15w40 viscosity comparison to AW

[bdog]

My skid steer specs 15-40 engine oil for the hydraulic fluid. How does this compare viscosity wise to regular hydraulic oils like aw32, aw46, or aw68?

 

[Chilly807]

This page has a chart that may help you. Multigrade oils are difficult to rate, but I do know that AW100 is equivalent to SAE30 viscosity-wise.

Oil Viscosity - How It's Measured and Reported

Sean

 

[oldnslo]

AW 32 is similar in grade to SAE 10
AW 46 is similar in grade to SAE 15 - 20
AW 68 is similar in grade to SAE 20 - 25

Engine oils are NOT similar in composition or additive packages to AW hydraulic oils.

 

[bdog]

Thanks for the reply. So would my 15-40 compare more like AW46 (from the 15 ) or be more like the AW150 ( from the 40)?

I am running a hydraulic motor off of my skid steer and it leaks slowly around the seal once the hydraulic temperature gets over 150 degrees or so. It does not leak when cooler than that. I was thinking maybe the oil was too thin?

 

[the old grind]

Terramite specs 15W-40 motor oil for their hydraulics. Engine oils are 'weight' tested at 212^ F to rate the second number, so 150^ sure doesn't sound too hot compared to what must be expected. Seems what works when under warranty also should afterward. btw: Engine oils are spec'ed for a 'reserve alkalinity' to inhibit corrosion ("TBN" #, .. does 'hydro' spec that?), so that or certain additives could be desired by the makers. I like the easy flow when cold (vs the NH's hydro :mur and the confidence of 40wt in my cyls on hot & dirty jobs.

This is 40wt leaking at temp, (not say AW68 or '??') tho' it seems they could be cross-compared. If not matching the spec too closely I wonder whether leaks might become worse? If it's already money on the ground, could that motor just be asking for a seal kit .. er, assuming you can spare the downtime?

 

[Chilly807]

Pretty much what he said , my understanding of multigrade oils is that they have the characteristics of the low number when cold and the high number when hot. I'd say it's time for a seal and leave the oil alone.

Sean

 

[GManBart]

Thanks for the reply. So would my 15-40 compare more like AW46 (from the 15 ) or be more like the AW150 ( from the 40)?

I am running a hydraulic motor off of my skid steer and it leaks slowly around the seal once the hydraulic temperature gets over 150 degrees or so. It does not leak when cooler than that. I was thinking maybe the oil was too thin?

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.

 

[Gary Fowler]

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.

You may be on the right track here. I remember once in Canada I decided to change the oil in my motorcycle to put in 10W40. I cranked it up and let it warm up to drain the oil which did ok, but when I started to refill it (it was about -30F) it was like pouring really cold honey. I had to take the oil inside and heat it up in boiling water to be able to get it into the crankcase. It just puddled up at the fill port and took forever to creep down, nothing like I thought 10W or even 90W oil should be.

 

[kevin37b]

Thank you Bart . I have argued this with a local brain surgeon . I will show Einstein this post .

 

[J_J]

Viscosity Charts - Bob is the Oil Guy

I will add that our Power-Tracs which have three pumps and four wheel motors, and 5 cyl have been using motor oil in the hyd systems for about 20 plus years. 10W-30, and 10W-40.

As far as I know, there have not been any failures attributed to the motor oil. Some of the Power-Trac owners are using the synthetic motor oils in the hyd systems.

Some of the Case equipment use motor oil with Case additives, and other Case machines use ATF, and others use Hy-trans hyd fluid.

The additives in motor are different that normal hyd fluid, but seem to work especially in heat tolerant.

 

[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.