the get-go in the warmer months, it was quickly getting sheared down to around an ISO 9! Needless to say, I quickly had to learn more than I ever wanted to know about oil viscosity and hydraulic cushions. now that I have thicker oil working with the hydraulic cushion, I am having trouble with thick fluid, cold temperatures tripping velocity fuses. I am starting to realize why the last guy developed ulcers.

If you want to find what oils are acceptable to use, you have to know what working viscountcies the components like (usually pump and motor driven) and what temperature range you are running in the field. Basically, you have to make sure the viscosity isn't too high at start-up, and isn't too low at peak temperatures. you might even find some viscosity to efficiency charts for the pump to get the most out of your equipment.

Another thing to consider; I have heard that engine oil uses better base stock than hydraulic oil and resists wear better. I'm not so sure how true that is any more, but it wouldn't surprise me.

Were the oils synthetic?

 

[DarkBlack]

The 15 in 15W40 does not stand for "15 weight". Think of the W as if it stood for "winter". The 15 and 40 have no direct relationship. It's a 40 weight oil that has a cranking resistance (not viscosity) of 15 based off a specific test standard for cranking resistance. Either way, it's a 40wt oil at 212*F, and is thicker than that at colder temps, but offers less cranking resistance than a straight 40wt would normally.

That's another TBN post that flies opposite current accepted tech norm...

 

[GManBart]

That's another TBN post that flies opposite current accepted tech norm...

I preferred your original "Yeh right...' reply.

I can't help that so many people don't know what they're talking about.

http://themotoroilevaluator.com/members-blog/understanding-multi-viscosity-oils/#axzz2qnSRfUKd

 

[DarkBlack]

I'll admit I don't work in oil. Maybe you do?
The theory That I have read, and makes sense to me regarding conventional oil ( assuming this is the subject since it is the majority?), is that the base oil has polymer additives that cause it to act like a thicker oil would be, at higher temp. If your website and inclination has you to believe it's a thicker base stock, that acts like a thinner oil when cold, then have at it. I guess it really doesn't matter for the consumer.