Let's revisit the oil vs. hydraulic question???

[perry]

I'm still running hydraulic fluid, but plan a swap to motor oil soon but. I have one question about motor oil before change over. I have an old heavy duty cast iron two stage air compressor, and after a few years it started taking longer to fill the tank, so I purchased a rebuild kit and during the tear down I couldn't believe the carbon build up in the cooling lines from first to second stage. I soon learned that only 'compressor oil' should be used, it will not produce carbon build up. 'NEVER' use motor oil in compressors. It's the high pressure that causes carbon build up.
Could motor oil have any adverse effects in 853?. It would definitely be under high pressure!.

Thanks

 

[Butters]

I would think that in a compressor you are compressing and heating air with some blow by oil vapor and oxidizing it. In an machine, the oil should not be mixing wiht high pressure, hot air.

 

[Tazza]

I would think that in a compressor you are compressing and heating air with some blow by oil vapor and oxidizing it. In an machine, the oil should not be mixing wiht high pressure, hot air.

You beat me to it. I was going to point out that compressors compress air but in a good working hydraulic/hydrostatic system there is no air trapped.
Essentially with a compressor when its warm, its like a diesel engine. High compression of an air charge and if your rings were worn you can get oil in the chamber which is essentially fuel. Thats probably where the carbon came from, small detonation of the oil. So small that you wouldn't even notice it.
Slightly off topic but i know a guy with a HUGE compressor used in the mines. It exploded when there was a problem with oil that essentially had the *diesel* effect. High compression and oil for lubrication and it went BOOM. Did a reasonable amount of damage too.

 

[perry]

You beat me to it. I was going to point out that compressors compress air but in a good working hydraulic/hydrostatic system there is no air trapped.
Essentially with a compressor when its warm, its like a diesel engine. High compression of an air charge and if your rings were worn you can get oil in the chamber which is essentially fuel. Thats probably where the carbon came from, small detonation of the oil. So small that you wouldn't even notice it.
Slightly off topic but i know a guy with a HUGE compressor used in the mines. It exploded when there was a problem with oil that essentially had the *diesel* effect. High compression and oil for lubrication and it went BOOM. Did a reasonable amount of damage too.

Tazza, when you change out motor oil in your bobcat, is it black?, and how often.

 

[OldMachinist]

Tazza, when you change out motor oil in your bobcat, is it black?, and how often.

Now I know I'm going to hear that Bobcat recommended for years that you use motor oil in hydraulic systems but this is what I was told by a chemical engineer at Engineered Lubricants in St. Louis, MO
"You never want to use a detergent oil in a hydraulic system - it can cause anything from foaming in the oil which will cause cavitation in the hydraulic pump and result in premature pump failure, to it picking up waste/contaminants in the oil and depositing it as sludge throughout the hydraulic system. EVERY multi-grade oil available in the US is going to be detergent oil and they have no anti-foaming additives in them. All high quality hydraulic oil have anti-forming additives."
I hope we can someday put this issue to bed as it seems to come up at least once a month here.

 

[Tazza]

Tazza, when you change out motor oil in your bobcat, is it black?, and how often.

Perry - yes, its always black. I don't do a lot of hours on my machines but i do try and keep up to date on servicing. Oil is cheap and i like to keep my engine oil nice and clean.
My manual says to change it every 50 hours! but others say 250 is more like it. I like to change it often enough so its not jet black and when you have changed oil and the filter the oil is still the rite colour. I like to change it before its so black that you can't see through it anymore but thats just me.
The oil debate i doubt will ever be resolved, i guess it is just personal preference.
As for sludge, i wouldn't believe that, remember ALL the oil is filtered constantly so any sludge would be filtered out. Anti-foaming in a hydraulic system isn't an issue, when the air is all removed there is absolutely no reason for it to foam up so no need for that additive. I have run 15W40 diesel engine oil, it runs detergent as its for diesel engines and i have never had an issue!.

 

[OldMachinist]

Perry - yes, its always black. I don't do a lot of hours on my machines but i do try and keep up to date on servicing. Oil is cheap and i like to keep my engine oil nice and clean.
My manual says to change it every 50 hours! but others say 250 is more like it. I like to change it often enough so its not jet black and when you have changed oil and the filter the oil is still the rite colour. I like to change it before its so black that you can't see through it anymore but thats just me.
The oil debate i doubt will ever be resolved, i guess it is just personal preference.
As for sludge, i wouldn't believe that, remember ALL the oil is filtered constantly so any sludge would be filtered out. Anti-foaming in a hydraulic system isn't an issue, when the air is all removed there is absolutely no reason for it to foam up so no need for that additive. I have run 15W40 diesel engine oil, it runs detergent as its for diesel engines and i have never had an issue!.

