Do I need HTO/ZDDP for my old skid steer?

[Recoilfreak]

Greetings! I recently bought a mid 80's Case 1845 (no C, no S, no B - straight 1845). This thing has been served a hot supper more times than I can imagine. The service manual says to use Case TCH fluid for the hydraulics. Many current owners of these machines have told me to use 10w-30 conventional oil in the hydraulic system. The manual does say you can use 10w-30 with an HTO additive at a 20:1 oil to additive ratio. HTO is discontinued. From my research, it looks like HTO's main ingredient is ZDDP. I would like to give this little machine every chance I can at a long fulfilling life in my equipment stable. I know air in the lines can cause cavitation, which will destroy hydraulic components post haste. HTO had both anti-foaming agents and ZDDP in it - Do I need to add ZDDP to the oil? If so, what is a good alternative to HTO? Are there any good anti-foaming additives on the market today?

 

[c502cid]

I have a mid 80's Case 480D-LL tractor. I use hydraulic fluid in the hydraulics. ISO 32 since I have such a short summer.

 

[DriveHard]

Wow, lots of questions there...I'll do my best.

Chances are you are best served using a high quality hydraulic oil. No need to change to engine oil...it contains additives not needed in a hydraulic system.

Choosing viscosity is most important...look at the min and max viscosity ratings of the components in your system. Most important being the open circuit pumps. You must be able to keep them filled when cold. Then choose the proper vis. from your temperature ranges. Chances are in ISO 46 or ISO 68 will fit your needs. A hydraulic system will shear a multi-vis oil out of grade faster than you can change the oil in your Toyota.

Entrained air will wear a hydraulic system quickly, and cause really odd/bad/poor performance in several different ways, but IT IS NOT CAVITATION. Entrained air should not exist in a well designed hydraulic system, and if it does, you have a bad reservoir design, or a leak at a suction line.

If you want to talk cavitation, let me know...that is air that is fully dissolved into the fluid that comes out of suspension instantaneously to form a bubble and back into solution upon pressure changes to produce a shockwave that can destroy anything close to it. Think of a fluid going from 20 psig to -5 psig to 3500 psig nearly instantly.

ZDDP is a good additive, but it needs to be in balance - don't just go adding it to a premium fluid. Your hydraulic system contains yellow metals...things an engine does not, and they are susceptible to corrosion in different environments.

If it were my machine...
Change the filters, keep them clean
Keep heat exchangers clean
Change to a hydraulic fluid of the proper viscosity to meet your temp. requirements
...then...
Run it hard...

 

[DriveHard]

@Recoilfreak - if you have any further questions, please let me know. Most of my career was built in hydraulic systems.