2006 hummer h3, 5 cyl. About 125k miles.
Used to get at least 15 mpg, now it's more like 10 mpg.
I changed the spark plugs, air filter, ignition coil.
Ran some injector cleaner.
Still no luck.
No engine light on/no code. My scanner is an actron cp9580 but beside reading and after repair removing code that's all I know to do with it.
The manufacturer's web site says it records live data - including things like a too rich fuel mixture.
Check out their how-to videos - bottom of page, under the price
https://actron.com/content/obd-ii-auto-scanner-plus
To be honest I have no clue how to use the scanner beside reading and erasing codes. I'm going to post pics of what the scanner shows.
Start with checking the fuel trim data.
Couldn't figure out how to add pics...here is a slideshow of what the scanner shows
I put 10 seconds between each slide so it can be read..