Summer blend is here . Called local gasoline supplier and verified it .

https://www.eia.gov/todayinenergy/detail.php?id=11031

"For logistical reasons, the transition to low-RVP gasoline happens over the course of several spring months as temperatures rise and to facilitate lowering the RVP of remaining inventories of winter-grade gasoline. The federally mandated dates for summer-grade gasoline and reformulated gasoline, where required, are May 1 to September 15 for refiners and terminals, and June 1 to September 15 for gasoline retailers. In California switchover dates are earlier, and summer-grade gasoline must be in use for a longer period."
 
The transition started March 1st here, and in all likelyhood has been all summer fuel since April 1st or so...

The transition happens earlier than most folks think it does...
 
They may have leaned a little too far out on their ski's. It has snowed here every day for the last 5 days :poop:
 
Why is this a thing anymore? Nearly all cars are fuel injected with the fuel supply system under pressure starting from the tank. Gasoline volatility shouldn't be a factor anymore.

That being said, there are many classic car owners with carburated engine that experience vapor lock in the summer. I experienced this myself with my 71 Cutlass. So are they really lowering the gasoline vapor pressure during the summer?
 
That being said, there are many classic car owners with carburated engine that experience vapor lock in the summer. I experienced this myself with my 71 Cutlass. So are they really lowering the gasoline vapor pressure during the summer?

Actually the purpose of summer fuel is to reduce evaporating fuel getting into the atmosphere. Thus a lower Reid Vapor Pressure reduces the chance for vapor locking a carbureted fuel system.

They heat gasoline in a closed chamber to 100 degrees F and measure how much psi is in that closed chamber. Typical summer fuels will be in the 9 psi range and winter fuels are typically in the 14-15 psi range.
dismissing the whole ethanol thing, summer fuel since the 1990's is better for carbureted vehicles.
 
Noted it on my fill up for the Sportwagen from Costco a few days ago...logged it and noted less knock/timing correction so I'd say summer blends are here. Its very easy to see the difference in the summer vs. winter fuel logs in this car (tuned) just looking at a 3rd gear WOT pull to redline.
 
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