Proposal for 422 vs 425 shootout

[KentT]

I've just ordered Amsoil 20W-50 to put in my older PT 425. Being synthetic, the "20" shouldn't effect the starting that much, but I'm hoping the "50" when combined with other synthetic properties, will reduce the amount of torque loss when the oil gets hot... I find that with these old wheel motors, they perform fine when cold -- it's only when they're hot that they're marginal. According to the Amoil rep, it's likely due to "foaming" either in the pump (then going on through the circuits) or in the wheel motor (or both) that cause the problem. The tiny air bubbles then compress, instead of tranferring their "power" to the gears in the wheel motor. He thinks any sythetic should help, plus the slightly thicker oil (within reason, of course) will retain more of its initial "cold characteristics." He also pointed out that this foaming would likely not be visible in the holding tank... only when the oil was under high pressure.

I'll let you know my "seat of the pants" impressions when I get it put in and spend a few hours with it...

 

[SnowRidge]

Here is an interesting insight into automotive oil in a hydraulics application. Now, if I could just understand all of it.... /forums/images/graemlins/crazy.gif

 

[J_J]

I had read this years ago, and agree with what was said. Even though our manufacture [ PT ] recommends 10 W 30 for general use. I could get away with non detergent 30W oil here in Florida. Its the colder climates that would have trouble. That detergent oil keeps any water in the system in suspension, and makes it foam, which is not good. The water should go to the bottom in a perfect system.

 

[FOURTEEN]

<font color="blue"> (I haven't found a slope yet that my PT422 wont climb)
</font>

<font color="red"> But how well does it climb when you take it off the sidewalk??!!

</font>

 

[BAGTIC]

Don't mow directly 'uphill'. Do what farners do and mow on the contour (around the hill) beginning at the top and working downhill.

 

[cqaigy]

<font color="red"> But how well does it climb when you take it off the sidewalk??!! </font>

Oh ha ha very funny. how do you spell sarcasm? /forums/images/graemlins/grin.gif

 

[Marks481]

<font color="red"> But how well does it climb when you take it off the sidewalk??!!

</font> )</font>

Why would I want to do that? Then it would get dirty, and I wouldn't have time to "maintain it", because I would be spending all my time washing and waxing it like you do

 

[KentT]

</font><font color="blue" class="small">( Here is an interesting insight into automotive oil in a hydraulics application. Now, if I could just understand all of it.... /forums/images/graemlins/crazy.gif )</font>

Yes, I'd read that. The problem is that the only non-detergent oil that seems to be available is standard 30 weight. IMO, that's too thick for startup, and the viscosity at higher temps is really pretty low...

Supposedly, AMSOIL doesn't foam like the "dino oils" -- we'll see how it works.... I went with AMSOIL pure sythetic, since it's about the same price as Mobil 1's blended sythetic, and has a higher viscosity index... 169 unless I'm mistaken. It cost $212 and change for 10 gallons, delivered to the door.

Now, I have to get the two frayed steering hoses replaced before I put this "liquid gold" in the system...

 

[MuncyBob]

Is there a reason why you opted for motor oil as compared to actual hydro oil??

 

[KentT]

</font><font color="blue" class="small">( Is there a reason why you opted for motor oil as compared to actual hydro oil?? )</font>
I'm certainly no expert on oils, but after a bit of research I went with synthetic motor oil for three reasons:

1. The "known starting point" for the factory's recommendations was 10W40 based on the decals (or 10W30 based on the manual), so I wanted something I could compare to what came in it... Without knowing the specific brand of oil that comes in the PT, I couldn't find specific test results for it -- but I did have the "anecdotal evidence" that all sythetics seem to have better "cold starting" characteristics than regular multi-blend motor oils. So, thinking 20W synthetic might compare well (or at least not much worse) than 10W motor oil for cold starting, I focused on what handled heat the best...

2. Hydro oil is classified by different standards, ISO vs SAE, so it's hard to compare them "head to head." Typical hydro oils (for example, ISO 32 and 46) oil is supposedly somewhere between 10W and 20W, and is a "standard weight", not a multi-blend. Think of it like 20W or 30W standard motor oil, not 5W20 or 10W30, so it is thicker in cold weather starting conditions, and thinner when extremely hot than a multi-blend like 10W40.

3. The 20W50 synthetic motor oil actually has a MUCH higher viscosity at 40 degrees Celsius (104 degrees Fahrenheit) based on ASTM D-445 tests -- 126 versus 47.5 for ISO 46 hydraulic oil or 32.5 for ISO 32 (the most common hydraulic oils). AMSOIL's thickest hydraulic oil (ISO 68) has a viscosity of 67 at 40 degrees Celsius, so it's not that much thicker at that temperature than the others mentioned above, and still far less than the motor oil. As another measure of how they hold up to heat, the thickest AMSOIL hydraulic oil (ISO 68) has a viscosity of 11.7 at 100 degrees Celsius (212 degrees Fahrenheit) versus 18.1 for the 20W50 motor oil. Note -- don't rely on Viscosity Index (VI) numbers alone, because they measure the changes in viscosity between cold and hot, on an inverse scale -- the higher the VI, the less the change. I also told the rep I was looking for high viscosity between 100 and 150 degrees Fahrenheit, and he concurred that motor oil would likely perform better in those temp ranges, being specifically formulated to maintain a high viscosity at high temps. As I said earlier, he also said that foaming shouldn't be a problem either...