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?
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/
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.
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!
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
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”
deleted by creator
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.
AI is decent for writing, but a terrible choice for math.
ok but I am objectively a worse choice for math
Yes. 88 Octaine is 15% ethonol instead of 10%.
Isn’t summer fuel E0?
If anything, it would make sense to have gasoline with ethanol content in summer because ethanol is more knock-restistant, which you are more prone to if tempereatures are warmer.
Knock resistance is related to octane and not ethanol content directly I thought
You are correct. Ethanol does have a higher octane rating though so a blend of gas and ethanol will have a higher octane rating and hence knock resistance.
Ethanol usage in the summer creates smog and other pollution which is why it’s normally only for winter usage. Except this year, they allowed it to be used longer in an attempt to give Biden a boost in the polls
I googled a bit and the web said that ethanol does indeed burn cleaner which makes sense since there should be less contaminants and more oxygen is available. Ethanol also absorbs more heat then vapourized so there should be less heat in the combustion chamber resulting in less NOx emmissions. Do you have any sources for your claims? I would like to read about it because clearly i don‘t know everything about burning ethanol.
“Adding ethanol to gasoline is known to increase smog pollution in hot weather, but research has shown little difference between E15 and the more-widely available E10 blends.”
https://grist.org/energy/midwest-sell-ethanol-summer-smog-risk/
https://www.theverge.com/2022/4/12/23021146/biden-administration-ethanol-e15-gas-prices
This is the reason why it’s typically banned during summer months.
summer fuel?
There’s a difference between summer and winter fuel for gasoline engines in some areas. It’s usually to do with smog restrictions.
The same octane can be reached with different blends of hydrocarbons. So instead of just ‘pure’ gasoline to hit a desired octane, refineries can mix together higher and lower octane fuels to reach the same overall octane rating. This increases the amount of refinery products that can be used to blend gasoline, so it can be made more cheaply. The trade off is that it’s less pure, and most importantly for this comment - that some components of of these cheaper blends may evaporate more readily, leading to smog.
In summer, when it’s warmer, some areas mandate gasoline must meet certain standards for evaporation. In winter, those standards are decreased, because it’s cooler.
Ethanol has a relatively low evaporation point. I don’t know the specifics of the commenter’s location, but I could see ‘summer gas’ having no ethanol to meet these standards.
More info: The Vapor Rub: Summer versus Winter Gasoline Explained — Car and Driver
that’s wild. is this relatively new? I used to live in the Great White North and I’ve only been down in Florida for 10 years
I must confess - aside from knowing there was a difference, I didn’t really know what the difference was until a few online searches yesterday.
The understanding I have is that winter/summer gas programs began in the late 1980’s.
My supposition is that they have been handled seamlessly to the point that unless you are involved in regulation or the industry, it’s relatively inconsequential to most folks. I imagine knowledge of the program’s existence is probably one of those things that people sorta ignore unless it randomly becomes a topic of conversation. (Like any number of random regulations that impact our daily lives that we just don’t think about most of the time.)I did always wonder how they made up for the changing energy density due to temperature
I am not sure but I suppose it’s the opposite of what we have here commonly called winter fuel, which I think has some additives to help engines run better in low temperature conditions.
Are you thinking of diesel? Winter diesel has additives to stop it thickening in the cold weather
Yes
Octane is a measure of how prone to knocking the fuel is, not energy.
Knocking is premature combustion, I.e. why lead used to be added.
holy fuck you’re right. I always knew that higher quality fuels reduced knocking, but I thought it was a side effect of the fuel being more pure or something. I haven’t really put any thought into this since I was a kid
