Clean Diesel – Diesel Technology

Older Medium-Duty Diesels Face New Calif. Regs

January 13, 2015, by Chris Brown

California fleets running medium-duty diesel trucks older than 20 years may have to replace these Class 4-6 vehicles under a set of new regulations going into effect this year.

The rules, as drafted by the California Air Resources Board (ARB), are designed to reduce emissions by bringing older diesel fleet trucks up to the cleaner 2010 engine standards. While there are separate requirements for heavy-duty Class 7 and 8 trucks, diesel trucks in the GVWR range of 14,000 lbs. to 26,000 lbs. have separate requirements.

As of Jan. 1, trucks in this GVWR range with 1995 engines or older must be replaced with trucks using 2010 engines or newer. A year from now, trucks with 1996 engines or older must be replaced, and so on. The schedule changes in 2020, when 2003 engines and older must be replaced. Starting Jan. 1, 2020 all remaining trucks would need to be replaced with 2010 model-year engines or equivalent emissions by 2023.

Heavy-duty trucks can comply with retrofit diesel particulate filters; not so for the lighter medium-duty trucks. The regulations are based on engine year, not model year, so affected trucks must undergo an entire engine replacement. In all practicality, that means replacing the truck.

Several exceptions can provide extra time to comply with the rules or even exempt certain fleet vehicles entirely.

First, fleets can delay phase-in if the affected trucks operate solely in the cleaner NOx exempt areas as designated by ARB (mainly Northern California and Central Coast counties).

Fleets can also take advantage of the "low mileage work truck phase-in option" that allows for a delay until 2020 to replace vehicles with 1996 or newer engines that travel fewer than 20,000 miles per year. Fleet must report odometer readings to CARB. This option also depends on the percentage of trucks in the fleet that comply with the 2010 rule.

To acquire an outright exemption, the older trucks must travel fewer than 5,000 miles per year (or 1,000 miles per year for out-of-state fleets operating in California) to claim the "low-use exemption" by reporting odometer readings.

There are other extensions for specific fleet applications and economic hardship. Fleets have until Jan. 31 to file to take advantage of these "flexibility options."

With proper reporting, fleets can get creative to comply with the rules, says Beth White, the manager that oversees the implementation of the bus and truck regulations for ARB. For instance, fleets can assign older trucks to low-mileage routes to satisfy the low-mileage extension or low-use exemption. Fleets that need to replace could buy used vehicles. A truck with a 2007 diesel engine isn’t due for replacement until 2023, for instance.

“Depending on the cost of the truck that’s an option that a lot of people are taking,” White says.

For more details about the regulation, including vehicles affected, percentage requirements, extensions and exemptions, visit the ARB website or call (866) 634-3735.

By Chris Brown


  1. 1. John Dutra [ January 14, 2015 @ 10:16AM ]

    I'm following this subject closely as I have a medium duty truck. Its a 1991 Isuzu gvwr of 22,500. I travel well under 20k mi per year and tried to look into the low mileage exemption after reading your article. CARB told me that the low mi. extension only applies to gvwr's greater than 26k. Brianna at CARB sent me the link she read to me from and she is correct. She did however fail to read the last critical sentence of the paragraph which states this option will be available Jan 1 2015 for light/,medium duty trucks and will be updated soon. The application date for this exemption is running out and CARB's own people don't have the info needed to initiate this exemption. I'm hoping your article is truthful and I can use this option.I'm just not at all sure how at this point. Thanks, John.

  2. 2. Nicholas [ January 15, 2015 @ 10:11AM ]

    CARB is just trying to keep our air clean for poor communities and for our children.

    It saves money in the end to scrap these old trucks and use tax credits and discounts to buy new ones that are hybrids or don't even use diesel at all.


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