[E4ODnut]

How lean you can run your engine will depend on the engine. Also, one thing to consider is that your wide band may not be 100% accurate. It's not uncommon to have a significant difference between makes, 0.5 or more. That's of no major consequence because you'll likely just be tuning with one and it's the relative readings that are important to document what your engine likes.

You will definitely get better mileage with leaner mix. I have fuel burn read outs with my systems and they confirm it. If you don't already have one the MPG instrument offered on this site would likely be a good investment so you can track your changes.

I've found with all of my engines, I can get between 17 and 18:1 indicated before I get any sign of a lean stumble. I've run as much as 19:1 but that was on a very light load, and my engines are almost never at that power setting.

I've also found that is beneficial to add quite a bit of timing with the lean mixtures as they burn a lot slower than a richer mixture will.

It takes a lot of experimenting, and data logs are your best friend