Hy-Guard VS JD 303 hydraulic fluid

[chriswheeler]

Hello all,
I'm getting ready to do my first winter service on my new to me JD 970. I notice, in the operators manual, that they call for Hy-Guard hyd fluid versus the JD 303 that I used in my old JD 950. I still have 4 gallons of new JD 303 left over in a bucket, is it compatible, interchangeable, or is it different stuff entirely requiring I go out and get something different. They go on to say in the Operators Manual that other oils that meet JDMJ20B can be used, what ever that is. This will be my first service cycle, doing all filters, oil and hydraulic fluid getting a fresh start for next spring. Thanks,
Chris

 

[jd110]

If I'm not mistaken, I think the 303 oil predates even your 950. I have worked for dealer since 1977 and Hygard was being sold then. I am thinking your oil has to be 35+ years old and it didn't have as good of anti chatter properties when it was new. Chances are good that even if stored in a sealed container it has probably absorbed moisture and impurities over the years. I would not recommend use in your 970 especially since it has wet brakes. Your 950 had dry brakes and oil wasn't as critical.

 

[Tx Jim]

jd110
IIRC 303 hyd oil was introduced in the Fall of 1960 with the introduction of the 10 series tractors. The hyd oil has been upgraded over the years to have more anti brake chatter inhibitors but I can't remember when Hy-Gard was introduced.

 

[greg_g]

JD303 is typically a 30 weight equivalent. HyGard is thinner, closer to 20W. Below that is Lo-Vis Hygard, down around 10W. I wonder if you could thin your 303 with some Lo-Vis and create a hybrid 20W HyGard?

//greg//

 

[chriswheeler]

This isn't old stuff, it's modern generic from big box stores that sells this stuff in 5 gallon pails around $40 per 5 gallons. From what I'm hearing here, the Hy-Guard has a different composition than the 303, different additives. Thinking about just giving the stuff to a neighbor that has a grey market Yanmar, going out and getting the
Hy-Guard, be done with it. I know this 970 uses a little more than the 950 used, will have to buy anyway. Guess the question was " are these interchangeable ?? " and looks like the answer is no. Thanks,
Chris