I just purchased a 2003 TL type S with almost 130K miles. I am getting 24 mph on the open road which is much lower than expected. I replaced the plugs and installed a K and N air filter. Not much change. Reasearch indicated I should expect 27 to 30 mph highway. Is this correct? I did use the NGK plugs recommended on a previous thread. If the intake or EGR valve was soiled why wouldn't you get a check engine lamp? The car does seem to run smoothly. I am very surprised at the sluggish acceleration (compared to my 2002 Jeep Grand Cherokee). On a different subject I am having difficulty getting a straight answer on what service options I have for my transmission. The dealership said there is no replaceable filter and I have to use the ATF DW1 fluid. In the next breath they said i should let them flush the system with some Valvoline fluid. Any thoughts on any of these subjects would be greatly appreciated.

 

Welcome to the forum.

As for your question. Location helps. Are you in a winter climate? What is open road? All hwy, some hwy? what length of trip are you figuring out your MPG. At what speed are you driving?
You may not be getting a CEL because it may not be plugged enough to trigger it. You may also need the fuel injectors cleaned. If your acceleration is sluggish compared to a JGC something is wrong.

There isnt a pan to remove on these cars, so the typical trans fluid change there is no filter and pan to remove and replace. There is a serviceable filter on top of the trans that can be replaced. If you change your own oil, change your own trans fluid. Its just as easy. When changing only 3 quarts of nearly 8 come out. Drain 3 and drive it for a few weeks then repeat. Do this 3 or so times. Id stick with the New honda fluid or Redlines atf that works in our cars. Dont flush the trans. Honda does not want these trans flushed. And dont use the valvoline.

 

Another thing that will help as others will tell you Sea Foam... What gas are you using btw? Octane and brand.

 

I average a very consistent 21.6 mpg. I cruise at 85 on the highway, and in the city I tend to accelerate a little quicker than needed.

 

ah, forgot to mention the car! 03 TL-S with 179,xxx on the clock