Tier 4, however updated, has been in effect for some time. The most recent update, passed in March of this year and phases in model years 2027- 2023. With respect to trucks (light, medium and heavy duty)...You do realize this is rolling out to the entire country in tiers right? It's not just California. Trucks are going up by $25K-$30K starting Jan 1, 2026 and it will only go up from there.
"Even though several provisions of the Tier 4 program are aligned with the California LEV IV standards, there are two sets of standards thar differ in many important respects. One example difference is the final LEV IV fleet-average NMOG+NOx emission limit that remains at the LEV III/Tier 3 level of 30 mg/mi, while the California standards limit the manufacturers’ ability to include zero emission vehicles (ZEV) in their fleet average NMOG+NOx calculation."
So standards, depending on the state you live in, are not all beholden to being the same as California.
Again, let them starve.