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Mike, that Deere power steering system is just a basic hydraulic system so power steering fluid, as well as trans fluid, motor oil, or hydraulic fluid will make it function.. The question is "for how long & how good?" ~A while ago I did a home brewed hot & cold oil viscosity tests of motor oils, hydraulic fluids & other hydraulic fluids & what I found was the closest for cold weather that stayed fairly close at high temps was good old standard Deere Hy-Guard.. Power steering fluid was ok at below 32°F but was way too thin at 80° up [that P/S fluid runs pretty hot when in operation]... ~At higher temps regular 10W40 motor oil was actually pretty close to the original Deere spec fluid.. In fact is was a real close match at 60°F & up.. Problem was it got way too thick at below 32°F.. ~Based on my O° to 140° unofficial viscosity flow tests I would say about the closest you will find to original Deere P/S fluid is Deere Hy-Guard.. ~If I get some extra time I plan on re-running my tests using some 10W40 & different synthetic motor oils as those might have better low temp flow characteristics & work out real good... I would really like to use a standard 10W40 motor oil as it has good anti foam, anti rust, & good high temp ability but it's thick viscosity at low temps could cause pump or pump drive shaft problems.. ~Based on my viscosity flow tests I believe the original Deere P/S fluid must be a mulit viscosity type engine oil with something added for better cold flowability.. JDClooney@aol.com
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