Foam in the hydraulic system isn't always caused by air entering the system. Bubbles can form when the oil is forced over the relief valve and any place in the system that it is forced through small orifices under high pressure. With out anti-foaming additives these bubbles can stay suspended and be sucked back through the pump causing cavitation in the pump. Again this is from my conversations with same engineer. I had this conversation with him last month after I told him about the debates about oil that we have.

 

[jklingel]

Foam in the hydraulic system isn't always caused by air entering the system. Bubbles can form when the oil is forced over the relief valve and any place in the system that it is forced through small orifices under high pressure. With out anti-foaming additives these bubbles can stay suspended and be sucked back through the pump causing cavitation in the pump. Again this is from my conversations with same engineer. I had this conversation with him last month after I told him about the debates about oil that we have.

I have a question about diesel engine oil. When I checked my engine oil after the first change, I was surprised to see how black it was after 500 miles (Ford International p/u engine). The dealer told me "Normal. Happens in 10 minutes." When I check oil on my loader, it looks brown and fairly clean for a hundred hours or so. That concerns me; it is like it really isn't circulating, but obviously it is. Do loaders just run cleaner, in general, or does it vary from engine make to engine make? I bought this loader w/ 1200 hrs on it, so it is not a "new engine, tight rings" situation. Just curious.

 

[Tazza]

I have a question about diesel engine oil. When I checked my engine oil after the first change, I was surprised to see how black it was after 500 miles (Ford International p/u engine). The dealer told me "Normal. Happens in 10 minutes." When I check oil on my loader, it looks brown and fairly clean for a hundred hours or so. That concerns me; it is like it really isn't circulating, but obviously it is. Do loaders just run cleaner, in general, or does it vary from engine make to engine make? I bought this loader w/ 1200 hrs on it, so it is not a "new engine, tight rings" situation. Just curious.

Its really hard to say. I have had engines that kept the oil quite clean but i have had others that were always dirty. Change the oil and its black pretty fast.
In a diesel it is normal for the oil to get black fast, not sure what makes some worse than others. I would suspect wear but i can't say that for sure..
I don't know enough about hydraulics to know just how oil reacts under high pressures. I still don't understand how you can get foaming when the oil is under suction, where does the air come from to cause the bubbles in a closed circuit? I understand how cavetation causes problems to hydraulic components when the bubbles implode under pressure so its not a thing you want happening a lot!.

 

[OldMachinist]

Its really hard to say. I have had engines that kept the oil quite clean but i have had others that were always dirty. Change the oil and its black pretty fast.
In a diesel it is normal for the oil to get black fast, not sure what makes some worse than others. I would suspect wear but i can't say that for sure..
I don't know enough about hydraulics to know just how oil reacts under high pressures. I still don't understand how you can get foaming when the oil is under suction, where does the air come from to cause the bubbles in a closed circuit? I understand how cavetation causes problems to hydraulic components when the bubbles implode under pressure so its not a thing you want happening a lot!.

The bubbles aren't always air. When you force liquid through a orifice at high pressure gas bubbles can form.

 

[OldMachinist]

The bubbles aren't always air. When you force liquid through a orifice at high pressure gas bubbles can form.

I should add that hydraulic fluid is formulated to withstand the high pressures(upto 5,000 psi) of the system. Engine oil pressures are less than 200 psi. Also most hydraulic oils have fire-retardants added these days.

 

[Tazza]

I should add that hydraulic fluid is formulated to withstand the high pressures(upto 5,000 psi) of the system. Engine oil pressures are less than 200 psi. Also most hydraulic oils have fire-retardants added these days.

After this, i can see the whole "can of worms" starting
Will be interesting to see if we can actually get the *rite* answer for all this.
When you say engine oil is only made to withstand 200 psi or so, what difference is there between that and hydraulic oil? I just can't see any difference as they are both liquid so they can be compressed essentially indefinitely. I just don't understand how it all reacts at a molecular level. I guess it could cause it to start breaking down earlier. I have no signs of degradation of my RX super 15W40 that i run in my 743 after 2 years, i haven't put a lot of hours on it, but it has a few plus time and its as good as the day i filled it up. When the oil is still in the ground in the form of crude oil, its under a lot more than 5,000 PSI.
I do like the idea of fire-resistant additives though.

