You can add more timing with the more % ethanol you have in the fuel, the more octane, also more octane. More octane or more alky, the slower the burn, so more timing helps that delay.
Not much, but a couple degrees. Also, 1 degree increase per 1000 foot altitude increase too.
Does the L05 have knock sensor(s)? Got to be protective of it, pinging is damaging, it rattles the engine dangerously internally. Avoid at all costs. If it takes a couple degrees to protect it, use them.
A cooler thermostat will also allow higher timing. I wouldn't hesitate using a 160 in the summer, as the engine is fully in closed loop by 100F in warmer weather, in cooler, 130F. So a 160 stat won't hurt that (this is a internet myth that I have busted years ago....)..
Run a 10W30 oil too, not a 5W30 or 0W30, when hot they are thicker than 10W30's. So they hurt mpg in warmer weather. Synthetics are rumored to seal rings better, so you might get a 1/2 to 1 degree more with them. MAYBE....
Oh, and in most every case, when tuned properly, 87 octane gets better mpg than 93 octane. It is easier to ignite, and if you can get away with it, widen the gap on the plugs as much as you can until mpg drops, then go back a bit. A more potent coil helps too.
We get 0.045 gap on our cars, maybe if we are lucky 0.055. The 4cyl, V6 and V8 cars with the individual coils (1 coil with 2 plugs on it) get 0.060, which being it is a waste spark, is really 0.120! So more coil power can help too. If you can get a hold of a higher turns ratio coil, that might help too, with a wider gap that is.
Also, if you are the nutty experiementing type, look into the plugs for the 8.1L V8's (2000-2006 8100 pickups/rv's) and see if they will work without hitting the piston. It puts the gap farther out in the cyl so you get a better cleaner burn away from the chamber wall.