Why Do Cars Have Different Highway And City MPG?

Anyone who's regularly visited a gas station in recent years can tell you that fuel prices have been all over the place. They'd also tell you prices continue to err on the side of expensive, and that seems unlikely to change anytime in the near future. Given the facts, a vehicle's fuel economy numbers have, arguably, become one of the most important factors people consider when purchasing a new car, truck, or SUV.

Some consumers are, of course, trying to off-set the financial burden of fuel by purchasing one of the more highly-rated hybrids on the market. Others are even ditching fossil fuels altogether by getting behind the wheel of an all-electric vehicle from one of the major auto manufacturers. But gas continues to be the go-to juice for many vehicles currently on the road, and average miles per gallon (mpg) remains a prime factor in their overall market value. 

However, figuring out how many mpg a vehicle gets is not always as simple as you might hope, largely because there are two separate numbers to account for. If you've researched a new vehicle online or at a showroom of late, you've no doubt seen both numbers listed on its spec sheet, one being city mpg and the other being highway mpg. If you've ever wondered what exactly sets those figures apart, it's largely a matter of the driving conditions a vehicle endures in each setting. Here's a closer look at why city and highway mpg are different. 

Before we explore what causes differences in city and highway mpg, we should explain how mpg is measured. The name is pretty self explanatory, as mpg measures how many miles a vehicle travels in comparison to how much fuel it consumes along the way — i.g. a rating of 35 mpg means your vehicle can travel 35 miles on one gallon of gasoline. Those numbers fluctuate based on the make and model of your vehicle, as well as what grade of fuel you use, and your driving habits. They can also vary based on where you drive.

The difference between city mpg and highway mpg can vary as much as 5 mpg or more. The reason for the disparity is pretty simple, in that city driving puts more strain on an engine, thus increasing the amount of fuel you use in urban landscapes. That is primarily because city travel involves a lot more stop-and-go driving, with the constant off-and-on use of the gas pedal draining fuel quicker than the steady charge you'd see on the highway. Likewise, idling dramatically decreases fuel economy because it involves the burning of fuel without the vehicle moving.

If you're looking to purchase a new or used car from a dealership, both highway and city mpg will likely be showcased on the vehicle's spec sheet. So too will what is arguably a more important number in the vehicle's combined mpg, as it averages both the highway and city figures to give a more rounded picture of the actual mpg rating.

Apart from changing the sort of car you drive, there are other measures you can take to maintain or potentially even increase your vehicle's fuel economy. That list includes keeping up with the vehicle's regular routine maintenance, using a better grade of fuel, and, of course, altering the way you drive, with the rule of thumb being that aggressive driving is the enemy of fuel economy.

But if you'd rather just upgrade your mode of transportation, it's worth noting that there are fuel efficient models being made by virtually every major auto manufacturer these days. So if you are hot to get behind the wheel of a car, truck, or SUV with a solid combined mpg, there's no reason you shouldn't be able to do so.

In our own ranking of 2025's most fuel efficient cars, we found that there was one particular build that stood apart from the pack in the fuel economy game, with the 2025 Toyota Prius Hybrid's combined 57 mpg (57 City/56 Hwy) for the LE trim besting the closest competition by several mpg. The runner up on that list is the Hyundai Elantra Hybrid Blue, which clocked in at 54 MPG Combined (51 City/58 Hwy), and the Kia Niro FE rounds out the top three at a combined 53 mpg (54 City/53 Hwy). Perhaps the best news of all is that you can score any one of those vehicles for under $30,000 these days.