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

The Fuel Budget You Can Actually Predict: How Propane Autogas Keeps Money in the Classroom
Learn how propane autogas helps school districts manage fuel costs with predictable pricing, lower maintenance, and reduced emissions from former transportation director Joel Stutheit.
Read More →
Hendrickson, Driventic Introduce New Electric Powertrain for School Buses
ELECTRAAX, the electrified, lightweight drive axle offers integrated ePowertrain efficiency and modular flexibility for Class 6–7 school bus use.
Read More →
The Mobility House Joins PowerFlex in Fleet Electrification Deal
The acquisition combines intelligent charging software, bidirectional charging expertise, and fleet electrification services to support the growing adoption of electric school buses across North America.
Read More →
Alt-Fuel Moves: Electric School Bus Investments Hit the Road
See which districts across the U.S. are putting electric school buses into service, expanding charging infrastructure, and planning the next phase of fleet electrification.
Read More →
With Fuel Volatility Ahead, School Districts Turn to Propane
While diesel prices peaked above $5 this spring, districts with propane autogas-powered fleets paid under $2 per gallon, according to PERC.
Read More →
EPA Unveils Proposed Changes to 2027 Heavy-Duty Engine Rules
The federal agency has proposed changes to next year’s targets that would eliminate DEF derates, ease warranty requirements, and retain current NOx emissions standards.
Read More →
Alt-Fuel Moves: EV Charging & Infrastructure Projects Gain Momentum
The latest developments include new funding, charging infrastructure, utility investments, and fleet technologies designed to support the transition to electric school buses nationwide.
Read More →
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 →
