Diesel vs. Gas Trucks: Which Is Better for the Environment?

There’s no one-size-fits-all winner: for most light-duty trucks driven in cities, gasoline engines generally have lower local air-pollution impacts, while for long-distance, heavy-load driving, modern diesels typically produce slightly lower greenhouse-gas emissions per mile. The cleanest overall choice, where practical, is a zero-emission truck (battery-electric) or pairing efficient powertrains with low-carbon fuels.

What “better for the environment” really means

Environmental performance covers two broad categories. First are climate impacts—mainly carbon dioxide and other greenhouse gases (GHGs). Second are local air pollutants that harm health, especially nitrogen oxides (NOx) and fine particulate matter (PM). Diesel and gasoline trucks perform differently across these metrics, and results vary with how and where the truck is used.

Greenhouse gases (CO2e) and fuel efficiency

Diesel fuel contains more carbon per gallon than gasoline (about 10.16 kg CO2/gal for diesel vs. 8.89 kg CO2/gal for gasoline). However, diesel engines are more efficient, especially at steady speeds and under load. In real-world pickup use, that efficiency often offsets diesel’s higher carbon content:

For a typical full-size pickup, highway fuel economy might be about 22 mpg (diesel) vs. 17 mpg (gasoline). That translates to roughly 0.46 kg CO2 per mile for diesel and 0.52 kg for gasoline—an advantage of about 10–15% for diesel. Under heavy towing, diesel’s advantage can widen somewhat. In city driving with frequent cold starts and idling, the gap can narrow.

Upstream emissions (from producing and transporting fuel) also matter. Differences between conventional gasoline and petroleum diesel are modest, but the choice of alternative or renewable fuels can be consequential (see “Lifecycle and fuel choices”).

Smog-forming and health pollutants

Modern emissions controls sharply reduce both gasoline and diesel pollution, but their profiles differ. Gasoline trucks with three-way catalytic converters emit very low NOx when warmed up and driven normally. Diesel trucks rely on diesel particulate filters (DPF) to capture soot and selective catalytic reduction (SCR) using diesel exhaust fluid (DEF) to cut NOx. When these systems are working and hot, pollutant levels are very low. Challenges arise in short-trip, cold-weather, and stop‑and‑go use, where diesels can show higher NOx spikes before aftertreatment fully lights off or during DPF regeneration. Gasoline direct-injection engines can emit fine particles, but increasingly stringent standards have pushed manufacturers to manage those emissions, sometimes with gasoline particulate filters.

Bottom line: for urban and suburban driving with frequent short trips, gasoline trucks typically impose less local air-quality burden than diesels. For highway-heavy duty cycles, the gap in local pollutants narrows and can be minimal for well-maintained modern diesels.

Noise and other considerations

Diesels are often louder at idle and under load, though cabin sound insulation has improved. Odor and visible smoke should be negligible in any compliant, well-maintained modern diesel with an intact DPF; issues often indicate malfunction or tampering. Proper maintenance is critical for both fuel types to sustain low emissions over time.

What current U.S. rules mean for future trucks

Stricter standards are pushing down both climate and health pollutants across all truck types. Two federal actions are particularly relevant in the U.S.:

The list below highlights recent federal rules that affect diesel and gasoline truck emissions and may influence your future choices.

• Heavy-duty NOx and durability standards (EPA “Cleaner Trucks Plan,” finalized Dec 2022): Starting with Model Year (MY) 2027, on-road heavy-duty engines must cut NOx by roughly 80% vs. today’s levels and meet tougher durability requirements—meaning cleaner performance over longer lifespans, especially in low-speed and idle conditions.
• Heavy-duty GHG Phase 3 standards (finalized March 2024): For MY 2027–2032 heavy-duty vehicles, manufacturers must meet progressively tighter CO2 targets, accelerating efficiency improvements and the shift toward zero-emission trucks in certain segments.
• Light-duty/tailpipe standards (Tier 3/Tailpipe and multi-pollutant rules): Passenger vehicles and light-duty pickups have stringent limits on NOx and PM and increasingly tight fleet-average CO2 targets through 2032, which is pushing more efficient gasoline powertrains, hybrids, and battery-electric options.

As these rules phase in, both diesel and gasoline trucks will become cleaner. The biggest changes will be in heavy-duty diesels operating in urban areas, where low-speed NOx has been a stubborn problem; starting in 2027, engines are engineered to control NOx much more effectively during idling and stop‑start use.

Real-world use cases: Which fits your duty cycle?

Your driving pattern is often the decisive factor. Consider how you’ll actually use the truck—speed, load, climate, and trip length strongly influence emissions and efficiency.

The following scenarios illustrate where each engine type tends to be environmentally preferable.

• Mostly city, short trips, light loads: Gasoline usually has the edge for local air quality; diesels may struggle to keep aftertreatment hot and can require DPF regens.
• Frequent highway driving, long distances, steady speeds: Diesel tends to deliver lower CO2 per mile and excellent fuel economy, with aftertreatment operating efficiently.
• Regular heavy towing or hauling: Diesel’s torque and efficiency under load typically reduce fuel use and CO2 compared with a similar gasoline truck.
• Cold climates with many short drives: Gasoline often remains cleaner locally; diesel aftertreatment warm-up can lag, and idling to warm up is emissions-intensive.
• Stop‑and‑go commercial use with extended idling: Post-2027 low-NOx diesels will be much improved, but today a well-tuned gasoline or a hybrid (or, where feasible, an electric truck) may minimize local pollution.
• Access to low-carbon fuels or charging: If renewable diesel is readily available, a diesel can be very competitive on lifecycle GHG. If you can reliably charge, a battery-electric truck can minimize both local and lifecycle emissions.

