Is it normal for this engine to not reach the thermostat spec of 89 degrees? When i first noticed the engine at around 75 degrees i thought it was the thermostat, so i changed it, but it made no difference. So i connected a temp sensor on my multimeter and put it inside the top hose to see when water gets through the thermostat, there is a slight opening at 80 degrees, which sounds normal to me. Took a drive, at 30% load(normal driving,flat road, 90km/h) the engine is around 74-75 degrees, at 60%(uphill), the engine eventually reaches 80 degrees, the thermostat opens, and 10 sec later the temp drops to 70, and slowly climbs it's way back to 75. This is with an outside temp of 5 degrees and low heater fan speed, 0 degrees or lower, with high fan speed i can barely get 72 degrees, i never reach 80. Is this normal? Is there anything i can do so i can keep a decent cabin temp when the outside temp drops to -10 or lower?