A paid-off older vehicle can be cheap to own, but poor fuel economy changes the equation when you drive a lot. Consider an older truck, SUV, or other gas guzzler worth about $5,000 that averages only 13 MPG.

If you drive 20,000 miles per year and gasoline averages $6 per gallon, could trading that inefficient vehicle for a $25,000 used car actually save money?

More importantly, what if you do not want to replace your gas guzzler with a boring economy car? What if you want something that is actually fun to drive?

The other costs of switching to consider include your use case. If, like me, you don’t tow or do any serious offroading, it might be worthwhile to make the switch. So, is it possible to justify switching to a more fuel efficient vehicle despite the costs of changing?

The Starting Point: A 13 MPG Gas Guzzler

Our example assumes the following:

• Older truck, SUV, or other inefficient vehicle
• 13 MPG average fuel economy
• $5,000 trade-in value
• $25,000 replacement vehicle
• 20,000 miles driven per year
• Six years of ownership
• $6 per gallon gasoline

At 20,000 miles per year, the vehicle will travel 120,000 miles over six years.

How Much Does the Replacement Car Really Need to Save?

A $25,000 replacement does not create a full $25,000 additional cost because the current vehicle can be traded or sold for approximately $5,000.

For the replacement vehicle to recover that entire $20,000 through fuel savings alone, its six-year fuel bill must be at least $20,000 lower than the gas guzzler’s.

The 13 MPG vehicle costs about $55,385 to fuel, so the replacement vehicle can consume approximately:

At $6 per gallon, that works out to a break-even fuel economy of approximately 20.35 MPG.

In other words, you do not need a 50 MPG hybrid for the switch to make financial sense. You simply need a vehicle that gets substantially better mileage than the old gas guzzler.

What Happens With a Sporty Car?

This is where the numbers become interesting. Plenty of enjoyable driver’s cars return fuel economy in the mid-20s or better.

The table assumes every replacement vehicle costs $25,000, receives a $5,000 trade-in credit, travels 120,000 miles, and uses $6-per-gallon gasoline.

The important takeaway is that even a relatively thirsty sports car can potentially work.

If, like me, you’d only make the change if the numbers make sense, and you can’t stand the thought of being in a boring econobox, below are a few options to consider.

Ford Mustang EcoBoost: Sports-Car Performance Without V8 Fuel Economy

The Ford Mustang EcoBoost deserves a place on this list because it provides something most of the other cars cannot: the look, driving position, rear-wheel-drive layout, and general experience of a traditional American sports coupe while still returning reasonable fuel economy.

Yes, it is a little unfortunate to buy a Mustang without the V8. The sound and character of the 5.0-liter GT are a huge part of the Mustang’s appeal. But the EcoBoost is hardly slow. Its turbocharged 2.3-liter four-cylinder produces 310 horsepower and 350 lb-ft of torque, which gives it plenty of pep for daily driving, highway passing, and a winding back road. Ford offered it with either a six-speed manual or 10-speed automatic.

That torque figure is particularly impressive when you compare the EcoBoost with something as common as a Toyota Camry. A 2020 four-cylinder Camry produces 203 horsepower and 184 lb-ft of torque. Even the 301-horsepower Camry V6 produces only 267 lb-ft.

The comparison with the Camry TRD is especially interesting. The EcoBoost Mustang actually makes slightly more horsepower and considerably more torque, while both were rated at approximately 25 MPG combined in these configurations. The Mustang also sends its power to the rear wheels rather than the front.

Performance is legitimate, too. Car and Driver recorded a 5.1-second 0-to-60 MPH time from a manual EcoBoost Mustang, putting it firmly into sports-car territory. For comparison, the publication recorded 5.6 seconds from the 301-horsepower Camry TRD.

At 25 MPG, our 120,000-mile example would require approximately $28,800 in gasoline at $6 per gallon. The 13 MPG gas guzzler would consume about $55,385 over the same distance, so the Mustang would save approximately $26,585 in fuel.

After subtracting the $20,000 net cost of upgrading from a $5,000 vehicle to a $25,000 Mustang, the simplified calculation still leaves approximately $6,585 in savings.

That makes the EcoBoost Mustang an unusually appealing option for this exercise. You give up some efficiency compared with a Civic Si or Miata, but in return you get a 300-plus-horsepower, rear-wheel-drive coupe that looks and drives like a proper performance car. For someone escaping a 13 MPG gas guzzler, 25 MPG is still enough of an improvement to make the numbers work.

A 22 MPG GR86 or BRZ would use roughly $22,700 less gasoline than a 13 MPG gas guzzler over 120,000 miles. That is enough to approximately offset a $20,000 net vehicle upgrade under these assumptions.

Move into the upper-20 MPG range and the numbers become much more favorable.

Honda Civic Si: The Financial Sweet Spot

For someone who wants an enjoyable driver’s car without sacrificing fuel economy, the Civic Si is an especially interesting option.

It combines a manual transmission, limited-slip differential, relatively low weight, usable rear seats, and approximately 30 MPG combined fuel economy depending on model year.

At 30 MPG, 120,000 miles requires about 4,000 gallons of gasoline. At $6 per gallon, that is approximately $24,000 in fuel.

Compared with the 13 MPG vehicle’s projected $55,385 fuel bill, that represents more than $31,000 in fuel savings.

Even after subtracting the $20,000 net cost of replacing the old vehicle, the simplified calculation leaves the Civic Si owner approximately $11,400 ahead.

