Fuel Fact Check: School Buses
Claim: Diesel is comparable or even cleaner than other fuel types.
School bus operators have options when it comes to clean fuel. With modern emission technology, diesel has come a long way toward tailpipe improvement and has made major strides in reducing harmful outputs. However, upon further investigation, even with the cutting edge of diesel emission technology, there are challenges both environmentally and operationally.
While today’s diesel vehicles are significantly cleaner than years past, they accomplish this through significantly more complexity. Today’s diesels require expensive components, high-maintenance systems and complex emissions software that aren’t required for a propane vehicle. Without more than 15 ancillary devices, diesel engines wouldn’t be able to meet EPA emission standards. That’s 15 components that need to be maintained, including diesel particulate filters, EGR coolers, DEF injection systems and other complex after-treatment devices.
Propane autogas is naturally much cleaner than diesel in composition and in combustion. This cleanliness yields benefits like less particulate and suspended carbon contaminating the engine oil jacket, which in turn helps to reduce maintenance burdens.
For example, an oil change for a Blue Bird Vision Propane bus uses about seven quarts compared with 25 to 30 quarts for a typical diesel engine. A diesel oil filter itself costs two to three times more than a propane autogas oil filter. Nowadays, diesel has become so complex that diesel mechanics need special training and skills – propane mechanics don’t need that training.
And consider engine noise level. Diesel produces noticeable engine noise, which is related to the high-compression design of the engine. Propane vehicles, which follow a strategy more aligned with gasoline engines, operating about 50% more quietly than diesel.
Propane autogas is a non-toxic, non-carcinogenic and non-corrosive fuel classified as a non-contaminant by the EPA. Each day, more than 1.1 million students across the U.S. ride to school in propane school buses. Those buses emit fewer greenhouse gases, smog-producing hydrocarbons, nitrogen oxides and particulate emissions than conventional fuels. Additionally, their fuel tanks are 20 times more puncture-resistant than diesel tanks and can withstand four times the pressure.
School bus operators look to propane school buses to lower their total cost of ownership, including the cost of fuel and maintenance. Propane offers a readily available, affordable and uncomplicated solution to eliminate emissions.
Bottom line? Today’s diesel engines must certify to the same federal standards that all fuels are measured against – but at what cost? Fortunately, propane does not require any costly and complex after-treatment.
Ryan Zic is vice president of sales – school bus for ROUSH CleanTech. His expertise includes direct sales, original equipment manufacturer management and Tier 1 sales and support. He can be reached at ryan.zic@roush.com.
