CleanFUEL USA fuel system powers new Thomas propane bus
CleanFUEL USA’s liquid propane injection system is employed by the Thomas Built Buses propane Saf-T-Liner C2 school bus as well as the Freightliner Custom Chassis S2G medium-duty truck, both of which are now in full production.

The propane version of Thomas Built’s C2 uses CleanFUEL USA’s liquid propane injection system.
CleanFUEL USA’s liquid propane injection (LPI) system powers the Thomas Built Buses propane Saf-T-Liner C2 school bus as well as the Freightliner Custom Chassis S2G medium-duty truck, both of which are now in full production.
Company officials said that the CleanFUEL USA LPI fuel system is technologically advanced, fully integrated and factory installed, requiring no aftermarket modifications, for seamless integration and consistent quality. Both vehicles are EPA and California Air Resources Board certified.
“We are ecstatic that the S2G and C2 are in full production, as demand is strong in the fleet industry for propane-powered solutions that meet these two vehicles’ market needs,” said Curtis Donaldson, founder and managing director of CleanFUEL USA. “With a significant order bank and ever-increasing customer interest, the potential for both products is huge.”
The school bus and the truck are powered by an 8.0-liter, purpose-built engine by Powertrain Integration and an Allison 2300 automatic transmission with power take-off provision. The engine offers 495 ft.-lbs. of torque at 3,100 rpm and 339 horsepower at 4,100 rpm.
More Alternative Fuels

Alt-Fuel Moves: Fleets Power Up Beyond the Bus
See how districts are pairing electric buses with charging, solar, and V2G technology to cut costs, boost resilience, and unlock new fleet value.
Read More →
What the EPA’s Updated Clean School Bus Program Means for Fleet Electrification in 2026 and Beyond
A guide to the EPA’s evolving school bus grants, including how the Trump administration changed funding priorities and how school districts can prepare for future bus purchases.
Read More →A Solution Helping School Buses Charge Without Major Infrastructure Upgrades
Power Innovations International dishes on its EV charging technology designed to reduce infrastructure barriers, improve reliability, and support V2G applications for school bus fleets.
Read More →
New Eagle Launches All-in-One EV Control Platform
The new OpenECU NX3 platform integrates charging and vehicle controls into a single platform, with support for megawatt charging and vehicle-to-grid technologies.
Read More →
GreenPower Unveils New Heating Solution for Type A Bus
The all-electric bus manufacturer's new product aims to eliminate cold-cabin issues on its Nano BEAST zero-emission school buses operating in cold climates.
Read More →
Alt-Fuel Moves: Fleets Plug In for the Long Haul
School districts across the U.S. are moving electric school bus plans into operation, with new fleet deployments, charging infrastructure, and long-term electrification partnerships taking shape.
Read More →The Achilles Heel of School Bus Electrification: BetterFleet’s Take
BetterFleet’s managing partner discusses AI-powered EV fleet management, vehicle-to-grid challenges, and the real challenges in bus electrification today, from ACT Expo.
Read More →
You're On Your Own to Pick a Drivetrain [Op-Ed]
After years of federal pressure toward electric school buses, districts are suddenly being told to choose their own path. Let’s explore the risks, realities, and politics behind school bus drivetrain decisions.
Read More →Wattson: Thomas Built’s Largest EV School Bus Yet
Check in with Mark Childers on the new Wattson Type D electric school bus, featuring faster charging, expanded passenger capacity, and advanced safety technology.
Read More →The New Era of Electric School Buses: V2G, Bidirectional Chargers & More
The Mobility House discusses AI-powered charging, vehicle-to-grid technology, smart energy management, and the next phase of school bus electrification.
Read More →
