Toyota Repair: 2001 Toyota Avalon low MPG, avalon xls, catalytic convertor


Question
Hi, i am seeking for answers to a few questions regarding my avalon.

I purchased this 2001 Avalon XLS a month ago, with 81K already on it. For some reason, i am only getting 10 to 11 MPG for driving here in Upstate NY. I asked several friends who has the similar model (2000 and 1998), but they all have a MPG in the mid twenties for city and around 30 for high way.

i took it to the dealer to have it inspected but they told me there's no problem with it. There are no warning lights at all on the dash board either.

Could it be possible that the problem may be caused by the catalytic convertor, air cleaner, engine sludge, or any thing else? The dealer told me the warning light would have come out if those were the case. How can i check to see if they are all working? (can you tell me where the air cleaner(filter for the intake) is exactly, please?)

there are also problems like high idle rpm when starts in cold (2000 for a couple seconds, then at 1500 for couple minutes, then back to 850)
and fuel/coolant smell coming out of the car even after half an hour of driving. (not noticeable inside the cabin).

Could you kindly help me out please? Thank you so much!

Answer
By any chance is the dealer you took it to the same one that sold the car to you?
If so, I would take it to another one and have them check it or get a second diagnosis anyway, it sounds like there is a major problem, if you can smell coolant/fuel, the air filter is located in the black box next to the battery, undo the clips to get it out.