Check engine light isn’t on and I had the codes read. Gave me back 0 codes so I imagine it would be something else? Car idles normally I would say. Obviously it has an exhaust system so it vibrates more than a normal car. Thank you for your input.I'd get the codes read. None of what you wrote would cause poor MPG. I imagine your CEL is always on due to exhaust system so you may not notice the real code. Do that first. How does it idle? My first for real bad MPG is the O2 sensor as it will send way to much fuel. You will have an 02 code for not having a cat, but ignore that one as it doesn't meter fuel.