 

[jklingel]

After this, i can see the whole "can of worms" starting
Will be interesting to see if we can actually get the *rite* answer for all this.
When you say engine oil is only made to withstand 200 psi or so, what difference is there between that and hydraulic oil? I just can't see any difference as they are both liquid so they can be compressed essentially indefinitely. I just don't understand how it all reacts at a molecular level. I guess it could cause it to start breaking down earlier. I have no signs of degradation of my RX super 15W40 that i run in my 743 after 2 years, i haven't put a lot of hours on it, but it has a few plus time and its as good as the day i filled it up. When the oil is still in the ground in the form of crude oil, its under a lot more than 5,000 PSI.
I do like the idea of fire-resistant additives though.

Tazza: I have a response to a few points you made. Nope, I ain't a petrol engineer, either. "When you say engine oil is only made to withstand 200 psi or so, what difference is there between that and hydraulic oil?" •• If hydraulic oil is made to withstand high pressure, then I'd have to assume there is a reason for that. I only know enough chem/physics to know that pressure (and some heat) can do weird things to media, as was mentioned above about oil going through tiny places under pressure. Too, my wife sure prefers the pressurized carbon on her ring finger, compared to carbon buildup on an engine. "I just can't see any difference as they are both liquid so they can be compressed essentially indefinitely." •• To the contrary, I believe. I doubt that under the pressures of which we speak you can compress oil measurably. That is why huge oil storage tanks are (at least were) tested full of water; when they burst, nothing much happened as the water was compressed zilch and so it "re-expanded" zilch. Air, on the other hand, well, we know what happens when a tire blows, etc. And, that's why we use oil to push pistons in cylinders. "I just don't understand how it all reacts at a molecular level." •• Neither do I, so I will have to trust the oil experts on this one. I'm surprised to read that, apparently, engine oil is advised in some owner's manuals. I find that interesting, but I can't see how it could be as good as hydraulic oil. That is just a "gut", though. "I guess it could cause it to start breaking down earlier. I have no signs of degradation of my RX super 15W40 that i run in my 743 after 2 years..." •• My dad worked for Standard Oil of Ohio, in the testing lab, for years, and he always told me that you can't often see much going on in oil, or see differences between oils, but your engine sure can. Hey, if I can't trust Pops, who can I trust? "When the oil is still in the ground in the form of crude oil, its under a lot more than 5,000 PSI." •• Yes, but crude has not gone through a cat cracker (or whatever is used now) yet, and the pressure is part of what MAKES it crude oil, so naturally pressure can't "hurt" crude. But once crude is cracked, all bets are off. EX: What happens to diesel fuel when it is compressed in an engine? That is my perspective on the issue, anyway.

 

[mllud]

Tazza: I have a response to a few points you made. Nope, I ain't a petrol engineer, either. "When you say engine oil is only made to withstand 200 psi or so, what difference is there between that and hydraulic oil?" •• If hydraulic oil is made to withstand high pressure, then I'd have to assume there is a reason for that. I only know enough chem/physics to know that pressure (and some heat) can do weird things to media, as was mentioned above about oil going through tiny places under pressure. Too, my wife sure prefers the pressurized carbon on her ring finger, compared to carbon buildup on an engine. "I just can't see any difference as they are both liquid so they can be compressed essentially indefinitely." •• To the contrary, I believe. I doubt that under the pressures of which we speak you can compress oil measurably. That is why huge oil storage tanks are (at least were) tested full of water; when they burst, nothing much happened as the water was compressed zilch and so it "re-expanded" zilch. Air, on the other hand, well, we know what happens when a tire blows, etc. And, that's why we use oil to push pistons in cylinders. "I just don't understand how it all reacts at a molecular level." •• Neither do I, so I will have to trust the oil experts on this one. I'm surprised to read that, apparently, engine oil is advised in some owner's manuals. I find that interesting, but I can't see how it could be as good as hydraulic oil. That is just a "gut", though. "I guess it could cause it to start breaking down earlier. I have no signs of degradation of my RX super 15W40 that i run in my 743 after 2 years..." •• My dad worked for Standard Oil of Ohio, in the testing lab, for years, and he always told me that you can't often see much going on in oil, or see differences between oils, but your engine sure can. Hey, if I can't trust Pops, who can I trust? "When the oil is still in the ground in the form of crude oil, its under a lot more than 5,000 PSI." •• Yes, but crude has not gone through a cat cracker (or whatever is used now) yet, and the pressure is part of what MAKES it crude oil, so naturally pressure can't "hurt" crude. But once crude is cracked, all bets are off. EX: What happens to diesel fuel when it is compressed in an engine? That is my perspective on the issue, anyway.

