2007 PRIUS , 2000 Chevy PRIZM ( Corolla ) owner> MOBIL 1 at 74 ,000 mis.

started doing own oil change again and decided to go from regular oil in the 2000 PRIZM ( lab rat for the PRIUS ) to MOBIL 1 at 74,000 mis.. Since the change to synthetic have noticed that temp gage needle dropped from 1/2 way (pre syn-oil) to about 1/4" lower with the MOBIL 1 ( over 1,000 miles since the change ) ( :blink: ) . Also , the 2 of us went out of town shopping since the switch to the MOBIL 1 and the 5 speed manual PRIZM got 40.2 mpg ( around 1/3 city , 2/3 highway(69 mph avg.)). Coincidence ? Last , was told to change oil sooner since the switch because of the cleaning power of synthetic oil . If so , should I do the oil change at 2,000 or 3000 mis. as a flush and then go with a full synthetic or possibly a blend at 4,000 mile intervals ? Thanks