If you've ever fueled in Texas at $3.40 then crossed into California and paid $4.94, you weren't imagining it. As of the EIA's May 5 report, the spread between PADD 3 (Gulf Coast) and California is $1.53/gallon. On a 100-gallon fill, that's $153 difference. Same diesel? Not exactly. Here's the breakdown.

1. Fuel specifications add 10-25 cents/gallon

California, Oregon, and Washington require CARB diesel — California Air Resources Board ultra-low sulfur diesel with stricter aromatics, cetane, and sulfur limits than federal ULSD. It costs more to refine, requires segregated handling at terminals, and can't be moved freely across state lines.

The CARB premium is typically 10-25 cents/gallon depending on production cycles. New York and a few Northeast markets also have their own specs that add a smaller premium.

2. State and local fuel taxes add 30-65 cents/gallon

Federal diesel tax is a flat 24.4 cents/gallon everywhere. The variable is state and local.

Approximate state diesel tax in 2026:

  • California: ~95 cents/gal (state + carbon programs + sales tax)
  • Pennsylvania: ~75 cents/gal
  • Washington: ~50 cents/gal (plus carbon program adders)
  • New York: ~45 cents/gal
  • Texas: ~24 cents/gal
  • Louisiana: ~22 cents/gal
  • Mississippi: ~22 cents/gal

That's a 70+ cent gap between high-tax states and low-tax states before you factor in anything else.

3. Refinery geography adds 10-30 cents/gallon

PADD 3 (Gulf Coast) hosts roughly 45% of U.S. refining capacity. PADD 5 (West Coast) hosts about 9%. Refining is a fixed-asset business — concentration drives lower marginal cost where capacity is dense.

The Gulf Coast also exports diesel internationally, meaning when global distillate demand softens, regional supply gets long and prices fall fast. The West Coast runs closer to balance most weeks; any refinery hiccup spikes prices because there's nowhere to source incremental supply from cheaply.

4. Pipeline access adds 5-15 cents/gallon

The Gulf Coast feeds the Midwest and East Coast through the Colonial Pipeline (5,500 miles). The Plains and Rocky Mountain regions get partial pipeline coverage. The West Coast is essentially pipeline-isolated from Gulf production — diesel arrives by tanker (Jones Act flagged, expensive) or rail.

Limited inbound logistics means West Coast retail can't arbitrage down to Gulf prices even when the spread gets unusually wide.

What this means for routing

If you have any flex on where you fuel, the regional spread is real money:

  • A coast-to-coast run fueling 200 gallons in PADD 3 instead of PADD 5 saves roughly $300 per round trip.
  • Running through PADD 4 (Rocky Mountain) instead of detouring into California for a load saves 30-50 cents/gallon.
  • The Gulf Coast / Lower Atlantic corridor is the cheapest sustained operating region in the country. Drivers running OTR Texas-to-Florida pay materially less for fuel than anyone else.

What this means for fuel cards

Card networks publish per-station discount visibility. The card networks with the strongest PADD 3 and PADD 2 coverage tend to deliver the largest absolute savings because the discounts compound on already-cheap base prices. If most of your miles are West Coast, prioritize cards with strong CA/OR/WA in-network presence — the discount is more valuable in absolute terms.

Compare fuel cards by route footprint — the right card is the one with the most stations on your lanes, not the largest network in raw count.

Bottom line

The spread isn't going away. CARB and state tax structures, refining concentration, and pipeline geography are decade-scale fixed. Plan around it: fuel where it's cheap when you can, run a card with strong coverage on your lanes, and remember that a $1.53 PADD spread is bigger than most spot-rate moves you'll see all year.

For weekly tracking of how the spread changes, see the diesel prices hub. For more on protecting margin in a soft market, see our freight rates coverage.