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why do a bunch of gas stations have 88 octane cheaper than 87? (lemm.ee)

submitted 4 months ago by [email protected] to c/[email protected]

42 comments fedilink hide all child comments

I figured it was a marketing gimmick to get you to buy 88 and then they would finally raise the price, but it's been years. are they adding extra ethanol or something?

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[–] [email protected] 32 points 4 months ago* (last edited 4 months ago) (1 children)

E10 has an energy density of 108,608 BTU/gal and E15 has an energy density of 106,814 BTU/gal.

source: http://www.airimprovement.com/reports/national-e15-analysis-final.pdf

This gives us tha the 88 octane has 106.8/108.6 ≈ 0.983 times the energy density of the 87.

1-0.983 = 0.017

The correct number is that the 88 needs to be 1.7% cheaper than 87 to give equivalent distance per dollar.

LLMs are fantastic tech, good at many things. Math is not one of those things.