I currently work for a ready-mix co. and run a outpost garage. The main garage insists on a hyd. system drain and filter change at 1000 hour intervals on mixers. I contend that a filter change at the 500 hour service mark with the oil top off is better because the oil is already cleaner than what comes from my tank. I say that hyd. oil doesn't wear out like crankcase oil and doesn't need changed. I remember magazine articles several years ago where Cat recommended not changing hyd. oil, only filter changes because of bulk oil contamination and a hyd. system is a closed multi pass filtration system where the oil is currently filtered. FWIW I run 1751 NAPA filters on the suction.
Are you sampling? I don't, but should. That would be the best way to determine what condition the oil is in.
Sample, kidney loop (filter cart) reuse.
No sampling, yeah we probably should but don't. I'm talking more in general terms though, if metal isn't there,what is to be gained by a fluid change? I contend that hyd. oil doesn't just wear out.
Well Lan, the reuse is in the old Reznor furnace so it isn't a waste, just "repurposed". My thoughts are short of contaminates(metal) which indicate impending doom, the oil is good indefinitely. A fluid change will just temporarily mask a problem that may be there. I like the kidney loop but there just isn't time to make one.
The base oil does not, but the additive package gets used up, and the oil can get contaminated with nonmetallic, non filterable chemicals or minerals that the oil sampling will show. If you're using an AW oil, which is supposedly "Anti-Wear" the substances added to make it antiwear and antioxidant do go away over time. Water will also get entrained and can cause serious issues. I do agree on one point, change filters often, they're cheap, pumps and motors are not.
You make a excellent point about the AW additive package getting used up and I realize that those sundstrand pumps are $$$. What I don't understand is how Cat would say don't change oil, only filters, maybe top off oil replenished the AW package? Oh well, maybe my muse carries me to some obscure subjects.(it does)!
LOL @ obscure subjects! I think as far as the CAT deal, you're back to changing oil based on periodic sample analysis, that would make sense to me. Yeah, the dealer I worked for sampled their bulk tanks and SOS truck tanks, found contamination, sampled the bulk truck tanks from the distributor, they all came back with high silicon (dirt) so they added 3 micron filters to every system.
If I can butt in here..... The Cat recommendation (if it's the same one I remember) is that you can go up to 4000 hours on hydraulic oil just changing filters at regular intervals, probably 500 hours, provided you are sampling. The oil then gets changed based on condition as shown by the sample analysis results not hours but in any event there is a limit beyond which you don't go, because as lantraxco pointed out the base oil stock may not deteriorate but the additive package does.
No oil supplier AFAIK meets Cat's 16/13 ISO standard for fill oil cleanliness right from the get-go. Every place I've ever worked has either had a constant recirculation or a single pass filter system between the bulk tanks and the shop. I prefer the constant recirculation system personally.
I agree with Nige, no oil except small bottles is "clean" as it comes off the truck. You should always filter oil - the simplest is an end of line filter, one step better is a good filter cart, but a kidney loop on a tank will do the best job. From what I have seen CAT and Deere are pushing their dealers to do this and use 3 micron breathers. FYI - some distributors will filter the oil for an extra fee. Also agree on additive wearout and contamination as reasons to change oil. ISZ
Is there an AW additive one can add? I have some cat stick something additive to make the Pistons glide easier, is that good?
There are all sorts of snake oil available on the market that will cure everything according to the companies whop market them. I've never found one that was worth thinking about TBH.
Thank you for this great info. I'm new to heavy equipment ownership and want to make sure I do things right. I have just purchased an older 1845C for use on our property and I'm working my way through the servicing.