Motor oil used in hydraulic system

[The Danes Are Coming]

In or around May 2009 we had a thread relating to hydraulic systems. The thread is apparently so old that the system will not allow me to add a reply, so I have had to reopen this issue in a new thread.

Here is a link to the old thread.

Just to recap:

Quote:

Originally Posted by The Danes Are Coming I hope that I am right Bill or I may have done some damage last time I refilled the reservoir. On page 220 in my manual it reads: "............The reservoir is filled with 15W-40 motor oil from the factory.........." Then follows the filter specifications. I have a PDF copy of my manual on my private web site. Check it out and look up page 220. I have to admit that I was baffled also when I first saw the use of motor oil in a hydraulic reservoir but since this was listed so specific I assumed that this was not a mistake.

I am bringing this up again since we are about to return to the US and therefore now have the chance to address the problem (if it is a problem). In the meantime Monaco is also back in business and their tech support is operating.

I have now contacted Monaco's tech service per e-mail:

My question:

In section 10 on page 220 in my 2007 Diplomat owners manual the power steering reservoir with internal filter is described. 7 lines down it states "The reservoir is filled with 15W-40 motor oil from the factory". Is this misprint? Is it filled with motor oil and if so, why is it not filled with hydraulic oil. IMPORTANT: If it is a misprint I really would like to know fast, since I have just topped up my system with motor oil as specified. Have I done this wrong and if I have, what should I do about it? Please specify the correct type of hydraulic oil if this is what is needed.

Monaco answer (and this is the entire answer):

We do use 15-40 hydraulic oil it is almost clear

My reply:

You didn’t answer my questions:

1: Is it a misprint in the manual: Yes/No

2. Now that I have re-filled with motor oil, what do I do about this?

3: I have now Googled 15-40 Hydraulic Oil and nothing comes up. Is hydraulic oil graded the same way as motor oil?

You need to be more specific in you reply. Please address all my questions.

Monaco reply (and again this is the entire answer):

It is motor oil since about 2003 we have used motor oil in this application for the Diplomat and Endeavor hope that makes sense.


My conclusion:

Although the Monaco answer, to me, is not all that convincing, I will have to rely on that my 2007 Diplomat hydraulic reservoir is indeed filled with motor oil. This will therefore also apply to some of your rigs which is the reason that I am now starting this new thread.

We are now all confused at a much higher level than before - well, at least I am.

[duramax]

I read the old thread and have to agree with Jim Stewart that you should remove the oil and flush the reservoir with clean Dextron III. Empty the reservoir and refill the system again. Remember that the viscosity spec. for the motor oil states 15W-40, which means that when the oil is cold it is 15 weight but when it heats up it is at a viscosity of 40 weight. The system may not perform correctly with that weight oil. True it is diluted but I wouldn't take a chance by leaving it in the system.

[The Danes Are Coming]

Hi Carl and thank you for your reply.

I need to make sure that I understand the reason for your suggestion. Are you saying:

1) that Monaco made a wrong choice by filling all Diplomats since 2003 with motor oil in the hydraulic reservoir, or are you saying
2) you don't believe that I have been given the right information, and that it is in fact hydraulic fluid that is in my reservoir?

If the information I was given is correct, why would I want to flush out the system and then add a fluid that is different to what the manufacturer used in the first place?

[walt2137]

Dane there was 3 different fluids used over the yrs by Monaco, AW46 hyd fluid (clear), Dexron trans fluid (red), and engine oil 10w40 (yellow) and all will work ok and do no damage to the seals. If it was me I would change the filter and add ether 10w40 or dexron to refill and not worry about flushing the system. I would have no problem mixing dexron in the hyd system with 10w40 as it is not going to hurt anything. If you are in the north and the steering is sluggish because of the cold then I would go to the 10 wt oil, Dexron or AW46. I had dexron in our old dip and have AW46 in the dynasty.

[jckc779]

I found this thread 3 days too late! I just replaced the hydraulic filter and needed to add a little fluid. My manual (2003 Diplomat) says the fluid is Dexron III. The fluid clearly looked and felt like motor oil. I ended up draining it and refilling with the Dexron thinking the fluid was so old and contaminated that it didn't look right anymore. Glad to hear I'm not completely crazy.

[Happycarz]

I agree with Walt. I had a 93 Dynasty that came with ATF. In the summer it was hard to turn when not moving. Monaco told me to replace the ATF with 15w-40 and that cured it.

Henrick, just keep it topped off with 15w-50 motor oil. Don't worry about mixing or draining/flushing the fluid. This is a non issue. Get out of the cold and enjoy Texas.

[The Danes Are Coming]

Mystery solved - I am no longer confused.

Thanks all !!!

[duramax]

1) that Monaco made a wrong choice by filling all Diplomats since 2003 with motor oil in the hydraulic reservoir, or are you saying
2) you don't believe that I have been given the right information, and that it is in fact hydraulic fluid that is in my reservoir?

I am not saying either of those things, I am not sure that mixing oils is a proper thing to do as the chemical composition of them is slightly different and residue and sludging could possibly result. However based upon the follow up emails from Walt and Happycarz perhaps their advice is best.

[walt2137]

No Carl I wasn't saying ether, I was just saying what I would do and that mixing engine oil and Dexron wont create slug or hurt anything in the hyd system.
Sorry you took my statement personal.

[wa8yxm]

One of the harshest services for hydraulics would have to be, in my not very humble opinion, valve lifters.. These little pistons take a pounding hundreds of times a minute as the engine turns (At 2,000 RPM it's 1,000 Poundings per mintue) and the hydraulic fluid in them is..... Motor oil.

So it's not surprising.. And in fact it makes sense.. One less product to inventory for the factory.. One less product for you to lug around with you "just in case"

[lapalma-xl]

hello, great site im a new to motorhome and we just bought our 1st motorhome. when i check the resevoir for power steering its low so when i check the manual it states to use 15w 40 motor oil but when i check my reservoir its in yellow color and smells like power steering fluid. so after reading this thread i am now very confused what to use to fill it. will it damage if i mix the 2? 15w 40 and dex 3 fluid? please help. thanks

[The Danes Are Coming]

Hi LaPalma-XL

Welcome to this forum. This is the best place for information without a doubt.

The reply I eventually got from Monaco was that they did use engine oil since 2003 in the Diplomat and the Endeavor (they didn't mention the la palma). If your manual reads "motor oil" I would be inclined to think that this is what is in your La Palma, but to be on the safe side you could call or write Monaco's tech boy's. Better to be safe than sorry.

e-mail mcctech@monacocoach.com
Phone 877-4-MONACO

[walt2137]

Quote:

Originally Posted by lapalma-xl hello, great site im a new to motorhome and we just bought our 1st motorhome. when i check the resevoir for power steering its low so when i check the manual it states to use 15w 40 motor oil but when i check my reservoir its in yellow color and smells like power steering fluid. so after reading this thread i am now very confused what to use to fill it. will it damage if i mix the 2? 15w 40 and dex 3 fluid? please help. thanks

If it yellow in color then its not Dexron III and Dane is right Monaco did use 15/40 w and I think that is what you would have , they also used Dexron III and AW 46 just to keep us confused

[lapalma-xl]

thanks for reply. i talked to my mechanic and the service tech where i bought my motorhome and they say to just use power steering fluid and also i can use dex 3 ATF as well. and it will not harm if i mix the 2 so i just filled it with power steering fluid. hope this all good.