In farm years, a 12-year-old engine is often not even broken in on many dairy farms.

That really doesn’t matter to legislators and regulators in California, though.

It’s now illegal to drive a great many semi-tractor trailers that can roll down highways in America’s 49 other states. Effective January 2023, diesel-fueled vehicles model years 2010 and older, with a gross vehicle weight rating of 14,000-pounds or greater, are banned from the Golden State’s highways.

To put teeth into the laws and regulations, the State of California Department of Motor Vehicles will refuse registration, renewal, or transfer of diesel-fueled vehicles in the aforementioned category. That’s just the start. Annual fleet audits will take place and those owners that aren’t in compliance will face fines and a complete hold on all Department of Motor Vehicle registrations.

There’s a small reprieve for some pre-2010 diesel truck owners. If one can document the truck did not exceed 1,000 miles throughout the year, the truck may be registered and remain on roadways. However, those owners must participate in California’s Heavy Duty Inspection and Maintenance program. Keep in mind, 1,000 miles per year equates to under 3 miles per day.

Part of a larger law

California’s ambitious plan took root in 2008 when the California Air Resources board approved legislation to curb emissions from old trucks and busses. Hence, many owners initially had to install diesel exhaust filters. Then came the bans on old engines. Starting back in 2020, the rolling ban began by culling vehicles made in 2000 and before.

The cascade continued until this January, when the 2010 and older trucks met the chopping block. It's been estimated that the 2023 culling activity involving 2010 and older diesel engines impacted some 200,000 buses and over 70,000 semi tractors.

The story will enter a new chapter in 2035 when California law will ban all diesel engines in these size categories.