If you’ve filled up the tank in your car, SUV, or pickup in the past few days, you probably bought your first batch of winter-blend gasoline since the spring. It’s unlikely that you noticed a difference — only a refining geek with a nose for this sort of thing would — but winter gasoline has a higher Reid Vapor Pressure than summer gasoline, and therefore evaporates more quickly and emits more fumes. There’s a logic to EPA’s mandated switchover from lower-RVP gasoline to higher-RVP gasoline each September, and their switch back to lower-RVP each April/May. For one thing, using different gasoline blends during the colder and warmer months helps ensure that your engine runs well year-round; for another, reducing gasoline vapor pressure in the summer reduces emissions that contribute to smog. Today, we discuss gasoline RVP, why it matters, and how refineries ramp it up and down. (A hint is in the blog’s title.)
Tank Full of (Butane) – Summer Gasoline, Winter Gasoline, and Reid Vapor Pressure