New Holland Has sold their new loaders for years with engine oil in the hydraulic systems? I dont know enough about oil to debate thi issue. I dont think theres too much difference between a Bobcat hyd. sys. and a N.H. hyd. sys. I do trust the poeple that design them to give the right recomendation. Mike

 

[OldMachinist]

New Holland Has sold their new loaders for years with engine oil in the hydraulic systems? I dont know enough about oil to debate thi issue. I dont think theres too much difference between a Bobcat hyd. sys. and a N.H. hyd. sys. I do trust the poeple that design them to give the right recomendation. Mike

I think that Tazza is right that we'll probably never end this controversy on engine oil versus hydraulic oil and the following comments are my thoughts and experiences from being involved the design process that big businesses go thru for their products.

I sat on design review committees as a Certified Manufacturing Engineer (CME) for a large manufacturing company that I worked for and some of the things that went into the process were selling points, length of warranty and replacement parts. There were many other things to consider but these are the ones that I think deal with this issue.

First let explain what a CME is. It means that I took a course and passed a test to receive a certificate from the Society of Manufacturing Engineers (SME). So no I didn't get a college degree in engineering.

Now I don't know what went on when Bobcat designed their machines but I think that most large corporations follows some kind of similar review process. Bobcat used the one oil for all as a selling point for years on their machines. It goes like this the salesman tells the buyer you only have to have one kind of oil for this machine so your dumb employees can't screw up and put the wrong oil in. But what you have to remember that they probably tested it and found that engine oil worked long enough to get the machine out of warranty. That's where the replacement parts come in to play. Because big business loves to sell replacement parts and new equipment. They price replacement parts high to force the buyers to consider buying new equipment. We would take an off the shelf part that you could be bought anywhere and have the supplier make small changes so that you had to come back to us for it. It would be simple things like change the thread sizes or bolt pattern. Small changes like this didn't really affect the price we paid very much but we could charge what ever we wanted for repair parts because the suppliers could only sell them to us. And when the demand for the part dwindled the price would only go higher because even though we had to supply it for 7 years nothing said we had to stock it or how long we could make you wait for it. So we would go back to the supplier and have them quote making one or a small batch and pass along the cost plus the normal markup. Sometimes the lead-time would be several months to get repair parts. I'm not saying I agreed with this but it's just the way businesses look at things.

I know that I've gotten off on a tangent here but I'm just trying to show that just because they said engine oil would work in the hydraulic system doesn't mean that it's good for it. Like I said at the beginning these are just my thoughts and experiences and you can put whatever oil you want to in your machine but I will continue to use hydraulic oil in my hydraulics and engine oil in my engine.

I'm sure that all of you that have diesel engines use oil that is designed for diesels in it. So you must believe there's something different between what oils are designed for. You wouldn't think of putting hydraulic oil in your engine so why put engine oil in your hydraulics.

 

[mllud]

I think that Tazza is right that we'll probably never end this controversy on engine oil versus hydraulic oil and the following comments are my thoughts and experiences from being involved the design process that big businesses go thru for their products.

I sat on design review committees as a Certified Manufacturing Engineer (CME) for a large manufacturing company that I worked for and some of the things that went into the process were selling points, length of warranty and replacement parts. There were many other things to consider but these are the ones that I think deal with this issue.

First let explain what a CME is. It means that I took a course and passed a test to receive a certificate from the Society of Manufacturing Engineers (SME). So no I didn't get a college degree in engineering.

Now I don't know what went on when Bobcat designed their machines but I think that most large corporations follows some kind of similar review process. Bobcat used the one oil for all as a selling point for years on their machines. It goes like this the salesman tells the buyer you only have to have one kind of oil for this machine so your dumb employees can't screw up and put the wrong oil in. But what you have to remember that they probably tested it and found that engine oil worked long enough to get the machine out of warranty. That's where the replacement parts come in to play. Because big business loves to sell replacement parts and new equipment. They price replacement parts high to force the buyers to consider buying new equipment. We would take an off the shelf part that you could be bought anywhere and have the supplier make small changes so that you had to come back to us for it. It would be simple things like change the thread sizes or bolt pattern. Small changes like this didn't really affect the price we paid very much but we could charge what ever we wanted for repair parts because the suppliers could only sell them to us. And when the demand for the part dwindled the price would only go higher because even though we had to supply it for 7 years nothing said we had to stock it or how long we could make you wait for it. So we would go back to the supplier and have them quote making one or a small batch and pass along the cost plus the normal markup. Sometimes the lead-time would be several months to get repair parts. I'm not saying I agreed with this but it's just the way businesses look at things.

