I just purchased a 2007 RDX a couple weeks ago. I have used a full tank of gas on it already and got my second tank in it. First off- is it normal to get better gas mileage out of a 1/4 tank with in town driving, then freeway driving? I managed to get 160km city driving on a 1/4 tank of gas, but once I got on the freeway, that went down to 100km on a 1/4 tank. It used 1/2 tank for 200km. Is this normal for the RDX?

Im wondering if adding a Magnaflow performance muffler will help it flow a little better, add a little more sound, and maybe make mileage a little better on the freeway? Im not sure what size of piping Acura uses from the cat back to the tips, but i see Magnaflow has some 2 1/4" muffler options which might work on the RDX. What do you guys think?

 

I don't know about the magnaflow but my 07 gets about 400km to the tank combined.

 

The gauges in these things aren't equally distributed across the tank. You might get 90 miles out of the first 1/4 of the tank. Then 75 out of the next quarter, then 60, then 50. The top of the tank is the widest and then when you get down to the bottom, you are dealing with the hump. So, if you drove the city miles first and then the highway, your results are to be expected. They could have done a much better job calibrating the gauge.

Picture borrowed from ebay

 

If you want more MPG you will have to get a custom downpipe fitted. Use the same flange on the stock cat bolted up to the turbo, put 3" pipe all the way to where the 2nd pipe connects to the cat back. To not have a check engine light you will need a extension on the 2nd o2 sensor fitted between the bung and the sensor.