MPG numbers - actual vs calculated

Goseki said:

Am I doing something wrong? 2018 Civic Touring, 3000 miles, I drive a lot of city, AC/heater is usually set on low, gas mileage is usually around 25mpg. RPM usually at 1.5 to 2.5

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No. You are not doing anything wrong.
That is what the car gets in urban driving (despite what many claim).

Goseki said:

Am I doing something wrong? 2018 Civic Touring, 3000 miles, I drive a lot of city, AC/heater is usually set on low, gas mileage is usually around 25mpg. RPM usually at 1.5 to 2.5

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I don't think you are doing anything wrong. I also average 28mpg.

Only once, on the highway, I set the ACC behind a slow 58mph truck and followed that for 95 miles. That one time I got 52mpg. That's impossible in the city.

39 avg according to fuelly. And this is at 65 mph, 85% highway. My dash reports 3 mpg higher at all times.

38-41 MPG actual, dash is typically 5% higher.

My daily commute is about 25 miles of northern Virginia back roads and sitting in traffic on 495 - this generally gets me about 30mpg

On weekends I travel up and down 95 with about 80% highway/20% city - this generally gets me about 35mpg.

My dash is almost always within 0.2mph of my actual mpg.

I just took a 275-mile trip where I got to stay around 75-80 MPH during a lot of it. I had to do a lot of downshifts and upshifts during it, but that is to be expected. The A/C was running during the majority of the trip at about 67 degrees set to Auto, or sometimes circulated. I run 91 octane from Shell (I can't realistically get 93 and don't think I'll see any gains running stock parts and tune anyway).

However, there was a lot of weight added to the car. There were four of us, and the entire trunk was packed. I can't begin to guess the weight of all of the luggage/items, so I'll pretend like it's just a fifth person. Let's say we added about 25% more overall weight to the vehicle.

That being said, I averaged 36 MPG. I'd like to see what I could do on that same trip someday with just me, myself, and I.

Around town, I average 34 mpg calculated; about 2 less than the computer. On my Christmas road trip (340 miles, interstate with a stop every few hours), the dash computer read 36.9 mpg, but my actual calculated was 38.6 - 2018 HB ST with 2800 miles on it running 93 octane (Shell premium). Needless to say I’m happy!

I've got a 17 Si and I only put regular 87 octane in it.
City driving: Calculated 31 Actual 29
2400 mile trip across the country avg 70-80 mph: Calculated 36 Actual 34