I had bought a 2002 Chevy Venture LS, 2wd, 3.4l 2 years ago with 74,000. It started out getting about 22 mpg but has consistently dropped over the past 2 years and is now currently at 18.5 mpg. Drive the same roads same driving habits. It has 102,000 miles on it now. I changed plugs, wires, fuel filter and air filter 2000 miles ago thinking it would make the mpg go up but it is still dropping. How should I go about troubleshooting the problem. There is no noticeable difference in how the engine runs and no cel. Thanks for the help.

 

any tire wear/pressure problems?...cleaning the injectors could help

 

There are many things that can affect mpg. They usually throw a code. O2 sensors, MAF sensors, vacuum leaks, etc. Keep checking everything and don't overlook the obvious.