# What causes an engine to run lean **URL:** \ **Category:** PittSpeed Automotive\ **Created:** [April 20, 2007, 10:53pm UTC](https://forums.speedlife.net/t/what-causes-an-engine-to-run-lean/189422 "2007-04-20T22:53:35Z")\ **Posts on this page:** 1\ **Showing post:** 16
**Author:** ![xlogic](https://avatars.discourse-cdn.com/v4/letter/x/59ef9b/32.png) [@xlogic](https://forums.speedlife.net/u/xlogic)\ **Post date:** [April 22, 2007, 9:34pm UTC](https://forums.speedlife.net/t/what-causes-an-engine-to-run-lean/189422/16 "2007-04-22T21:34:51Z")
> [@How would you go about diagnosing this problem...](https://forums.speedlife.net/t/how-would-you-go-about-diagnosing-this-problem/29575/30): > > Yeah, that’s 15mpg if you’re filling it with 10 gallons or so. I’d be surprised if you were running lean and getting 15mpg unless you had a hole in the gas tank or something. no hole…hasn’t been any residue on the sidewalk since my tranny fluid leak which has since been fixed. but i will def start checking where you said and get you guys a pic as per danhr Edit: oh i’ll pull one of the first 3…threads on #4 are starting to scare me a bit since the oil was found in the 4th plug…i don’t have a donar head for my car and don’t want to ruin the head and have to get it rethreaded --- _[View the full topic](https://forums.speedlife.net/t/what-causes-an-engine-to-run-lean/189422)._