why do a bunch of gas stations have 88 octane cheaper than 87?
why do a bunch of gas stations have 88 octane cheaper than 87?
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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That cheaper 88 octane fuel is a blend of 85% unleaded gasoline and 15% ethanol. It's also known as E15 fuel.
The ethanol is an oxygenate: it adds oxygen atoms to the fuel mix so the fuel burns more completely. That's good for vehicle emissions. However, the ethanol is less energy dense than gasoline so you will get slightly worse mileage.
https://www.motortrend.com/news/what-is-e15-gasoline-pros-cons/
okay so I had AI do the math for me.
the 88 octane fuel with 15% ethanol would need to be approximately 4.7% cheaper than the 87 octane fuel with 10% ethanol to compensate for the lower fuel efficiency caused by the higher ethanol content.
okay so I had AI do the math for me.
"I drove a screw with a hammer"
cool story
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.
yeah that's why I labeled it as ai. like I can figure it out as a word problem to tell somebody, but I can't figure out the math from there
I didn't feed it the energy density of e10 vs. e15, I just told it that ethanol was 30% less efficient, and gave it the percentages.
The AI does nothing with the percentages because it is an LLM, not an AI designed for math. All an LLM does is take a small number of words and turn them into a different set of words. It does not use your small set of words to run any formulas on your behalf.
Years ago I had an E85 compatible vehicle when that was how we were going to save the planet before hybrids came along. E85 was cheaper than unleaded, but after crunching the numbers it was always the exact same cost per mile. Considering there were almost no stations with E85 fuel available, it just never made sense to go far out of my way to pay the same.
does it still eat away at your seals or have they fixed that
Both. Ethonal is still corrosive and the majority of fuel systems these days are compatible with E15. That said, check your owners manual.
Just finished restoring an old Jeep and had the brand new fuel pump give up within the first tank of regular gas. Everyone I talked to the first thing they asked was, "Did you use ethanol free gas?" Like it was some street smarts thing I should have known.
I would have thought by now any component built in the last decade would be built to withstand modern gasoline mixes. Joke's on me.
Depending where you live, it can be really hard to find ethonal free gas. As an added bonus, carburators hate having ethonal sit in them. They'll develop a varnish. Carbs also don't like sitting partially dry and getting all the fuel out of them is a massive pain. Yay lawn equipment.
My dad thought it was silly for me to replace my gas powered motor with an automatic throttle control that doesn't really work with an electric one, but having no knowledge or desire to rebuild a carburetor (like him), I think I made the right move.
My electric chainsaws and weed whacker always start. Eventually our lawn tractor will kick the bucket and I'll either convert it to electric or buy one.
They're so much quieter, too. Not as easy to notice when you're the one using the tool, but compare how it sounds to be nearby someone else using one and it's a biiiig difference
Problems with ethanol in gas usually happen over a longer time, not within a single tank of gas. That pump was probably faulty to begin with. I would recommend lower ethanol fuel for older vehicles though, so it's not bad advice. But it isn't like pure acid that will dissolve the car within no time.
Appreciate your perspective. Makes more logical sense than the "shouldn't have used ethanol" responses I got. Thanks!