Frank McElroy Posted February 12 Share Posted February 12 2 hours ago, Jetjockey said: I was surprised to read here that aw46 oil expands as it gets colder. I thought the viscosity increased as oil cooled and that expands at a rate of about 4% of volume per 100 degrees Fahrenheit as it heats. Transmissions and some other components are checked with oil at operating temperatures so the systems are not overfilled when checked on a cold reading. Anyone know for sure. The problem has nothing to do with AW46 expanding as it gets colder - it doesn't. The issue has to do with viscosity. Monaco experience showed a high frequency of hydraulic oil cooler failures when temp get very low - teens, single digits or below zero DF. The high pressure from very viscous AW46 hydraulic fluid, when operating under very cold conditions, was the reason for the hydraulic heat exchanger failures. That's why Monaco changed over to using transmission fluid instead of the cheaper AW46 hydraulic fluid. 2 1 Link to comment Share on other sites More sharing options...
Jetjockey Posted February 12 Share Posted February 12 Thankyou frank. Short sweet and to the point. I could not locate any information telling of expansion. Our machines operate in very cold temperatures due to hungry livestock. 10w or less viscous hydraulic oils are used in a closed center hydraulics so the oil and machine can warm up some before a demand is made on the hydraulic pump. The end. Link to comment Share on other sites More sharing options...
Frank McElroy Posted February 13 Share Posted February 13 Glad I could shed more information on the topic. With oil, it's all about high viscosity at low sub freezing temperatures being the problem, and even though heat exchangers are on the low pressure side, with the high oil viscosity they can damage heat exchangers as Monaco found out. Tom Cherry, thanks for editing your original post to correct the issue from being an oil expansion issue to a high viscosity issue causing heat exchanger failures. Bottom line, if you are traveling in very cold weather conditions, use ATF and not AW46 as your hydraulic fluid. 1 1 Link to comment Share on other sites More sharing options...
Georgia Mike Posted February 13 Author Share Posted February 13 5 hours ago, Frank McElroy said: Bottom line, if you are traveling in very cold weather conditions, use ATF and not AW46 as your hydraulic fluid. Thanks for all the information from everyone. I’m going to change to ATF when I get back because we do and have traveled in some areas where I started up in the morning in the 20’s and I’m also not worried about mixing the two anymore. 1 Link to comment Share on other sites More sharing options...
Tom Cherry Posted February 13 Share Posted February 13 1 hour ago, Georgia Mike said: Thanks for all the information from everyone. I’m going to change to ATF when I get back because we do and have traveled in some areas where I started up in the morning in the 20’s and I’m also not worried about mixing the two anymore. Sounds like a plan to me. I had ATF and just drained my small reservoir and replaced with Transynd….twice…and plan no further service, unless I wake up one morning and am “wearing a younger man’s clothes”….to paraphrase Billy Joel. In your case, I’d probably drain the oil and get rid of the bulk of it….no flush….but then use Trransynd or Mobil Delvac. But if all I did was drain the large reservoir, I’d get a name brand ATF and not worry. But, i’d do that one more time circa 2029….and then probably never service again… BTW. I might compare the cost of a non synthetic name brand ATF to the Mobil ONE (1) and would seriously consider using the Mobil ONE….BUT THAT IS ME….not you. Either way, you’ll be ahead….and not at risk for the dreaded “VISCOSITY TRANSFORMATION”… LOL 1 Link to comment Share on other sites More sharing options...
Jetjockey Posted February 13 Share Posted February 13 If you have aw46 and want to lower its viscosity some you could add aw32. I read it is commonly done to deal with colder temps. May not be necessary for you . Link to comment Share on other sites More sharing options...
Kenster Posted February 14 Share Posted February 14 On 2/10/2024 at 8:18 AM, 96 EVO said: Don't know if you have read any previous threads on this subject, but, Monaco was 'all over the map' on what their manuals said was installed, and what was actually installed. Could be ATF, Hyd fluid, or engine oil! I even had one of their tech support tell me they would 'occasionally' add red dye to hyd fluid, before filling! Like Jim said, you may be better off draining and starting over with fresh ATF! Transmission fluid will be pinkish red, while hydraulic fluid will be a clear to yellowish color, and engine oil Black slash bluish in color. Link to comment Share on other sites More sharing options...
jimg_vls Posted February 14 Share Posted February 14 If an oil man would respond, atf is 10 weight very high detergent, most hydraulic oils are 10 weight. ATF is just a very high detergent oil. Link to comment Share on other sites More sharing options...
Tom Cherry Posted February 14 Share Posted February 14 2 hours ago, jimg_vls said: If an oil man would respond, atf is 10 weight very high detergent, most hydraulic oils are 10 weight. ATF is just a very high detergent oil. @Frank McElroy I believe someone just rattled your cage, an an "OIL MAN"...or maybe a SENIOR OIL MAN....Can you respond....this it getting "heady"... LOL Link to comment Share on other sites More sharing options...