I know that I've gotten off on a tangent here but I'm just trying to show that just because they said engine oil would work in the hydraulic system doesn't mean that it's good for it. Like I said at the beginning these are just my thoughts and experiences and you can put whatever oil you want to in your machine but I will continue to use hydraulic oil in my hydraulics and engine oil in my engine.

I'm sure that all of you that have diesel engines use oil that is designed for diesels in it. So you must believe there's something different between what oils are designed for. You wouldn't think of putting hydraulic oil in your engine so why put engine oil in your hydraulics.

I believe what you are saying.When Chevy,Ford and Dodge built cars and trucks for years with places in the bodies of their vehicles that traped mud and road dirt. They knew it would rust thru in x years.They built cars long enough to know better. It was as simple as larger drain holes.They built in self destruction in x years.Build it too good and you may not stay in bussines. Mike

 

[jklingel]

I believe what you are saying.When Chevy,Ford and Dodge built cars and trucks for years with places in the bodies of their vehicles that traped mud and road dirt. They knew it would rust thru in x years.They built cars long enough to know better. It was as simple as larger drain holes.They built in self destruction in x years.Build it too good and you may not stay in bussines. Mike

Oldmachinist: Thanks for that perspective, as depressing and disappointing as it is. As for trusting dealers, etc, let me relate this. I had trouble finding low viscosity oil for my Ford diesel, so I went to the dealer to see what they used. I specifically asked for diesel oil that had a CF-4 classification. The guy brought me a case of Pennzoil marked "for gas engines". When I apologized and said I apparently did not specify diesel, I got an "Oh, God, just buy this stuff" look and was told, quote, "This is what we put in every engine we change oil on. Period." I left the oil there and wrote to International. They sent me literature that clearly said "Under no circumstances should you use gas engine oil...", etc. I sent a copy to the dealer, and called 6 months later to see about scheduling an oil change. When I asked what oil they used, I was told "Whatever you bring." So, dealers may or may not know everything, and that just muddies the water for the consumer. No wonder we are all confused....

 

[mllud]

I believe what you are saying.When Chevy,Ford and Dodge built cars and trucks for years with places in the bodies of their vehicles that traped mud and road dirt. They knew it would rust thru in x years.They built cars long enough to know better. It was as simple as larger drain holes.They built in self destruction in x years.Build it too good and you may not stay in bussines. Mike

OldMachinist
By my previous post It looks like I missed the point you were about the manufacturer getting the machine past the point of liability before things starting failing. My point was more about built in self destruction.As a part time bodyman in the 70s and 80s I have to think they knew how long it would take for rust thru.I have an old N/H lx865. The pumps sound fair for about 3500 hours. I think when the pump start whinning Ill probably go with more viscosity with my oil. Do you think that might extend life a little or would that be a mistake. Mike

 

[Butters]

OldMachinist
By my previous post It looks like I missed the point you were about the manufacturer getting the machine past the point of liability before things starting failing. My point was more about built in self destruction.As a part time bodyman in the 70s and 80s I have to think they knew how long it would take for rust thru.I have an old N/H lx865. The pumps sound fair for about 3500 hours. I think when the pump start whinning Ill probably go with more viscosity with my oil. Do you think that might extend life a little or would that be a mistake. Mike

The origional question was switching to "motor oil". My manual from the company, not the dealer says to use "Bobcat Hydrostatic Fluid" or something of the sort and gives a part number. It goes on to say if you cannot get it use 10W-30.
I agree that modern motor oils have much more detergent than they used to and may not be the best option in a hydraulic system. If you read on a jug of Bobcat brand fluid, they have adsolutley no specs on there. However, I seriously doube that part of their corporate structure that has helped them grow for 50 years has been to plan for failure. It seems to me, that they use innovation as a selling tool rather than saying, your last one broke, so you need a new one. I would assume that Bobcat used some engineers when they designed their equipment and maintenance recommendations as well.