California summer blend gasoline is a low-volatility, low-emission fuel formulation that refiners must sell during the warm months to reduce smog. Its defining feature is a Reid Vapor Pressure (RVP) cap of 7.00 pounds per square inch, well below the 9.0 psi federal ceiling, and it phases in as early as April 1 in Southern California and the Central Valley.1Legal Information Institute. California Code Regulations Title 13 2262 – The California Reformulated Gasoline Phase 2 and Phase 3 Standards The California Air Resources Board (CARB) enforces the standard on a regional schedule tied to each area’s ozone risk.
What the Summer Blend Actually Is
Gasoline evaporates faster in heat, and those vapors react with sunlight to form ground-level ozone. RVP measures how readily fuel vaporizes at a given temperature, so lowering it directly cuts smog-forming emissions. California caps summer RVP at 7.00 psi for gasoline containing ethanol and 6.90 psi for non-oxygenated blends certified through the state’s Predictive Model.1Legal Information Institute. California Code Regulations Title 13 2262 – The California Reformulated Gasoline Phase 2 and Phase 3 Standards Refiners hit that target mainly by pulling butane and other highly volatile hydrocarbons out of the blend.
The summer RVP rule sits on top of California Reformulated Gasoline (CaRFG) Phase 3 composition limits that apply year-round: sulfur capped at 20 parts per million, benzene at 0.80 percent by volume, total aromatics at 22.0 percent, and olefins at 4.0 percent.1Legal Information Institute. California Code Regulations Title 13 2262 – The California Reformulated Gasoline Phase 2 and Phase 3 Standards Together these limits target both smog precursors and toxic air contaminants.
Lower volatility also helps drivers in hot weather. Gasoline with excessive vapor pressure can vaporize inside fuel lines before reaching the engine, a condition called vapor lock that causes stalling and hard restarts. Summer blend gasoline is much less prone to it.
When Summer Blend Starts and Ends in Your Region
California does not flip a single statewide switch. CARB divides the state into five RVP control categories by air basin, with hotter and more ozone-prone regions starting earlier and ending later.2California Air Resources Board. Reid Vapor Pressure Control Periods
- Category A, April 1 through October 31: the South Coast Air Basin (Los Angeles, Orange, Ventura, and western portions of San Bernardino and Riverside counties), San Diego, Mojave Desert, and Salton Sea air basins.
- Category B, May 1 through September 30: San Francisco Bay Area and Great Basin Valleys (Alpine, Inyo, and Mono counties).
- Category C, May 1 through October 31: San Joaquin Valley, Sacramento Valley, Mountain Counties, and Lake Tahoe air basins.
- Category D, June 1 through September 30: North Coast (Humboldt, Mendocino, Del Norte, Trinity counties), Lake County, and Northeast Plateau air basins.
- Category E, June 1 through October 31: North Central Coast (Monterey, Santa Cruz, San Benito counties) and South Central Coast except Ventura County.
The longest control period runs seven months and covers the most smog-prone parts of Southern California and the Central Valley. The shortest runs four months in the far north, where cooler temperatures make evaporative emissions less of a concern.
How This Compares to Federal Rules
Under the Clean Air Act, the federal RVP cap during the summer ozone season is 9.0 psi.3U.S. Environmental Protection Agency. Gasoline Reid Vapor Pressure Fuel blended with 10 percent ethanol gets a 1-psi waiver federally, raising the effective limit to 10.0 psi.4Office of the Law Revision Counsel. 42 USC 7545 – Regulation of Fuels California’s 7.00 psi cap is roughly 30 percent lower than the federal number even before the ethanol adjustment. The federal summer season runs June 1 through September 15 in most areas, while California’s Category A regions enforce their tougher limit from April 1 through October 31.
CARB’s authority to go beyond the federal baseline comes from the California Health and Safety Code, which directs the board to adopt rules necessary to carry out its air quality mission.5Justia Law. California Health and Safety Code 39600-39619.6
Why Gas Prices Rise in Spring
Drivers reliably see prices climb during the spring transition, and summer blend is one of the reasons. Removing butane and other cheap, high-volatility components makes summer gasoline more expensive to produce. Refineries also typically shut down individual processing units for maintenance in late winter and early spring to prepare for the switch, which cuts output right as demand for the costlier product ramps up. Because California’s control period starts before most other states, West Coast prices tend to rise before the rest of the country feels the seasonal pinch.
Summer blend is not the only California-specific cost driver. The state’s cap-and-trade program adds roughly 20 to 30 cents per gallon, and the Low Carbon Fuel Standard adds another 5 to 8 cents. Stacked on top of state and federal excise taxes, these programs help explain why California gasoline consistently costs more than the national average, with the gap widening during the summer blend season.
Emergency Waivers When Supply Is Disrupted
When a refinery fire, pipeline failure, or other supply shock hits, CARB can temporarily relax RVP requirements. This is not a formal waiver written into the regulations. CARB exercises enforcement discretion, typically at the Governor’s direction, to allow the early sale of winter-blend gasoline before the control period ends. In September 2023, the Governor directed CARB to permit an early transition to address what the agency described as “extreme fuel supply circumstances.”6California Air Resources Board. Early Transition to Winter-Blend Gasoline Advisory All other CaRFG requirements for sulfur, benzene, and other regulated properties stay in force during those windows.
At the federal level, EPA can grant emergency fuel waivers under the Clean Air Act, but they are capped at 20 days.7U.S. Environmental Protection Agency. EPA Fortifies Domestic Fuel Supply, Provides Americans With Relief at the Pump A federal waiver does not override California’s separate state fuel composition rules, so fuel sold in California during any relief window still has to meet the non-RVP portions of the CaRFG standards.
Penalties for Selling Non-Compliant Fuel
The Health and Safety Code treats intentional violations severely. A person who willfully and intentionally violates a fuel standard or CARB regulation faces a civil penalty of up to $250,000, plus an additional penalty equal to any economic benefit gained from selling the non-compliant fuel.8California Legislative Information. California Health and Safety Code 43027
Each day a violation occurs counts as a separate offense, so a refiner or distributor supplying off-spec fuel over a multi-week period can face enormous aggregate liability.9California Legislative Information. California Health and Safety Code 43030 Retail stations are not exempt. CARB conducts field inspections, sampling fuel directly from pumps, and if a sample fails, the delivery paper trail determines who in the supply chain answers for it.