I know 93 octane post. But, hear me out.

I've experienced some hesitation across the lower end of the rpm band when accelerating every so often. I'm just over 1300 miles now. I'll try the premium grade next fill up to see if there's any difference. I thought nothing of it really until reading this thread... had chalked it up to the crappy drive by wire lag but now I wonder. I don't hear any knocking or anything like that. It just feels rough climbing up the rpm range intermittently.

 

Try it. If it helps, great!

 

Kinda hard to not notice the rumble strips feel that comes with low octane fuel in my truck at cruising rpms. Your truck may be different, hopefully it is. My truck runs like absolute dog shit on 87. Period. 93 fixes all of it. 24k miles of usage is plenty scientific to me. Plenty of people have data logged their trucks and proven this.
Higher octane has nothing to do with more power or better mileage, it has everything to do with the truck not feeling like shit.

 

I know what my but dyno tells me. I know how much difference engine sounds. I'm not saying it is night day. But, I have been tuning engines in vehicles for 30 years. I know when there is a little difference. I see some others agree. That's enough for me. It be really interesting to do a test with 87 and 93 and see what happens. But, there so many other factors involved.

 

For those who swear by an increase in MPG increase using higher octane, keep in mind that some stations also lower the ethanol percentage as you buy their higher grade (incentive to buy), thus more boom boom per dollar.

 

No stations lower the ethanol content.

At some stations you can buy ethanol-free gasoline, but the gasoline either has ethanol or it doesn't.

 

What is the reason ethanol free is highly sought after? I want to be educated a little about this as I see it being mentioned from time to time, and googling it doesn’t explain much other than mpg being better? Is it cleaner?thanks in advance!

 

I've read that ethanol free gas will yield better MPG, but I think the main reason it's available in some places is that some older engines don't take kindly to ethanol blends. I'm by the water and it seems like boaters love ethanol free.

I use ethanol free in my lawn mower and motorcycle because I've always been told exhaust temps are lower using ethanol free. In cars, I'm sitting in AC so I'm good with the E10 stuff.

Edit - found this article explaining it in detail.
https://extension.psu.edu/fuel-ethanol-hero-or-villain

 

I never had better mileage with higher octane. Not even in my turbo car. But civic sport claims more power with premium fuel.

 

Phase separation. It occurs when enough water contaminates gasoline, causing ethanol to attach itself to water molecules, leaving two distinct layers in the storage tank, a gasoline-only layer at the top and an ethanol/water "cocktail" along the bottom.

This ethanol/water "cocktail" is problematic but not usually catastrophic when consumed.

So this is why ethanol free is very common in boats or things that sit for a long time. Water contamination is far more likely in both cases.

For a modern car that goes through a tank of gas every couple of weeks this is basically a non-issue. Water contamination will be minuscule and thus you shouldn't have any problems. That being said...phase separation can occur before the gas ever gets to the gas station. A member on here who claimed to be in the business posted that this happens quite frequently. This could result in you getting a good bit of the cocktail that's at the bottom of the gas stations tanks or you could get low octane fuel from a tank that had experienced phase separation. Ethanol has a high octane rating (113 RON) and that is factored into the octane rating of E10 (10% ethanol, 90% gas). So if you took the ethanol out of E10 87 (which is exactly what phase separation will do) you would be left with something in the mid to low 80s.

Ethanol free takes all of this out of the equation. It's pure gas.

 

Ahhh thank you for this!

Maybe this is what I've been experiencing? I should throw in a bottle of HEET at my next fill up instead of the splurging on premium. I read your post and the lights in my head flickered. It all sounded so familiar and then I remembered I used to do this every winter back in my college days with my old clunker. Seemed like a lifetime ago. My memory is definitely not what it used to be.

 

Nicely put, and since ethanol is hygroscopic it will pull water from the air itself.

 

So this essentially answers your question, @jayrobot. EtOH is added to gasoline as an oxygenate to reduce emission particulate and increase the octane rating of gasoline. EtOH is as a replacement for MTBE, which in turn was the replacement for tetraethyllead. Unfortunately, MTBE is extremely soluable in water and is carcinogenic, hence it's phase-out in favor for EtOH.

Keeping in mind the specific gravity of pure water is 1.00, the specific gravity of gasoline is ~0.74, meaning that gasoline will "float" on water. Ethanol has a specific gravity of ~0.79. So if you were to layer the three liquids atop one another like a cake, gasoline would be on top, ethanol in the middle, and water on the bottom. So, as ethanol is hydroscopic and will absorb water from the atmosphere in addition to free water, two things can happen:

1. Excessive volume of water can lead to the phase separation that @Doggman discussed above and a whole slew other problems, or

2. A small volume of water that has been absorbed by the ethanol will form a gum which will foul sensitive electronics, hoses, mechanical parts, etc. Gums form rather quickly in very very low amounts, is something gasoline additives are meant to address. Also, the idea is that gasoline will be consumed rather quickly, thus preventing these reports scenarios from being a problem of consequence. Leave the gasoline sit and problems will arise.

One more note regarding the phase separation of gasoline: it doesn't have to have ethanol to stratify. Gasoline is a heterogeneous solution of several different components of varying molecular weight and composition. Let the gasoline sit for long enough, or don't refine or blend it properly, and the components will more or less fall out of solution.

So to summarize: non-EtOH gasoline does not have the issues caused exclusively by ethanol. The refiner uses more high-quality and expensive components to blend the required grade of gasoline. Ethanol-free gasoline is a more dense fuel in terms of energy per pound than E10, so that's a small benefit as well. However, as the cost to produce the ethanol-free gasoline increases, so does the cost to the consumer. Ethanol is an "economically" viable alternative that, while having a massively powerful and influential lobby in Washington DC, has legitimate benefits.

 

Ultimately, there are solid and legitimate arguments for and against the use of ethanol. I personally don't care; none of my vehicles sit long enough to have issues with gasoline, and it's not rational for me to drive a hour to refuel with non-ethanol gasoline.

 

Ethanol has less energy density than gasoline does.....thus less boom per liter........so more fuel is required to make a commensurate amount of power.

 

I put in a bottle of HEET (red one) and so far so good. Smooth acceleration all throughout the rev range.

Maybe I had some bad gas from not driving much (only 1400 miles in 3 months) and the truck just sitting in the garage in this hot and humid weather here in south FL?