Other factors will affect mileage much more than than the battery. It's more about battery management than gas mileage. The dash will give you a rough estimate, but with an OBDIIC&C gauge you will see exactly what's happening. The behavior you saw with the old battery was a lot of recalculations. Each car, battery, and driving style is different, but the new one will probably "normally" stay about 3 bars from the top.I drove about 1000 miles to Covina on a bypassed battery and got very decent MPG. The Honda was sluggish at low gear and low speed but did fine on the freeways. Then I drove back with a new battery and only used the clutch switch for the long, steep hills. The mileage was considerably lower, perhaps because I had the AC on (at 70F).
I understand that the reason to have a clutch switch is to avoid battery depletion. Can you judge battery depletion just by looking at the IMA bars? In the final months of my old battery (may it rest in peace) typically it would spend days around 10 bars, then build up to 18 or 19, and suddenly plunge all the way to rock-bottom 2. So how many minimum bars should you aim at for a healthy charge?
+1 to using a DPDT ON OFF (ON) switch for this, as recommended by IC user retepsnikrep in another thread long ago. My complicated steering wheel setup with two momentary S2000 cruise control buttons wired to a circuit board could actually be replaced and simplified by a simple DPDT ON OFF (ON) switch wired to the steering wheel mount, or perhaps the shifter. Rig the clutch switch to the maintaining side and the brake switch to the momentary side. Drive around with clutch switch on at all times, but if you need to regen you flip it to the momentary brake side. You might still have to do some of my stuff (Scenarios #3 and #3 A in post above) to get regen working, but it's going to be more ergonomic.Brake switch lets you get maximum regeneration without stepping on the brake and to keep autostop active longer while coasting. Brake and clutch switches can be wired into a single 3 position switch.
I'd be more concerned about killing the engine by frequently redlining it than killing your IMA.I just don't want to kill my IMA when I won't need it on the freeway for 6 hours.
Too much effort to reconnect my already programmed off-road Arduino mod to be able to redline my G1 in the lower gears!