Most of the traditional school buses of today run on diesel engines, which generally get better gas mileage than their gasoline counterparts. But buses aren’t small vehicles and when they are loaded up with kids or are converted into skoolies, miles-per-gallon takes a hit.

There are several different types of buses out there. A standard, long school bus, which is the most common, gets an average of 4 or 5 mpg, while a smaller bus will get around 6 mpg and a special needs bus around 3 or 4 mpg.

That sounds absolutely terrible, but you should remember that these numbers are culled from thousands of buses across the country, many of which have high mileage and spend the majority of their routes in stop-and-go traffic.

School bus engines and mpg

When it comes to school bus mpg, the data is kind of all over the place, for reasons stated above. Some school districts have less money to spend than others as well, which will make a difference in how often older school buses are auctioned off and replaced by new ones.

There are plenty of claims out there that brand new school buses with Cummins 5.9 engines can pull 23.9 mpg. Flip the page, and you’ll find another article that claims they get 10 mpg. That’s a huge disparity.

One thing is certain, most agree that the Cummins 5.9 combined with the Allison 643 transmission are tops in fuel mileage. The typical school bus, Cummins 5.9 or not, travels 250,000 miles and is serviced every 12,000 miles throughout its service life.

Cummins ISB engines are also worth taking note of, as they are supposedly better than the Cummins 5.9s. While the jury is still out on that one, it's worth considering if you’re in the market for a school bus.

Chassis and Engine Miles Per Gallon/Average
Chevy 6L V8 13 mpg
GMC 6L V8 13 mpg
Ford V10 11 mpg
Duramax 8L V8 14 mpg
Ford 6L 13 mpg
Ford 7.3L 14 mpg
Chevy 6.2L V8 13 mpg
Chevy 6L Turbo-Diesel V8 14 mpg
Ford 460 V8 14 mpg

Keep in mind, these stats exist in a bubble. In other words, it's the fuel efficiency you would get brand new, with zero negative-operating conditions. That’s why you don’t see school bus mpg averages that high.

The small, special needs buses usually get lower mpg than their larger cousins, mostly because they are equipped with a large truck or van engines that are converted over for bus use.

Since 91% of all school buses in the country run on diesel engines, there is a good deal of longevity to be expected as well. That’s also why retired school buses are purchased by those willing to convert them into skoolies.

How many gallons of fuel do school buses use?

school bus parked in front of fence

Depending on the size of the bus, a fuel tank will be between 40 gallons and 200 gallons. According to Bus Foundation, a typical school bus will burn through 1,700 gallons per year, even though many are not in use through the summer period.

Of course, this accounts for field trips and the team traveling for football, baseball, basketball, gymnastics, track and field, soccer, softball, cheerleading, and many other competitive sports that schools participate in and compete in.

That’s a lot of fuel. It's also the reason that states and the federal government have all determined that diesel engines are the best engines for school buses across the country. A gasoline engine in a school bus will last about 3 years before the duress of stop-and-go traffic permanently retires it.

Diesel engines, on the other hand, will easily last 1 to 15 years. Before it needs to be replaced or the school bus is sold or auctioned off. New buses are far more fuel efficient than older ones, and age affects the fuel consumption rate as the years crawl by.

Improving the fuel mileage of a school bus or skoolie

If you are thinking about purchasing a school bus to convert into a skoolie, you might be disappointed at the low fuel mileage they get, regardless of the size it would seem. Fortunately, there are some ways that you can minimize the mpg problem:

  • Only purchase a school bus with a diesel engine, not gasoline
  • How you drive the bus matters
  • Change the aerodynamics
  • Size and weight affect mpg
  • Standard and preventative maintenance
  • Get some better tires

You will likely never have the chance to purchase a school bus that runs on gasoline mostly because they are so hard to find. That’s something you won’t have to worry about. However, if you come across a school bus with a gasoline engine, stay away from it.

How Much Does a Used School Bus Cost?
Considering purchasing a used school bus and converting it into a full-blown skoolie and cruise down the coast of California? Here’s how much a used school bus costs.

Driving a bus

How you drive the bus, whether you have converted it yet or not, matters. If you have a heavy foot or get yourself caught up in stop-and-go traffic a lot, you’ll burn through that fuel quickly.

The average cost of diesel per gallon is roughly $5.70/gallon right now. That means a 100-gallon tank will cost you $570 to fill up. Don’t waste all that money because you want to try and drag race every time a red light turns green.

Alter the aerodynamics

Back in August of 2012, a teenager named Jonny Cohen came up with an ingenious method for reducing the aerodynamic drag on school buses. Jonny got together with a few friends and created the Greenshields Project.

This project resulted in a “GreenShield” device on the top of the bus, which reduced drag and ended up improving the fuel economy by 10% to 20%. The point is if you are converting a school bus into a skoolie, aerodynamics matter a lot more than you might think.

Size and weight

Another thing to consider is the weight and size of a conversion. A school bus is what it is while it is in public service. While the GreenShield clearly helped school buses in Illinois, it's not something that has been adapted across the country just yet.

Converting a school bus into a skoolie is a fun, if expensive, DIY project. During the process, you should consider how much weight you are taking off and how much you are adding back on. It will make a huge difference in the long run. This is especially true since most skoolie conversions are already running off of engines with a quarter of a million miles on them.

How Much Does a School Bus Weigh?
Knowing how much a school bus weighs is great if you’re considering converting it into a full-blown RV. Let’s take a closer look at what you can expect in terms of weight.

Standard and preventative maintenance

You will keep your fuel mileage under control by focusing on basic maintenance, much of which is also preventative. Changing the oil regularly, keeping the tire pressure at the correct level, and changing your other fluids at the recommended mileage will keep your mpg in top shape.

Adding or changing out specific components will improve your fuel mileage as well. Installing an idle-stop system and cleaning or installing an improved fuel injection system will decrease fuel consumption.

Low-rolling resistance tires

Because standard tires are garbage. Honestly, you’re going to be spending a ton of money to replace the tires anyway, so you may as well go with some low-rolling resistance tires.

Of course, if you can’t keep your tires inflated properly it doesn’t matter if you have the best tires in the world or circular stone slabs from the Flinstones—your fuel mileage will suffer.

How Many Wheels Does a School Bus Have?
You’ve undoubtedly seen one of those long, yellow school busses if you’re living in the states. But have you ever noticed how many wheels they have? Here’s the answer.

School buses are simply not very fuel efficient

three yellow school buses in a parking lot

We can wax poetically all day about the amazing 12 miles per gallon that ‘such and such’ got out of his or her new skoolie. But, the reality is, that fuel mileage in a school bus is truly terrible. All you can do is struggle to minimize it to the best of your ability.

That means keeping the school bus at or under the speed limit and taking good care of it. While scientists in a laboratory come up with ways to replace diesel engines with propane tanks to improve the miles per gallon from 6 miles to 6.5 miles, you should focus on proper maintenance.

On the bright side, propane is showing some signs of value, especially since it ever so slightly improves fuel mileage while not emitting nearly as many pollutants into the atmosphere.  

We’re a long way from propane school buses just yet. Besides, someone will have to convince the world why an impacted propane tank, in the event of an accident, is safer than a diesel fuel tank with 40 kids sitting on top of it.

Final thoughts

Miles per gallon in diesel engine school buses are averaging 4 or 5 across the United State’s fleet of around 500,000. It's not the best in the world. But, if you are looking to convert a school bus into a skoolie, there are some things that you can do in the maintenance department to improve that somewhat.

Until we replace all school buses with some future technology, however, it's safe to say that you’re not going to get a ton of miles per gallon any time soon.