Art: When I redid my car recently, replacement of all S/W was part of the project. I chose the 2 5/8" mechanical gauges (
Oil/Water) I tested them both by putting the send unit bulbs into a container of hot water from the stove. Using my wifes kitchen thermometer (thanks Honey) to monitor the water temp I determined that each of the gauges ireads almost 20 degrees low. While driving with 180 degree water thermostat veified to be functioning properly the gauge reads indicted 160 degrees.
Oil gauge reads 160 degrees while running down road at 2800-3000 cruise RPM.
Oil cooler has a clear 1/8 thick piece of plastic in front to prevent airflow. Running about 11 quart oil capacity with pan, cooler and lines. As far as the accuracy I was disappointed to find they were as far off as they were, I may adress this in the future but for now I just watch the gauge to be sure it is stable at an "indicated 160"!
http://www.stewartwarner.net/
Rick