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/
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.
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.
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.
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.
are they adding extra ethanol or something?
Yes. 88 has up to 15% ethanol. You should check your manual before using it.
Yes. 88 Octaine is 15% ethonol instead of 10%.
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
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
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
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.
