Oil & Fuel Motor Oil as the Hydraulic Oil in Power Trac

[johara1]

cat eguip. NEVER used30# in the hyd. system. they used 10#.newer equipment used 15-40 in the engine and the hyd. systems.i base this on what is on the jobs and what is written in the books that come from cat.with the machine.
i retired after 40 years of running this equipment,after oct. of 2005 may be they changed.....jim

 

[johara1]

by the way, the d-9 dosers made in the 70's were d-9g and in 1975 cat had a new model d-9h. both used 10# in the hyd. the d-11n came out in 1996 the co. i worked had 12 of them and they all used 15-40 in the hyd.992-c,992-g,5110,5130,375,385 also used 15-40. those are 15 yd. loaders and 8-15 yd. hoes.these are facts.........jim

 

[MossRoad]

Hi, Jim. Good to hear from you again.

 

[KentT]

As I've described before, I'm running Amsoil 20w50 motor oil in my PT-425 and it made a quite significant increase in wheel-motor torque when the oil gets hot. I checked the viscosity ratings of several synthetic motor oils and synthetic hydraulic fluids (including Amsoil), and none of the hydraulic fluids that I found have anything close to the viscosity of this 20W50 at the normal operating temps of around 160 degrees...

BTW the synthetic motor oils have anti-shear additives (to help prevent cavitation and keep the viscosity up) in addition to anti-foaming additives. I've NEVER seen any indication of foaming in my machine, with now over 150 hours on this new fluid...

My 2 cents, your mileage may vary.

 

[J_J]

Kent, Is 160 degrees the hightest temp you have measured. How about when running the rough-cut mower for about two hours?

 

[KentT]

Kent, Is 160 degrees the hightest temp you have measured. How about when running the rough-cut mower for about two hours?

JJ, I don't have a temp guage on the system, so my "non-scientific" method was to occasionally check it with a candy thermometer when I was first dealing with the issue. The hottest I ever saw was about 180-190 and that was on a hot, humid day... But, I've never run the brush-cutter for two hours, either. My lot isn't that big.

It is typically in the 150 to 160 range, as far as I can tell. I'm not sure exactly when the cooling fan kicks on, but I think it is about 140 or a bit higher. Unless it is real hot outside (90 degrees or so) the fan seems to keep the temp under control pretty well. I've also had to replace my cooling fan -- it went out at about 350 hours...

 

[J_J]

Here is some good reading material about temperature, and viscosity.

Maximum Hydraulic Component Life

 

[funpilot]

One point I did not see anyone address but I could have missed it .... does hydraulic fluid require a different filter? Also, after how many hours, should I replace my fluid on the PT425?

 

[J_J]

One point I did not see anyone address but I could have missed it .... does hydraulic fluid require a different filter? Also, after how many hours, should I replace my fluid on the PT425?

I don't believe so, the filtration is determined by the the smallest particle that can get by. I believe your filter is a 10 micron, so therefore, anything above 10 microns in size will be filtered. Pt put a Gresen hydraulic filter in my system, but they want us to use motor oil as the hydraulic medium. You manual should tell you the frequency of change or someone that has a 425..

 

[BobRip]

One point I did not see anyone address but I could have missed it .... does hydraulic fluid require a different filter? Also, after how many hours, should I replace my fluid on the PT425?

Filter change on the hydraulics is 50 hours. You usually need to add about a quart of oil at that time. You also have to pre fill the filter and then hook up the vent hose and crank the engine with the ignition disabled until the system is bled of air. Yuu will first get fluid and then air and then fluid and you are done. Crank for 5 seconds and wait 30 seconds to allow the starter to cool.

Tansmission oil should be change about every five years. I did not really get a clear answer from PT on this.