I have a white 2005 Toyota Sienna LE automatic trans 6cyl. minivan with over 200K on it. Runs great except in the past year my gas mileage as of the readout in the little screen on the ceiling in the center above my head went from 23.3mpg down to 17.7mpg in about 6 mos time. The codes I'm told by a local garage say it's running too lean. I also asked about the O2 Sensors. The mechanics say that they would have to spend a certain amount of time to determine exactly what needed to be done but because of the high mileage I'm supposed to just live with it. But when I first got it 3 yrs ago the mpg was 23.3 for quite a while and the mileage was still over 200k. We don't drive it all that much, mostly around town. I was told that it had a lot of highway mileage but was well taken care of. Earlier this year I replaced the Mass Air Flow Sensor which I cannot tell if it even did anything to the Van. It actually runs great, has good acceleration and idling. Transmission seems ok. But it does use a lot of gas. There have even been times when to me it smelled rich coming out of the tailpipe. I'm familiar with cars from the 50's to the 70's but not this kind.