lhecorolla 
2010 Toyota Corolla Sedan LE 4dr Sedan (1.8L 4cyl 4A)
low mileage 
 I have it since 2010. I'm driving 80% - 90% on highway, around 70mph, usually full load, 4 persons. Now, it shows only 30mpg when I add gas. I've been watching in different weather, hot/warm/cool, it is around there. The meter in the car stills shows 36mpg which I don't understand. Can someone tell me why? how to improve it? 