U.S. imports of parts for compression-ignition (diesel) internal combustion piston engines (non-aircraft) (HS 840999) totaled $376.0M in August 2026, imported from 97 countries.
Importers of Parts for Compression-Ignition (Diesel) Internal Combustion Piston Engines (Non-Aircraft) paid $50.4M in duties in August 2026, an effective tariff rate of 13.40% of the $376.0M imported — duty actually collected as a share of that value, not the published tariff schedule. Parts for Compression-Ignition (Diesel) Internal Combustion Piston Engines (Non-Aircraft) imports of $376.0M in August 2026 ran 11% above the year-to-date monthly average of $337.7M.
Last updated: August 2026 dataServing the heavy-duty diesel aftermarket and OEM supply chains, this heading covers components — cast-iron pistons, connecting rods, and general parts — for diesel engines used in road vehicles, marine propulsion, and other applications. Mexico and Germany lead US imports, reflecting both nearshore automotive manufacturing and Germany's strong position in commercial-vehicle diesel technology. China is also a significant source, making Section 301 tariff exposure a live concern for procurement teams sourcing diesel parts across multiple origins. The schedule's end-use tiers (road, marine, NESOI) mirror those for spark-ignition parts under 840991, so consistent classification methodology across both headings is important for importers handling mixed engine-parts shipments.
AI-written summary of the official U.S. Census Bureau trade figures on this page — verify before relying on it.
16.3K shipments/mo
Lines such as 8409994000 are reserved for parts specifically designed for diesel engines powering road tractors, buses, automobiles, and trucks. Parts for stationary power generation, agricultural equipment, or other non-road, non-marine applications fall into the residual NESOI line (8409998000). The end-use of the engine — not the part in isolation — governs which line applies.
Origin matters significantly here. Parts from China may carry Section 301 additional duties, while parts from Mexico may qualify for preferential treatment under USMCA if they meet applicable rules of origin. Germany-origin parts enter under standard MFN rates without a preferential program currently in force between the US and the EU. Importers should conduct an origin analysis for each supplier before committing to a sourcing strategy.
HSChapter 84
Subheading 2 of 3 in heading 8409
Subheading 840999 · $376.0M of $1.1B
ImportsExports
Imports
$376.0MYoY · free account
Exports
$221.7MYoY · free account
12-mo low · imports
YoY · free accountOver the twelve months to August 2026, the U.S. imported $3.8B of Parts for Compression-Ignition (Diesel) Internal Combustion Piston Engines (Non-Aircraft).
Through August 2026. Source: U.S. Census Bureau.
Trade Directory
List your company under HS 840999 — Parts for Compression-Ignition (Diesel) Internal Combustion Piston Engines (Non-Aircraft), so the companies trading it can find you. Be the first supplier listed.
HS10 import codes under this HS6 parent, each with its own page. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Import Value | Effective Tariff % | Dutiable Share | Duty Collected |
|---|---|---|---|---|---|
| 8409999190 | Parts Fr Comp-Ig Pst Eng Fr Rd Tr,Bus,Auto,Trucks | $190.8M | 13.48% | 75.50% | $25.7M |
| 8409999990 | Parts for Comp-Ig Int Comb Pst Engines, NESOI | $120.1M | 13.19% | 73.63% | $15.8M |
| 8409991040 | Cst Trn F Comp-Ig Pst Eng for Rd Tr,Bus,Auto,Truck | $16.1M | 16.71% | 69.97% | $2.7M |
| 8409999110 | Conn Rods for Comp-Ig Pst Eng Fr Rd Tr,Bus,Auto,Tk | $13.9M | 12.00% | 42.32% | $1.7M |
| 8409999290 | Parts for Comp-Ig Int Comb Pst Eng for Marine Prop | $12.9M | 8.37% | 76.38% | $1.1M |
| 8409991080 | Cast-Iron Pst for Comp-Ignition Pst Eng, NESOI | $11.5M | 22.36% | 94.49% | $2.6M |
| 8409999910 | Conn Rods for Comp-Ig Int Comb Pst Eng, NESOI | $8.5M | 8.94% | 51.51% | $756K |
| 8409991060 | Cast-Iron Pst for Comp-Ignition Pst Eng for Marine | $2.1M | 1.79% | 13.75% | $37K |
| 8409999210 | Conn Rods for Comp-Ig Pst Eng for Marine Propulsn | $65K | 6.34% | 63.42% | $4K |
HS10 export codes under this HS6 parent, each with its own page. Source: U.S. Schedule B export classification.
| Code | Description | Export Value |
|---|---|---|
| 8409998000 | Parts for Diesel Engines, NESOI | $109.0M |
| 8409994000 | Parts F Diesel Eng F Road Tr, Bus, Auto, Truck | $101.2M |
| 8409996000 | Parts for Diesel Engines for Marine Propulsion | $11.5M |
Import lines come from the U.S. Harmonized Tariff Schedule and export lines from Schedule B. The two are numbered by different agencies, so the same 10-digit code can appear in both tables describing a different product.
Imports · August 2026
origin
Mexico and Germany together supply 46% of it. China pays 36.5% duty; Mexico 2.1%.
customs district
destination
entry
rate provision · imports
28.3% enters free of duty; duty collected equals 13.40% of total import value.