Tom Cherry Posted February 15 Share Posted February 15 On 2/14/2024 at 2:31 PM, Tom Cherry said: @Frank McElroy I believe someone just rattled your cage, an an "OIL MAN"...or maybe a SENIOR OIL MAN....Can you respond....this it getting "heady"... LOL Frank McElroy, our resident Oil Man member, sent me a response and asked me to post it. As an aside, Google is your friend for many "layman's explanations" and you can learn a lot...but Frank says... I don't see the mind game debate on this topic. If someone wants to toss around numbers saying that ATF is 10 weight oil, I revert back to - In God We Trust - all others bring data. So, here are the data on AW32 vs 46 vs 68. Let's add in Dexron. For Dexron, the viscosity numbers for -40, 40, and 100DC are 11500, 29, and 6.0 respectively. Much a bit lower than AW32 and much lower than AW46. We need REAL data for a discussion or debate…. BTW, numbers for -40, 40, 100dc for Transynd are 8500, 38, and 7.4 respectively OK….thats how an Oil Man understands and responded. NOW... the original question was "MIXING". has been really beat to death.....However, the comment that "all are the same" is incorrect. Please google if you need additional information. On occasion, the moderating staff will provide technical or practical information so that there is no misunderstanding.... That is the case here. End of discussion…. Now the rest is for anyone that is interested and the history....as this comes up at least twice or more per year. In the future, we will reference this topic for information... So read on or not.... This is the WHOLE SAGA….and it fills in a lot of blanks that many do not know as well as the history…. Motor Oil is a lubricant. It has a lower flash point. It is designed and formulated to be used for lubrication, primarily in internal combustion engines. It is NOT a Hydraulic Fluid and was never intended to be used or substituted for same. Hydraulic Fluid is a generic name for two (or maybe more) types. Hydraulic Oil or the original specifically formulated fluid was designed for use in Hydraulic applications. Typically in pumps and cylinders and such. It is approved for use in the Steering Sectors (our Power Steering system) in our Motor Homes. TRW and Shepherd make them. They both approved the use of a "Hydraulic Oil". Our Pumps are also approved for Hydraulic Oil....as is the Hydraulic Motors used on some Motor Homes to circulate or drive air across the Side Mounted Radiator clusters. Automatic Transmission Fluid is a "lighter weight" Hydraulic Fluid that was designed for use in an Automatic Transmissions and other applications. MOST of the Hydraulic Slide systems we have specify ATF or a vendor's fluid such as the HWH fluid. Again, if you GOOGLE "Difference between ATF and Hydraulic Oil", there are many short explanations as well as technical papers. Monaco originally used AW46 as the Hydraulic Fluid for the motor homes with and without side radiators and it was approved by TRW and Shepherd and the Pump and Fan Motor vendors for use in their equipment. It seemed like a logic choice. Over time, due to customer complaints as well as some massive or large $$ failures, Monaco migrated to ATF due to the issues. THAT WAS posted earlier. But Monaco was NOT consistent and sometimes their decisions were based on "what was on hand" or also NOT WELL RESEARCHED nor did they comply with a component manufacturer's requirements. In ONE specific year(s) when Monaco was in transition between AW46 and ATF, the Oregon facility, who was supposedly the "ENGINEERING" source, only used AW46 OR ATF. However, the Elkhart Facility used Motor Oil for the Hydraulic Fluid. One can research but based on conversations with TRW, that would not have been approved...or perhaps NOT RECOMMENDED. For those with the Motor Oil "Hydraulic Fluid", it is NOT recommended, I believe, for the steering sectors...but it has been used and we are NOT high mileage users... If it "Ain't Broke"...but one could convert and ATF would be the logical replacement. TRW, the steering sector preferred vender, decided to switch or perhaps UPGRADE from Hydraulic OIL to ATF in order to get improved life from their products. They specified the Allison Transynd as the required Hydraulic Fluid for their long life or high mileage warranty. This information was provided by an Allison Tech Support Engineer that had worked for Allison but was now a TRW employee. The LOGIC: Allison spent a virtual fortune developing the best Hydraulic Fluid for their transmissions. ATF worked and was approved for TRW products....but for long range life and minimum downtime, TRW decided to use the Allison Transynd rather than fund a massive research project. BOTTOM LINE. I had ATF and had bought AW46, per the manual. The Hydraulic Pump and Fan Motor Vender told me that "YES" you could mix...not advised...but it would work. TRW said the SAME thing....but added... If you have ATF, then they would scrap the pail of AW46 and then replenish or switch over to Transynd and the life expectancy of their steering sector, as well as the pump and fan motor would be greatly increased. That is what I did. 1 1 Link to comment Share on other sites More sharing options...
Solution Frank McElroy Posted February 16 Solution Share Posted February 16 Tom - As a follow-up to our discussions, thank you for posting my offline comments. Bottom line - if you are starting the engine or driving in very cold climates (teens DF or below) use ATF or Transynd and NOT AW46. Your hydraulic oil cooler will thank you. 1 1 Link to comment Share on other sites More sharing options...
Gary Cole Posted February 16 Share Posted February 16 ATF fluid is not just a low viscosity oil. It must lubricate the metal components of the transmission while not being so slippery as to compromise the clutch band function. So compromises are made in the formulation. Some manufacturers have used Dexron in their air shift transmissions in order to facilitate shifting at cold temps at the expense of increased wear and noise level because not are operators could be trusted to take operating temps in consideration. Link to comment Share on other sites More sharing options...
dl_racing427 Posted February 16 Share Posted February 16 12 hours ago, Frank McElroy said: Tom - As a follow-up to our discussions, thank you for posting my offline comments. Bottom line - if you are starting the engine or driving in very cold climates (teens DF or below) use ATF or Transynd and NOT AW46. Your hydraulic oil cooler will thank you. Thank you Frank for the professional explanation and advice. This settles it for me. When I change my hydraulic fluid, it will be Transynd. Link to comment Share on other sites More sharing options...
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