Resurrection.....
So today I did some testing using a recently installed Mocal high-temp (202*F) thermostat. This type of thermostat, as David mentions above, is a bypass type. It never totally closes off either passage. Instead, the increased resistance to flow created by the cooler, and the longer flow runs, makes the oil bypass through the thermostat. As the oil temperature gets near the thermostatic temperature, the bypass starts to close and force more oil to the cooler. Even with the thermostat fully deployed there is still some internal bypass.
Two tests were performed. First, the car was run for about 1/2-hour in various street and highway conditions with the cooler plugged and oil temperatures noted. This allowed no oil to get to the cooler, hence, zero external cooling. The next test was to re-connect the oil cooler and do the same driving loop. Ambient temperatures were within 2* for both tests.
The total increase in the hose length of cooler connected vs. dis-connected is approximately 24". -10 lines are used. The cooler is located after the first pass of the dual-pass radiator. On most days the car can easily run with a block-off plate covering the entire first pass and still run cool without the fan coming on excessively, i.e., the car has excessive cooling capacity. The temperature sensor is placed at the bottom of the the oil pan sump. New Torco 5W-30 oil is used.
Results? No significant difference in overall oil temperatures. But here's the kicker. The oil temperatures never went over 155* in either test even when some "spirited" canyon driving was done. The ambient temperature is only 55*F so it is pretty cold. The coolant thermostat in the car is 160*F.
Warmer/summer ambient temperatures will hopefully bring up the temperatures.
So, the Mocal bypass thermostat is doing what it is supposed to do. It would be very nice if an aftermarket LS-series pan was available that utilized the stock LS small-body filter mount and location, an internal thermostat bypass, and the current ATS trap-door design. I'd gladly have paid additional money to clean up the installation and reduce the number of external hoses.
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