Mike Easley wrote; I also ran some viscosity tests on … None of them performed very well. … All of the oils lost about half of their viscosity (measured in time) in only 30 degrees F… Mike, I serviced my 360 strut with Mobil 1 75W-90 gear oil several months ago. The dampening is very
high, which I like. I find it easier to taxi in a straight line and easier to back it into the hanger without a tow bar. I had no problems this winter before or after flights in temps down to 20F. It has a pour point of -51F. | Mobil 1 Synthetic Gear Lubricant LS |
| | SAE Grade | 75W-90 | | Viscosity, ASTM D 445 | | | cSt @ 40ºC | 106 | | cst @ 100ºC | 15.2 | | Viscosity Index, ASTM D 2270 | 150 | | Pour Point, ºC, ASTM D 97 | -46 | | Flash Point, ºC, ASTM D 92 | 175 | | Density@15C kg/l, ASTM D 4052 | 0.859 | Mobil 1 15-50 has a lower viscosity. | Mobil 1 15W-50 |
| | SAE Grade | 15W-50 | | Viscosity, ASTM D 445 | | | cSt @ 40º C | 131.2 | | cSt @ 100º C | 18.1 | | Viscosity Index, ASTM D 2270 |
154 | | Sulfated Ash, wt%, ASTM D 874 | 1.21 | | HTHS Viscosity, mPa•s @ 150ºC ASTM D 4683 | 4.50 | | Pour Point, ºC, ASTM D 97 | -39 | | Flash Point, ºC, ASTM D 92 | 235 | | Density @15º C kg/l, ASTM D 4052 | 0.87 | My
theory is that builders could ratio these two fluids to provide the dampening level they desire. The synthetics have viscosity index improvers claimed to provide a flatter vis/temp curve. Mike, Would you mind testing these two materials and reporting back? I notice that the flash point of the 75-90, 347F, is less than that of the 15-50. Does anybody know what the critical temperature would be with air at the pressures we run?
I recommend nitrogen, although I used air due to availability.
BILL HANNAHAN
WFHANNAHAN@YAHOO.COM
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