Oil & Fuel 80w in hydraulic?

mikeweber3 · Sep 22, 2011

I have a Kubota B7100 Serial B71001-59209 Manual transmission tractor. The hydraulics share the the tranny and rear end oil. My owners manual says "Use Gear Oil SAE No. 80 or equivalent" This doesn't make sense to me. do you think it is correct?

kuboman · Sep 22, 2011

mikeweber3 said:
I have a Kubota B7100 Serial B71001-59209 Manual transmission tractor. The hydraulics share the the tranny and rear end oil. My owners manual says "Use Gear Oil SAE No. 80 or equivalent" This doesn't make sense to me. do you think it is correct?

If you have a loader or any axillary hydraulics I would definitely use UHD. If not then use gear oil.

KennyV · Sep 22, 2011

a lot of the older Ford and Massey Ferguson tractors used 90 Wt gear oil in the hydraulic system... 3 pt had almost zero lift with anything lighter... KennyV

mikeweber3 · Sep 23, 2011

I do have a loader.

kuboman · Sep 23, 2011

mikeweber3 said:
I do have a loader.

If it was my machine I would use universal hydraulic fluid.:thumbsup:

MHarryE · Sep 23, 2011

Viscosity of 80W90 is not that far off UDT (I don't know if straight 80W is available anymore). It is about 15 cSt at 100ｰC. UDT is about 9 - 10 cSt at 100ｰC. At 40ｰ they are about 139 and 55. If you use UDT you are using a lighter weight oil than the gear lube although not by much, but you are losing the EP additives of gear oil. If your transmission needs the EP additives and you use an oil that doesn't have them, you will be looking at rapid wear and early failure. Unless you find out Kubota made a mistake in their manual, I would stick to their recommendation.

mikeweber3 · Sep 23, 2011

Thanks to all

I think I'll do 89/90.

kuboman · Sep 23, 2011

MHarryE said:
Viscosity of 80W90 is not that far off UDT (I don't know if straight 80W is available anymore). It is about 15 cSt at 100ｰC. UDT is about 9 - 10 cSt at 100ｰC. At 40ｰ they are about 139 and 55. If you use UDT you are using a lighter weight oil than the gear lube although not by much, but you are losing the EP additives of gear oil. If your transmission needs the EP additives and you use an oil that doesn't have them, you will be looking at rapid wear and early failure. Unless you find out Kubota made a mistake in their manual, I would stick to their recommendation.

There is not a modern tractor in use today that uses gear oil for hydraulics. Not one of mine uses gear oil, and they are putting 300hp through hypoid gears using transmission oil. Everybody can do as they please but if you don't want a sluggish loader I would use what Kubota uses now too.:thumbsup: