Yes—heavy-duty diesel efficiency can be improved dramatically by 2035. With engine upgrades, hybrids, aerodynamics, and smart controls, fuel economy boosts of 30–45% are achievable—and even higher in certain applications when including advanced systems like hydraulic hybrids or waste heat recovery.
Here’s what research and industry roadmaps show about how much efficiency improvement heavy-duty diesel vehicles (HDDVs) can achieve through model year 2035:
What Efficiency Gains Are Technically Possible by 2035?
A comprehensive study by the International Council on Clean Transportation (ICCT) outlines the potential efficiency gains by calendar year 2035 for heavy-duty diesel trucks in the U.S.:
- Class 8 tractor-trailers could see up to 29% better fuel economy and 24% lower CO₂ emissions per ton-mile compared to Phase 2 standards (effective through model year 2027), at a cost of around $5,200 per vehicle.
- Adding mild hybridization, plus transmission strategies like down-speeding and downsizing, could lift total improvements to ~39% fuel economy gains, though with higher cost ($29,300) and longer payback times.
- Class 6–7 vocational trucks show even stronger potential: up to 44% better fuel economy and 34% reduced CO₂ emissions compared to Phase 2, at a marginal cost of ~$15,400 and payback under two years.
Key Technologies Driving These Gains
Several proven and emerging technologies contribute to these improvements:
- Engine Efficiency Enhancements: Higher thermal efficiency via better combustion, friction reduction, and aftertreatment optimization remains central.
- Aerodynamics: Improvements like streamlined cabs, sealed joints, camera-based mirror systems (vs. traditional mirrors), and vehicle-lowering systems at speed reduce drag significantly. Volvo’s recent models have integrated such features with cumulative fuel benefits.
- Hybridization (Mild & Hydraulic):
- Mild hybrids with down-speeding and engine optimization can add ~10 percentage points of additional fuel economy gain on top of baseline improvements.
- Hydraulic hybrids, particularly for stop-and-go applications like refuse trucks or buses, can boost fuel economy by 60–70%, with >40% cuts in CO₂ emissions.
- Waste Heat Recovery: Rankine-cycle systems can recycle exhaust heat, with potential fuel savings from 6% to over 30%, depending on driving patterns.
- Thermoelectric Generators (TEGs): Still nascent, but they can convert exhaust heat into electricity, reducing engine load and saving fuel.
- Advanced Combustion & Controls: Technologies like variable valve actuation (VVA), cylinder deactivation, and digital/AI controls help balance emissions and efficiency. Purdue research shows these can cut emissions without efficiency penalties.
- Low-Carbon Fuels & Materials: Use of renewable diesels (HVO, biodiesel blends) and lightweight, high-rigidity materials (e.g., compacted graphite iron) offer efficiency and emissions gains. FPT’s XC13 engine boasts up to 7% lower fuel consumption along with reduced weight and better torque.
- Platooning & Eco-Driving: Coordinated truck platooning could cut fuel use by ~10%, while eco-driving strategies (e.g., predictive cruise control) deliver real-world savings of 13–26% in some cases.
Overall Outlook by 2035
- Aggregate improvements of 25–45% in fuel economy for conventional heavy-duty diesel trucks seem feasible and cost-effective for both tractor-trailers and vocational vehicles.
- Achieving these gains will require an integrated package: engine upgrades + aerodynamics + hybrid systems + advanced controls + alternative fuels.
- Hybridization and waste heat recovery offer particularly large upside in fuel-heavy applications.
- Platooning and eco-driving tools add operational-level boost outside pure hardware upgrades.
Summary Table
| Segment / Tech Focus | Potential Fuel Economy Gain by 2035 |
|---|---|
| Class 8 Trucks | ~29% (baseline improvements) |
| Class 8 + Mild Hybrids | ~39% |
| Class 6–7 Trucks | Up to 44% |
| Hydraulic Hybrid Systems | +60–70% in urban cycles |
| Waste Heat Recovery | ~6–30% depending on driving |
| Platooning / Eco-driving | ~10–26% |
| Renewable Fuels + Materials | Embedded within engine gains |
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