OK, I have no idea how or why this happens, but it does and it was not just a one off thing. I can do this whenever. The Demon has a full digital guage with the oil light that is layyed out in an up-down direction with 8 possible bars that can be illuminated. Depending on temperature of motor/outside air temp. it is either at 4 or 5 bars. A real caold day with a cold start will register 4 all other conditions,it will read 5. This is the case until I turn my heater on HI at which time it will jump up 1 bar. If i shut the heater off it will go back down a bar. I have the Automatic temp control heater. Is there anyway those two items are electrically related?
The oil sending unit is a variable resistor, so the gauge works by measuring the voltage drop across it. Turning the blower on HI will drop your whole vehicle's electrical system slightly. That slight amount may be enough to give you an extra bar. That's about all I can think of...
OK that makes sense. I really gotta upgrade the alternator.....