This is the question everyone asks before they buy a bus, and honestly, the answer might scare you a little. But it’s better to know upfront than to find out at the pump.
Most converted school buses get between 6 and 12 miles per gallon, depending on the engine, bus size, weight of the build, and whether you’re on flat highway or climbing mountains. A typical full-size diesel skoolie gets 8-10 MPG on flat roads. Short buses do a bit better at 10-14 MPG. Gas engines tend to get worse mileage than diesels. After a full conversion adds 3,000-8,000 pounds of weight, expect to lose 1-2 MPG from whatever the bus got empty.
After all the additions, what happens to the gas mileage?
It goes down. That’s just the reality. Every pound you add to the bus costs you fuel.
A typical skoolie conversion adds 3,000-8,000 pounds depending on how heavy you build. Wood framing, tile floors, granite countertops, a full water tank — it all adds up fast. A bus that got 10 MPG empty might get 7-8 MPG fully built out and loaded with your stuff. (See our guide on Can You Get a School Bus with a Manual Transmission? for more on this.)
This is why a lot of experienced builders obsess over weight. Choosing lighter materials where possible — vinyl plank instead of tile, butcher block instead of granite, aluminum framing instead of steel — can save you thousands of dollars in fuel over the life of the build.
Is it really feasible to be driving that bus around when gas is over $3 a gallon?
It depends on how much you drive. And this is where a lot of people get bus life wrong — they assume you’re driving every day. Most full-timers move their bus once or twice a month.
If you’re getting 8 MPG and diesel is $4/gallon, a 200-mile move costs you about $100. Move twice a month and that’s $200 in fuel. Compare that to $1,500/month rent plus a car payment. The math still works.
Where it gets expensive is if you’re constantly road-tripping. Cross-country drives burn through fuel fast. A 2,000-mile trip at 8 MPG and $4/gallon costs $1,000. But most skoolie dwellers park somewhere for weeks at a time, not driving daily.
Isn’t it burning more fuel because it’s heavier than it should be?
Yes, absolutely. But “heavier than it should be” depends on what you’re comparing to. A school bus was designed to carry 40+ kids. That’s roughly 4,000-6,000 pounds of passengers. Your build probably weighs about the same — you just replaced kids with a kitchen, bedroom, and bathroom. (See our guide on Should You Buy a Gas or Diesel School Bus? for more on this.)
The bus’s engine, transmission, and suspension were built to handle that load. You’re within the design specs. It’s less efficient than running empty, but you’re not overloading anything. (See our guide on What’s the Difference Between Front Engine and Rear Engine Buses? for more on this.)
The fuel economy hit from added weight is real but predictable. Budget for 7-10 MPG on a full-size diesel and you won’t be surprised.
How much money per week do you spend on gas?
This varies wildly based on how much you drive. Here are some real scenarios:
Parked full-time at an RV park and just running errands — $50-$100/month. You’re barely driving.
Moving once or twice a month, 100-200 miles per move — $100-$200/month. (See our guide on How Many Miles Is Too Many When Buying a School Bus? for more on this.)
Active travelers moving every week — $400-$800/month.
Cross-country road tripping — $1,000+/month easily.
Most full-timers land in the $100-$300/month range because they’re not driving every day. The lifestyle is more about parking somewhere and enjoying it, not racking up highway miles.
160-gallon tank, 6.5 MPG — isn’t that only like 30 miles before a fill-up?
Let’s do the math. 160 gallons x 6.5 MPG = 1,040 miles on a full tank. That’s actually really solid range. You can drive from Texas to Montana on one tank.
The person asking this probably mixed up gallons and miles. At 6.5 MPG with a 160-gallon tank, a fill-up from empty costs about $640 at $4/gallon diesel. That stings. But you’re covering over 1,000 miles before you need to stop again.
Smaller buses with 60-80 gallon tanks get 300-600 miles per tank. Still enough range for most moves, but you’ll fill up more often on long trips. (See our guide on How Long Does a School Bus Engine Last? for more on this.)
The Bottom Line
- Full-size diesel skoolies: 7-10 MPG after conversion
- Short buses: 10-14 MPG after conversion
- Gas engines get worse mileage than diesel — avoid if fuel cost matters to you
- Weight kills MPG. Build light where you can.
- Most full-timers spend $100-$300/month on fuel because they’re not driving daily.
- Budget for fuel honestly — it’s your biggest ongoing cost, but it’s still cheaper than rent + car payment in most cities.
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