Agreed, divide miles driven by how much gas you actually put in to fill. The only time tank capacity would be used is if you ran it bone dry and pushed it to the gas station. Lol.
There are LOTS of tricks with a stick that can be used.
My usual arsenal consists of:
-Shift low. Most cars I've driven respond favorably to shift points at roughly 1800-2000rpm. Lower than that seems to be a gamble as with some cars it puts too much load on the engine (which hurts economy). This may take some trial and error, or data logging, on your part to see what your car “likes”. Keep in mind, this only applies when you’re accelerating. Once at cruising speed put it in the highest gear possible.
-When in doubt, pick the higher gear. Cruising in 3rd gear in town is a sure fire way to kill your mileage (I’ve seen it done). 90% of the time you will be able to use 5th at any speed above 25-30mph. If you need to accelerate with a little gusto for some reason, drop it down a gear.
-COAST, COAST, COAST! Sticks are the kings of coasting, use it to your advantage. Push the clutch in and glide as much as possible. With a careful eye and a little luck, you can alternate light throttle and coasting and make it through consecutive traffic lights without stopping, sort of a "pulse and glide" in town. Now, you’ll inevitably have someone riding your bumper doing this but they are the same people that will gas it hard off the red light and then be forced to slam on the brakes at the next so just ignore them. Maintaining a steady pace without stopping will have you’re mpg’s climbing like crazy.
Now, some people (like your friend) will tell you to coast in gear. What they’re trying to do is get the car to go into fuel cut (most new cars will cut the fuel when coasting) but in my experience, doing this with a stick cuts you’re coasting distance a TON as the direct connection between the engine and drivetrain makes for a LOT of drag when off the throttle (engine braking). The tiny amount of fuel an engine uses to idle is more than made up for by the fact that you can coast SO much longer with the clutch in.
-The kinda goes with the previous point, Coast down hills (even small ones). Pushing in the clutch and coasting down hills can be done without losing speed and impeding traffic even on very small hills. Just remember: when you’re moving any decent speed with the clutch in and the engine idling, you’re getting 100mpg+. The more often you can do that the more it’ll bring your overall average up. There are a LOT of opportunities to coast in town, look for them and use them.
Overall though, it seems like you’re doing VERY well already. 335 miles on 8 gallons is 41.9mpg.
A little different than the Expedition, huh.