(STOU) or a dedicated Hydraulic oil ISO VG 32/46 for the Backhoe?

Agrol Kombi Classic (STOU) or a dedicated Hydraulic oil ISO VG 32/46

Question:
I find it surprising often seeing the recommendation of using the thinner winter type ISO VG 32 hydraulic oil over the normal ISO VG 46 for such a rather unsophisticated agriculture implement as a backhoe. The hydraulic system of these Chinese made backhoes are equipped with a rather small pump CBN-E310 model with only 20 liter/min flow. Paired with a quite small hydraulic oil reservoar and generally small dimensioned hoses of the backhoe, increasing the flow of the pump (in isolation) is a bad idea, which we experienced last year. Cavitation problems with the oil heated up as the result, that would have worsened further if we also were using a thinner ISO VG 32 oil. Maybe if we reconsider digging in the winter time, we could think about replacing the ISO VG 46 with ISO VG 32 oil.

At the same time as revisioning our Three Point Backhoe with a new pump and larger hoses for better flow, we are also moving to a dedicated hydraulic oil, but only for the backhoe cistern.

Currently, the entire tractor and backhoe have been using a STOU oil. But after recommendations from our local oil company, I understand we'll get a prestanda improvement of the backhoe, especially at lower temperatures, if changing to a dedicated hydraulic oil (ISO VG 32/46).

Since we are not using the backhoe in winter times, I think it would be just silly of us to use the thinner ISO VG 32 viscosity. Especially, since there is a general rule of thumb, that it's always better with using a higher viscosity than too low dito. (However, some machines may need ISO VG 32 for a good function at low temperatures.)

For our backhoe, we therefore decided on ISO VG 46 from now on.

ISO VG class            SHS 32   SHS 46    SHS 68     STOU    
Viskositet        40°C     32.7     46.9       68.8       71.0   mm²/s
Viskositet       100°C      7.5       9.4       11.9       11.2   mm²/s
Viskositet       -20°C        —       1750      4800      2900   mm²/s
Viskositet       -30°C     3600    7800         —        —      mm²/s
Viskositetsindex             208       190      170       149             
Temperature range for classes of hydrulic oil according to SIS:
(The ISO VG class numbers corresponds to viscosity in cSt @ +40ºC).
(ISO VG 32 hydraulic oil corresponds to motor oil viscosity SAE 10W,
ISO VG 46 hydraulic oil corresponds to motor oil viscosity SAE 20).

SH 15    -29ºC – +50ºC
SHS 32  -25ºC – +75ºC
SHS 46  -15ºC – +90ºC 
SH 68      -5ºC – +90ºC
 

APPENDIX: (from another tractor forum)

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Choosing the best oil for the Chinese made Tractor & Backhoe

We have a Chinese Foton FT404 tractor, that takes: STOU 10W/30 GL-4 (equiv. SAE80W transmission oil):

• Engine sump 7 l (API CD)
• Gearbox 27 l (MF1135, M2C 86A, JD J20A)
• Front axle 7 l (MF1135, M2C 86A, JD J20A)
• Lifter 12 l (UTTO for hydraulics)
• Steering 0.8 l (UTTO for hydraulics)

I would recommend what our dealer already has put into the tractor at the delivery, Agrol Kombi Classic (name changed from Turbo Kombi), a STOU oil. Similarly we can use Statoil MultiWay or OKQ8 T1000, all 10W-30. We can also use Biltema Tractor Oil Universal, Kombiolja 10W-30 at 299 SEK for 10 liter.

In the FOTON user's manual, the requirement for oil is separated for the engine (MOTOR) and for the transmission/hydraulics (UTTO). These STOU oil recommendations above exceeds the requirements for the tractor. Both the low cost and the handling of a single oil bought in large quantities (10 or 20 liter) makes STOU a given for these 1980-decade of tractor technology.

That's what we practise with our Foton FT404, and it also came with Agrol Turbo Kombi oil in all reservoars. It worked well during the Nordic cold winter period as well.

We have also found Baldwin equivalents for the fuel & lube filters:
Clarcor Filtration: WBF7608 -> Baldwin BF7608
Clarcor Filtration: WB202C -> Baldwin B7451

*)
STOU = (SUPER TRACTOR OIL UNIVERSAL)
UTTO = (UNIVERSAL TRACTOR TRANSMISSION OIL)

Ref:

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