Why is my real-world mpg lower than the official rating?

[Nicholas_S]

I’ve been tracking my fuel consumption for the past six months and I’m confused why my real-world mileage is consistently about 15% lower than what the official combined figure advertised for my car says. My driving is mostly a mix of suburban roads and some highway, and I keep up with maintenance. It just feels like that number is impossible to reach without some very specific conditions.

[Logan_A]

Yep, that gap feels real. The official combined mpg comes from EPA tests under pretty controlled conditions, not from our daily detours and traffic.

[Benjamin.G]

For me it was tire pressure and carrying stuff—even small extra weight drags you down, and I noticed my numbers jumped a bit when I fixed that.

[Mila.G]

Cold weather, using the heater, and a lot of short trips can just eat into mileage more than you’d think.

[VictoriaPM]

Do you check the average MPG readout against the fill-up math, or could the math be off?