5w-40 Mobil Syn in 790 JD

[Chuck-KY]

I am getting ready to service my JD 790 @ 150 hrs. I have followed threads here and read my owners manual untill I'm totally confused. Mobil states that it's Turo Diesel 5W-40 is fine to use in place of 10W-40 and I like the ideal of the lower weight oil for cold startups. My manual about lists every weight possible under certain conditions, kind of confusing for my simple mind. The dealer advises JD oil naturally, but I like the ideal of Mobil synthetic for no more than it really cost for my once a year oil change. I'm not trying to start an argument over syn. verses dino oils , or JD verses Mobil. I'm just alittle clouded over the issue and don't mind spending a few more dollars if the Mobil syn. is really better. I only put 50-60 hrs. a year on my tractor. I'm sure it has been beat to death, but please be kind and help me out here if you can about the validity of Mobil Turbo Diesel syn. 5W-40 in my 790 if you will. Thanks in advance for any advise - Chuck

 

[crashz]

The manual gives different options in oil viscosities based upon ambient temperatures. For colder temps, a lighter oil will suffice and provide adequate lubrication and not starve the engine during the first few cold minutes of operation. For hot operation, the hot viscosity needs to be within range to provide proper oil pressure and ( static and dynamic) film thickness.

A good 5w-40 like the Mobil 1 is great as a year round oil because its cold pumpablility is superior to conventional 15w-40 and yet can handle high heat stresses due to its higher warm viscosity than a typical 10w-30. Not only that but its a good oil and as far as I know it was still a PAO based oil as of a couple years ago. I wouldn't hesitate to run it in my tractor.

 

[amigauser]

I agree. That is what I run in my Kubota B3030. I also change my oil/filter once a year and that is around 50 hours a year like you. I get mine at the local Advance Auto Parts.

 

[RWEST]

If it has a Yanmar engine, either Mobil 1 TDT 5-40; Shell RTS 5-40 or J-D's own 0W-40 is the cat's whiskers.

 

[Chuck-KY]

I appreciate the good information and replies. The engine is the Yanmar. I think I will go ahead with the Mobil Turbo Diesel Truck 5W-40. I thought it seemed a good year round choice for a once a year oil change. Thanks again- Chuck

 

[RalphVa]

The temperature chart on my 4010 owner's manual says 5w30 works the entire range. That's what I used until this year. Switched to 0w30 Mobil 1 for even better protection year round.

The 1st number in the xwxx is the vis at low startup temperatures (typically 0 F used, or thereabouts). The 2nd number is represents the vis at operating temperature (actually 212 F, which is pretty close). It's a misconception that a 0w30 will not give the same protection (e.g. viscosity) at operating temperature as a 5w30. Absolutely not true.

I've 0w30 in all my engines now except for about a 50/50 mix of 5w40 and 0w30 in the old Benz, because I had some leftover 5w40.

They all sound smoother at startup now. In particular, the VW (only one with hydraulic valve lifters) doesn't "pound" the lifters at startup now due to now enough oil in them at startup.

Ralph

 

[RalphVa]

Further thoughts on comparing 5w30 to 0w30 (or 15w40 vs. 5w40). The one with the smallest 1st number will actually be HEAVIER at operating temperatures greater than 212 F, which could be the case in certain areas of the engine. My current 0w30 will be HEAVIER than a 5w30 at an operating temperature of say 300 F, like on the cylinder walls. This all has to do with the response of viscosity to temperature: inverse and on a log log scale, approximately. The 0w30 will be lighter and easier to pump at startup temperatures.

Ralph

 

[Shimon]

The one with the smallest 1st number will actually be HEAVIER at operating temperatures greater than 212 F

I've never heard this one. Can we have a little more detail regarding this statement? I see what you are saying but as far as I know, the second number in multi-grade oils is the viscosity at 212F (the amount of time it takes a standard amount of oil to flow through a standard sized hole at standard temperature). And I know that as temperature increases, the viscosity decreases logarithmically.

What I don't understand is how two different multi-grades (0W30 and 10W30, for instance) can have different viscosities at 212F. Does the SAE 30 rating have a range and the 0W30 sit higher in the range than the 10W30? Is that what you are saying? Or are you saying as the temperature rises above 212F the two oils will start to show different viscosities? Because if this last statement is true...I would like to see the log scales for both oils (I searched the net but couldn't find any scales). I'm no math wiz but I would think that the log scales should fall off quicker for the 0W than the 10W oil. I would have to see the numbers to be a believer.

