Hey so I've my 09 sport has the 5.7 and I used to get awesome fuel efficiency, upwards of 13.9L/100 hwy (20 MPG for you Americans) and life was good. Lately I've been getting upwards of 20 L/100 on average (around 14MPG) and I can't figure out why... I had the dealer do a full tune up about 25,000 km (15,000 M) ago with plugs, injection and throttle body service. I'm also running synthetic oil and I've checked the air filter and all of the obvious causes (tire pressure, etc.).
I'm currently running an S&B intake with an Air Raid throttle body spacer. I haven't gotten around to the programmer or cat back exhaust yet but its on the list. Could my mods be screwing with air/fuel to the point it pooched my cat??
I did buy larger tires - Toyo Open Country AT2's (295/60R20)... yea I know they'll effect economy but that much? My buddy has an 11' ram sport with 37x13.5's and hes killing my economy... I don't get it. It's hasn't flipped any codes. Anyone have any ideas? EGR?