if you really want to get better results get an ultra gauge. Seriously the best $65 i have ever spent for fuel economy, it will pay for itself down the road. Its a small lcd screen that plugs into your obd-2 port and can display 6 gauges at once based on ecu data feeds to the obd-2 port. It can track all number of things but my current setup is instant MPG, RPM, engine temperature, Short trip MPG, Trip MPG, throttle position #1.
gauge breakdown:
Instant MPG: What your car is getting at this very second
RPM: engine revolutions per minute, tachometer(redundant, but i like to have my rpms here)
engine temperature: self explanatory but very nice since we don't have a real temperature gauge for our cars
short trip MPG: MPG average from you start the car until you turn it off, resets every time. For my work commute my average is about 46mpg over 30 miles, with my lowest being 37mpg(i was late and driving 75mph) and my highest trip being 53.7mpg(i was trying very hard and safe-drafting a semi truck for about 15 miles).
Trip MPG:Average MPG from when you set it, to when you erase it, will not reset on its own. I've had mine going for 34k miles(life of the car) and am currently at 40.5, it's steadily going up now that i commute. This number includes everything, city driving, highway driving, autocrossing, late to work fast inefficient driving, sitting at the drive thru, everything.
throttle position #1: I honestly don't know what the difference between position 1 and 2 are, but i've always used throttle pos #1 to track how much gas i am giving the car exactly. foot off the pedal reads 32% if i remember correctly, with flooring it reading at around 76%, also if i remember correctly, generally only floor it when autocrossing. The perfect sweet spot for maintaining speed on the highway/most efficient seems to be 35.7% from my testing. Originally 35.3 seemed to show better numbers but you would very slowly lose your highway speed, or any road irregularities/even the slightest incline would drop you too far down and you would have to correct with harder acceleration. 35.7% can usually handle minor road irregularities and very slight inclines without correction, and constant throttle is always the most efficient method.