Komatsu PC09 travel motor oil?

[kiwibum]

I recently bought an old Komatsu PC09 mini excavator, I haven't owned an excavator before.

Looking at changing all the fluids before doing any more work with it after the first play, I was bewildered to see the service manual states SAE30 engine oil for the travel (track) motors (it also recommends SAE 10W-30 engine oil for the hydraulic system!)

Anyone on here service mini excavators, or know enough about 1ton excavators, can tell me why I shouldn't be using 80-90 gear oil rather than SAE30 engine oil?

Everything I've read about the reduction gears in the travel motors on excavators say they require a high pressure gear oil with a high viscosity.

From what I can tell the reduction drive gears in the PC09 are the same type as in larger excavators, just a smaller version.

 

[Nige]

why I shouldn't be using 80-90 gear oil rather than SAE30 engine oil?

Be aware that engine oil and gear oil are measured on different viscosity scales by the SAE. An SAE 90 gear oil is about the same viscosity-wise as an SAE 50 oil measured on the engine oil scale.

If it was mine it would get 10W-30 or 15W-40 in the engine, SAE 10W hydraulic or TO-4 oil in the hyd system, and an SAE 50 TO-4 oil in the final drives - but that’s because I’m a Cat guy and I’m more familiar with TO-4 oils.

Also bear in mind that oil performance has advanced tremendously since that machine was built and what’s available today is far better in terms of quality and performance. Of course the recommended lubricants chart has not changed in all that time and does not reflect today’s custom & practice.

 

[kiwibum]

Thank you Nige. I didn't know gear oil was on a different scale to engine oils, I assumed all oils where measured the same.

Machine has done 2700 hours. I had some 80W-90 gear oil and had put that in before I saw your reply. It only holds 330ml per side so not a big deal to change to lighter oil. The local car parts place only has gear oils either 75w-85 or 80W-90, so I'll have to look somewhere that specializes in machinery oils.

I have to replace the track roller and idler bearings first before I use the machine, so no rush to find the right oil, at least it has new clean oil in there.

Thanks again for your help.

 

[kiwibum]

I found a Comparative Oil Viscosity Chart, it shows SAE30 engine oil is between 80w-85w gear oil, so I'm thinking I will be fine with the 80W-90 I have in there. I'll need to find an oil specialist to confirm.

 

[Nige]

I think you’ll be just fine with the 80W-90 gear oil in the travel motors. I assumed you were starting from scratch and didn’t have oil so you were looking for recommendations of what to use.

 

[Nige]

This is the viscosity comparison chart I usually use. It also has conversions to ISO & AGMA viscosity ratings on it.

 

[kiwibum]

I was starting from scratch and looking for recommendations and yours were really helpful thank you. I realised I had a liter of 80w-90 left over from doing a diff some time ago and decided to use that since I was running out of time to move machine.

Good to know the 80w-90 will be fine. Yes that is the same chart I saw.

Thanks again for your replies and help, much appreciated.