RV-9. Sensenich FP. Lyc O-320-D1A. I have a Vans Oil Temp Gauge. I have the oil cooler about 75% blocked by 1/2 cover over the inlet and the outlet is completely closed except for 1/4 inch hole. At P.A. 3K feet, OAT=40F, 2500 RPM, IAS=185. After about 3 minutes the Oil temp rises to 140 and then will suddenly drop to 110 and start climbiing again. But it never goes above 130??!! Oil pressure is 78. CHT is 280. .. Bad gauge? Bad thermister? Thx. Rolly