Also, I also thought that in order to gain the larger differential between the winter rating and the 212F rating you had to use more viscosity modifiers which meant less "oil". So, a 0W30 oil would have less volume of "oil" because it needs more viscosity modifiers than a 10W30 oil. I'm sure it's on a very small scale and maybe it doesn't make much of a difference at all, but that is one of the downsides that I'm aware of for oils with a lower winter rating.

Any references would be nice too. Not that I don't believe you...but I like to see references on a forum because there is a lot of bad info flying around (no offense to anyone). Please educate me.

 

[DieselPower]

Oil Viscosity: Technically, the viscosity of an oil is a measure of the oil’s resistance to shear. Viscosity is more commonly known as resistance to flow. If a lubricating oil is considered as a series of fluid layers superimposed on each other, the viscosity of the oil is a measure of the resistance to flow between the individual layers. A high viscosity implies a high resistance to flow while a low viscosity indicates a low resistance to flow. Viscosity varies inversely with temperature. Viscosity is also affected by pressure; higher pressure causes the viscosity to increase, and subsequently the load-carrying capacity of the oil also increases. This property enables use of thin oils to lubricate heavy machinery. The loadcarrying capacity also increases as operating speed of the lubricated machinery is increased. Two methods for measuring viscosity are commonly employed: shear and time.

Shear: When viscosity is determined by directly measuring shear stress and shear rate, it is expressed in centipoise (cP) and is referred to as the absolute or dynamic viscosity. In the oil industry, it is more common to use kinematic viscosity, which is the absolute viscosity divided by the density of the oil being tested. Kinematic viscosity is expressed in centistokes (cSt). Viscosity in centistokes is conventionally given at two standard temperatures: 40°C and 100°C (104°F and 212°F ).

Time: Another method used to determine oil viscosity measures the time required for an oil sample to flow through a standard orifice at a standard temperature. Viscosity is then expressed in SUS (Saybolt Universal Seconds). SUS viscosities are also conventionally given at two standard temperatures: 37°C and 98°C (100°F and 210°F). As previously noted, the units of viscosity can be expressed as centipoise (cP), centistokes (cST), or Saybolt Universal Seconds (SUS), depending on the actual test method used to measure the viscosity.

Viscosity index: The viscosity index, commonly designated VI, is an arbitrary numbering scale that indicates the changes in oil viscosity with changes in temperature. Viscosity index can be classified as follows: low VI - below 35; medium VI - 35 to 80; high VI - 80 to 110; very high VI - above 110. A high viscosity index indicates small oil viscosity changes with temperature. A low viscosity index indicates high viscosity changes with temperature. Therefore, a fluid that has a high viscosity index can be expected to undergo very little change in viscosity with temperature extremes and is considered to have a stable viscosity. A fluid with a low viscosity index can be expected to undergo a significant change in viscosity as the temperature fluctuates. For a given temperature range, say -18 to 370°C ( 0 - 100°F), the viscosity of one oil may change considerably more than another. An oil with a VI of 95 to 100 would change less than one with a VI of 80. Knowing the viscosity index of an oil is crucial when selecting a lubricant for an application, and is especially critical in extremely hot or cold climates. Failure to use an oil with the proper viscosity index when temperature extremes are expected may result in poor lubrication and equipment failure. Typically, paraffinic oils are rated at 38°C ( 100°F) and naphthenic oils are rated at -18°C (0°F). Proper selection of petroleum stocks and additives can produce oils with a very good VI.

 

[sixdogs]

Go away from the viscosity issue for a moment (guys here are brilliant on that stuff) and be concerned about the "zinc" or "phophorus" issues currently discussed reagrding valve train wear and lubricity of the oil. It will eventually matter to all of us.

I can't recall the numbers exactly but believe Mobil 5W40 has enough "zinc" to be OK. I used this last time in my JD 790 and would not have used if suspect. Find previous threads to learn more about "zinc".

However, I recently learned that JD 0W40 synthetic has more "zinc" --and was a better price--than the Mobil One so I am switching back to the JD Syn.
Of note, the JD container may say it is "semi" syn but it is really full synthetic and will state so when they run out of the old packaging. Search for those threads as well. It's full syn.
I run JD 0W40 in my bigger equipment and love the cold-start and instant lube issues. It works for me and it comes in a 5 gallon container.
I think both are OK but one is or might be better and cheaper. Just my two cents.