Why is my real-world fuel economy 15% higher than the official figure?

[JonathanKJ]

I’ve been tracking my fuel consumption for a few months now and my numbers just don’t match the official combined cycle figure for my car. My driving is mostly suburban with some highway, so I expected to be close, but I’m consistently about 15% higher. I’m wondering if others see this big a gap in real-world use.

[Nathan_J]

Yeah I’ve seen that kind of gap too. My suburban plus highway mix usually lands about 10 to 15 percent worse than the label, especially when temps swing or the tires aren’t perfectly inflated. Real driving isn’t the lab, so the difference doesn’t surprise me much anymore.

[Grace_T]

I mostly compare gallons per tank, not the car’s guess, and I’ve found the trip computer can be off by a few percent. My most reliable approach is to fill to full each time and calculate by hand. It stays in that 10–15% range for me.

[Stephen_L]

One time I swapped to a better air filter and checked brakes for drag and nothing changed a lot. I still get a bigger number on the road than the official one. It’s kind of frustrating.

[DonaldSJ]

Did you ever compare the EPA figure to your own fill up math or just rely on the trip readout?