Match the engine to the duty cycle: the more your use leans toward highway miles and heavy loads, the stronger diesel’s GHG case; the more your use is urban, short-trip, and cold-start heavy, the stronger gasoline’s local-air-quality case.

Lifecycle and fuel choices that change the math

The carbon intensity of the energy you put into the truck can outweigh engine-type differences. Availability varies by region, but these options can materially cut lifecycle emissions.

Here are common fuel pathways and their typical environmental impacts.

• Renewable diesel (R99/RD): Chemically similar to diesel; drop-in compatible. Depending on feedstock, lifecycle GHG can be roughly 50–70% lower than petroleum diesel. Increasingly available on the U.S. West Coast due to Low Carbon Fuel Standards.
• Biodiesel blends (e.g., B20): Can reduce lifecycle GHG roughly 10–20% at B20 (and much more at higher blends), with modern SCR systems managing any small NOx changes. Check manufacturer guidance for blend limits and cold-weather performance.
• Ethanol blends (E10–E15): Most U.S. gasoline already contains ethanol. Lifecycle GHG can be lower than neat gasoline depending on production methods, though per-mile reductions are smaller than nominal per-gallon values due to energy content.
• Electricity (for battery-electric trucks): Zero tailpipe emissions; lifecycle GHG depends on the grid mix. In most U.S. regions today, total GHG is lower than comparable combustion trucks, with the gap widening as the grid adds renewables.

If you can access low-carbon fuels or electricity, those choices often deliver larger climate benefits than switching between gasoline and diesel alone. Always verify compatibility and warranties when using alternative liquid fuels.

Practical ways to reduce your truck’s footprint now

Regardless of engine type, careful operation and maintenance cut both GHGs and local pollutants.

• Right-size the truck and engine for your actual needs; avoid unnecessary weight and oversized tires.
• Keep emissions systems intact and maintained; use DEF as specified for diesels, and never tamper with DPF/SCR or catalytic converters.
• Minimize idling and aggressive acceleration; plan routes to reduce congestion and cold starts.
• Maintain tire pressure and alignment; consider low-rolling-resistance tires.
• Use manufacturer-recommended oil and filters; address check-engine lights promptly.
• Choose cleaner energy where available: renewable diesel or appropriate biodiesel blends for diesels; top-tier gasoline and, when feasible, consider hybrid or electric models.

These steps often save money on fuel and repairs while delivering measurable environmental gains—small changes add up over thousands of miles.

Bottom line

If your truck’s life is mostly city errands and short trips, a gasoline engine generally imposes less local air-pollution harm. If you cover long highway miles or tow heavy loads, a modern diesel can deliver lower CO2 per mile and competitive local emissions when properly maintained. Looking ahead, tighter U.S. standards from 2027 onward will make both options cleaner, and the biggest environmental gains come from zero-emission trucks or pairing efficient powertrains with low-carbon fuels.

Summary

Neither diesel nor gasoline trucks are universally greener. Gasoline is typically cleaner for local air quality in urban, short-trip use. Diesel often wins on greenhouse gases for long-distance, heavy-duty work thanks to higher efficiency, especially with access to renewable diesel. Maintenance, duty cycle, climate, and fuel or charging availability are decisive. Where feasible, battery-electric trucks deliver the lowest overall emissions today and will improve as the grid decarbonizes.

Are diesels environmentally friendly?

While diesel cars offered lower CO2 emissions, the engines at the time emitted vastly larger quantities of other pollutants contributing to poor local air quality and health issues. These included nitrogen oxides (NOx) and particulate matter.

What is the most environmentally friendly engine?

Hydrogen and ammonia engines offer almost zero emissions, so they could enter clean transportation zones, for example. Other solutions rely on advanced technologies to increase efficiency and reduce emissions, making them increasingly competitive with electric vehicles.

What is worse for the environment, gas or diesel?

Unlike their gasoline counterparts, diesel engines emit higher levels of nitrogen oxides (NOx) and particulate matter. These pollutants, notorious contributors to air pollution, can have detrimental effects on both human health and the environment.

What are the disadvantages of a diesel truck?

Disadvantages of a diesel truck include a high initial purchase cost, increased maintenance and repair expenses, a rougher and noisier ride, difficulty starting in cold weather, and environmental concerns due to higher emissions. They can also be less efficient with light loads, have a limited availability of fuel in some areas, and may not be ideal for daily driving without frequent heavy hauling. 
Higher Costs

• Purchase Price: Opens in new tabDiesel trucks typically have a higher upfront cost than gasoline models due to their more complex and robust components. 
• Maintenance: Opens in new tabDiesel engines are more expensive to repair and maintain, requiring specialized tools and knowledge. 
• Fuel Price: Opens in new tabDiesel fuel is often pricier than gasoline, and filling the tank can be very expensive. 

Performance and Ride

• Rougher Ride: The engine’s design and power delivery can result in a noisier and more rugged ride compared to gasoline vehicles. 
• Cold Weather Starting: Diesel engines can be more difficult to start in cold weather conditions. 
• Inefficiency with Light Loads: For lighter loads, a diesel engine’s high torque may be less efficient than a gasoline engine’s higher horsepower and lower torque. 

Environmental Impact 

• Higher Emissions: Diesel engines produce higher levels of harmful emissions and soot, contributing more significantly to air pollution and potential environmental harm.

Practical Considerations

• Fuel Availability: Opens in new tabWhile available, diesel fuel isn’t as universally available as gasoline, which can be a drawback in rural or remote areas. 
• Daily Driving: Opens in new tabDiesel trucks can be large, heavy, and generally ill-suited for daily driving when not used for their primary purpose of heavy towing or hauling. 
• Specialized Use: Opens in new tabThey are best suited for heavy-duty use and may not be the right choice if you only have light loads or don’t plan to tow frequently, as you may not recoup the higher initial investment.