A few corrections. Credentials: I am a Chemical Engineer in a Senior Tecnical Leadership position at a refinery with over thirty years of experience.

1) API gravity is the density of the crude oil. Higher API = lower density. We use this unit of measure because it magnifies the differences in densities vs. using conventional units of measure.

2) Refiners in the US mix different crude types to maximize the objective function ($) of a set of constraints including crude grade pricing and availability, product demand volume and pricing, refinery unit constraints and product quality specifications. This is done using a linear program model.

3) light and heavy crude contain the same molecules but in different ratios. For example they all contain gasoline, jet fuel, diesel boiling range material and all contain some amount of material that could be turned into ship fuel or asphalt for paving roads. Heavy crude tends to sell at a discount to light crude because of the laws of supply and demand - refiners will buy a mix of whatever makes them the most money.

4) “Most refineries in the US are very old and are very polluting”While US refineries sites are old - some site have been in operation for over 100 year, the units and configuration of the refineries has evolved continuously over the years. The technology used in the refining units has evolved as well - this is not a static industry. The pollution standard for refinery operations and fuel emissions have been raised multiple times. So “Very Polluting” vs. new refineries does not pass muster. US refineries have been retrofitting wet gas scrubbers and selective catalytic reduction units to reduce emissions of SOx and NOx for decades. These technologies reduce emissions of both pollutants by over 90%. Most of the emissions come from burning the fuel that refineries produce and both legacy US refineries and new ones have to meet the same fuel quality specifications and hence produce equivalent emissions.

5. “There are different blends of gasoline that the US produces. The biggest is so-called summer and winter blends. What's the differene? Additives are added to summer blends (in particular) to increase the boiling point so less of the gasoline is in gas form because that produces more smog;”

Summer gasoline contains less butane than winter gasoline. That is the main difference. Butane is added to winter gasoline so cars start in cold weather. There are no additives added to raise the boiling point in summer - just less volatile light material added.

As an aside, Mvodern gasoline vehicles have carbon canisters to capture vapors (such as butane) from the gas tank when not in service. These are then regenerated by sweeping air through them when the vehicles are running.

6. “ California uses their own blends so in 2021-2022 when CA gas went to $8+, it wasn't just "gouging". It doesn't really work that way. CA requires a particular blend that only CA refineries produce so it's simple supply and demand as no new capacity gets added to CA refineries and demand goes up with population growth. The reason for the CA blend goes back to the 80s and 90s when smog was a much bigger problem. Better vehicle emissions standards since then as well as improvements in the blends the rest of the country uses have largely made the CA blend obsolete so CA is really paying $1+/gallon more for literally no reason;”

There is some out of date information here. California is a net importer of gasoline since refinery closures in California have outpaced reduced demand from increased fleet fuel efficiency / BEV adoption. There are refineries in Asia that export California and some other US refineries can also make California grade gasoline but this requires shipping via the Panama Canal on Jones act ships that are scarce and expensive.

P66 / Kinder Morgan are planning a pipeline / pipeline reversal that would bring refined product into California including California gasoline.