What could cause my gas mileage to drop even though I drive the same?

[AndrewKL]

I’m trying to figure out if my car’s fuel economy is actually getting worse or if I’m just imagining it. My last few fill-ups have given me noticeably fewer miles per gallon than I was getting this time last year, even though my driving mix of highway and city commuting hasn’t really changed.

[NicholasTM]

I started logging every fill and the miles since the last tank. After a cold snap last month my numbers dropped, but when I checked tire pressure I found two tires down around 5 psi. I inflated them to spec and did a long highway run; MPG ticked up a bit. If you’re seeing a drift, a quick check of tires, air filter, and oil level can help you separate the noise from the trend.

[Jonathan_M]

I used to think my MPG was worse, but I realized I was mixing up pumps and fill levels. If you don’t fill to the same line every time and reset the trip, the math will lie to you. Try filling to the same point and calculating miles divided by gallons, not the dashboard readout.

[Harper.H]

Weather, traffic, and road surface change things. I noticed that in winter fuel blends and cold starts the MPG drop happens even with similar driving. I remember a few tanks where I had a lot of short trips and more idling; it felt worse than it actually was once I started averaging properly.

[MilaVP]

Could the real problem be that your short trips and idling are actually the driver, not the car? Do you have a lot of short hops lately?