Terrible 4 cylinder mpg

My truck: 2013 AC 2.7L 4x4 M/T (stock except bed cover, probably about 30-40 lbs. additional weight)

• I've filled my tank at the same gas station 98% of the time.
• I've always filled my tank as the gauge reached the last line before E(mpty).
• I've always used 91 octane gas (Shell).
• I've always topped off the tank by letting the pump stop itself automatically and not adding a few more drops after.

I think I've been quite consistent with how I filled my tank.

• Is there anything wrong with my method?
• Is there anything I could improve to get better accuracy?

 

Your method looks good to me. Much more thorough than most. My only comment, given the accuracy of the gas pumps and the odometer, is I would question the 3 decimal points in the mpg column. Simple error analysis from my engineering days. Nit picking.

 

If I used the trip meter on the dash, I'd probably get decimals for the mile reading, too. But I didn't want to go there because I'm sure I'll forget to reset the meter every time I fill the tank. And you're right, this really isn't 100% accurate. Hmmmm...

 

I run Mobil1 synthetic in my 11' RC 4WD manual Tacoma. Highway speeds for me is 75 mph. I get at best 20-21 mpg highway and average about 18 mpg city. When I get time off next month I want to change out my drivetrain to all synthetic.