Diesel currently averages $5.26 per gallon against $4.01 for regular gasoline — a $1.25 premium (EIA, week of 2026-08-10). The gap is structural: cleaner-fuel rules, higher tax, and industrial demand. Here's the full comparison.
| Gasoline | Diesel | |
|---|---|---|
| US average price (this week) | 4.01 | 5.26 |
| Energy per gallon | ≈120,000 Btu | ≈137,000 Btu (+12%) |
| Engine ignition | Spark | Compression |
| Typical efficiency | Baseline | 20–35% better MPG |
| Federal tax | 18.4¢ | 24.4¢ |
| Futures benchmark | RBOB (NYMEX RB) | Heating Oil (NYMEX HO) |
| Winter behavior | Cheaper winter blend | Competes with heating oil — spread widens |
Price history for both fuels: gasoline by year · diesel by year. Current state-level prices: gas · diesel.
Diesel averages $5.26 per gallon versus $4.01 for regular gasoline (EIA, week of 2026-08-10) — a gap of $1.25. The spread widens in winter, when diesel competes with heating oil for the same refinery output.
Three structural reasons: US diesel must be ultra-low-sulfur (costlier to refine), federal tax is 6 cents higher (24.4¢ vs 18.4¢), and diesel faces relentless demand from trucking, farming, industry — and, in winter, home heating. Before 2005 diesel was usually the cheaper fuel; the sulfur rules and global demand flipped it.
Yes — typically 20–35% better fuel economy. Diesel fuel carries about 12% more energy per gallon, and compression-ignition engines convert it more efficiently, especially under load. That's why trucking is diesel: at highway load a diesel semi does work no gasoline engine could do economically.
Diesel and heating oil are essentially the same middle-distillate product, so a cold Northeast winter puts trucks and furnaces in competition for the same barrels. Distillate inventories heading into winter (published in the weekly EIA report) are the number to watch.