What mileage can I expect with my 04 TL? Currently on highway getting 23 mpg, this seems low to me. I had a 01 TL that got 30 +.

 

Hello.
Every Single one of us will have a different driving style..furthermore, every single one of us will have a different commute, different traffic patters, different elevations, etc.
one cannot tell you the expected mileage...as it will be different for so many different people.

you can, however, check the display on your dash and look at the average speed you're traveling at..
average speed will dictate average milage.

my current average speed is 23mph and I am getting about 21-23mpg.

 

I agree with the thought 23 mpg sounds rather low when doing highway driving (unless you have your cruise control set in excess of 100 mph). In summer weather my 2006 6MT model typically averages about 32 mpg on the highway and on cold winter days more like 29-30.

 

Fix the other issues in your car before determining the baseline MPG. They are more than likely related.