Re: 2005 Escape Hybrid Mileage Drop
If the battery was going I'm sure you'd notice it in terms of when the engine kicks on and off, and more regularly even with the A/C, lights, fan and radio all off. You can get Shell 91 octane, it has NO ethanol. Their 89 has a small percentage. At least in Canada.
Other things to check:
Did you replace tires recently with a more aggressive tread? Check tire pressure manually.
Did you slowly gain weight over the last few years where it would be noticeable?
Have you been doing more idling, or driving the vehicle differently?
Have you been allowing other to drive the vehicle? They might speed...
Air filter getting dirty?
Change in job or lifestyle where you travel higher speed roads or different altitude?
New spark plugs in the last 20K?
You can also try a different fuel supplier, even if its a touch out of your way it'd be worthwhile to try it out, or the next grade up, perhaps.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!