1950 D4 7U Hyd OIl Type

Hello DanDawn 79; This is what Dad had us use in his older cats. In the engine SAE 30 Summer SAE 10 winter hyd SAE 10 transmission and final drives 90 wt gear lube later on 85-140. Always work well for us.

We have a 1949 D2 5U and use modern Hyd oil in our machine. After talking with our local Cat dealer they also reccomended using modern 15w40 engine lube oil and staying with 80w90 for the finals. As with all diesel engines when you add coolant be sure to check the DCA's (helps prevent cavitation damage to liners and water pump.) Our dealer has been a great source of help. Hope this helps and you have many hours of enjoyment with your new machine.

A month or two ago, a similiar thread showed up and went on for 2 pages about which oil to use.
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Type OIL in the search in the upper right hand of your screen, I'm sure you will find LOTS of interesting reading! 👍

Hello , I recently replaced some seals on the pump shaft of my D4 7U with no. 44 hydr.control . I also changed the filter , which can be had from Cat but at a high price . About the oil : I still had hydraulic oil (SAE10) in stock so I filled the system with this oil . But after the system reached some temperature the pump started a yelping sound every time I lifted the blade . Then I drained the system and filled up with 10W40 . The sound was completely gone even at high temperature . I know that in the past an SAE 30 was used but I don't know if this single grade oil is still available .
The Netherlands ,johan7