Mazda Miata: Maximum Fun Without Terrible MPG

If practicality is less important, the Mazda MX-5 Miata may be an even more compelling driver’s car.

The Miata is lightweight, rear-wheel drive, responsive, and designed around driver involvement rather than outright horsepower. Yet unlike many traditional sports cars, it can still return fuel economy close to 30 MPG.

At approximately 29 MPG, fuel for 120,000 miles would cost roughly $24,828.

That is more than $30,000 less than the projected fuel cost of the inefficient 13 MPG vehicle.

There are obvious compromises. You get two seats and limited cargo space. But purely from the perspective of turning fuel expenses into driving enjoyment, the Miata makes a surprising amount of sense.

Volkswagen GTI: The Practical Driver’s Car

The Golf GTI is one of the better compromises for someone who wants one vehicle to do almost everything.

It offers a turbocharged engine, strong acceleration, responsive handling, a usable rear seat, and hatchback cargo space. Depending on year and configuration, fuel economy can land in the upper-20 MPG range.

At 27 MPG, our six-year fuel bill falls to about $26,667.

That produces nearly $28,700 in fuel savings compared with the 13 MPG gas guzzler and approximately $8,700 in savings after accounting for the $20,000 net vehicle purchase.

Elantra N: Trading Some Economy for More Performance

The Hyundai Elantra N moves farther toward the performance end of the spectrum.

It is significantly more powerful and aggressive than a typical economy-oriented sport compact, but fuel economy is correspondingly lower.

Even at 25 MPG, however, the numbers still work surprisingly well in this scenario.

Fuel for 120,000 miles would cost approximately $28,800, saving about $26,585 compared with the 13 MPG vehicle.

After the $20,000 net cost of switching vehicles, that still leaves approximately $6,585 in theoretical savings.

GR86 and BRZ: Near the Lower Limit

The Toyota GR86 and Subaru BRZ are arguably closer to traditional sports cars than the Civic Si, GTI, or Elantra N.

They are rear-wheel drive, low to the ground, relatively lightweight, and focused heavily on steering response and chassis balance.

The tradeoff is fuel economy.

At around 22 MPG in this example, fuel over six years would cost approximately $32,727.

That is still about $22,657 less than fueling a 13 MPG vehicle. After accounting for the $20,000 net vehicle purchase, the calculation remains about $2,657 positive.

This is close enough to break-even that insurance, maintenance, registration, financing, depreciation, or premium-fuel requirements could easily change the result.

The Real Target Is About 25 to 30 MPG

The mathematical break-even point is only about 20.4 MPG, but that does not mean a 21 MPG vehicle should be the goal.

A better target is roughly 25 to 30 MPG combined.

That range creates enough of a fuel-cost advantage to provide a cushion for other ownership expenses while still leaving room for genuinely entertaining vehicles.

• 30 MPG: approximately $11,385 ahead after the net purchase cost
• 27 MPG: approximately $8,718 ahead
• 25 MPG: approximately $6,585 ahead
• 22 MPG: approximately $2,657 ahead

Fuel Economy Is Not the Entire Cost of Ownership

There is an important limitation to this calculation: it isolates fuel savings and vehicle purchase price.

A complete comparison should also consider:

• Sales tax
• Registration
• Insurance
• Financing interest
• Maintenance
• Repairs
• Tires
• Depreciation
• Resale value after six years
• Premium versus regular gasoline

The older gas guzzler has one major financial advantage: much of its depreciation may have already occurred. A $5,000 vehicle cannot lose $20,000 in value.

A $25,000 used car, by contrast, might still lose a substantial amount of value over another 120,000 miles.

On the other hand, an older truck, SUV, or high-mileage vehicle driven another 120,000 miles could require considerably more repair and maintenance spending. Larger vehicles may also cost more for tires, brakes, and other wear items.

Those costs need to be evaluated separately for the specific vehicles being compared.

Does Trading the Gas Guzzler Make Sense?

At low annual mileage or cheap gasoline prices, replacing a functional paid-off vehicle solely to save fuel is difficult to justify.

But this scenario is different.

Driving 20,000 miles per year at $6 per gallon makes 13 MPG extremely expensive. Over six years, a gas guzzler could consume more than $55,000 in gasoline alone.

That creates enough potential savings to subsidize a substantial portion of another vehicle.

The break-even point is only about 20.4 MPG, while many genuinely enjoyable cars achieve 25 to 30 MPG.

That means the decision does not necessarily have to be between keeping an inefficient vehicle and buying a boring economy car.

You could potentially move into a Civic Si, Miata, GTI, Elantra N, GR86, BRZ, or another efficient driver’s car and still spend less overall under the assumptions used here.

The Bottom Line

If an older truck, SUV, or other gas guzzler averages 13 MPG and is worth $5,000, replacing it with a $25,000 vehicle requires an additional $20,000 investment.

Over six years, 20,000 miles per year, and $6-per-gallon gasoline, the inefficient vehicle would consume approximately $55,385 in fuel.

A replacement vehicle needs to average only about 20.4 MPG for fuel savings to offset that $20,000 difference.

But the more compelling range is 25 to 30 MPG. At those figures, the potential six-year advantage rises to roughly $6,600 to $11,400 before considering depreciation, insurance, maintenance, taxes, and financing.

For someone who drives a lot and wants a sporty vehicle, that opens up an unusual opportunity: spend less money on gasoline while upgrading to something considerably more enjoyable to drive.