90 octane Ethanol free gas or 93 octane 10% ethanol...

[-RAC-]

Which would you run? Just wondering what your thoughts are.

I have a buddy who has a large car collection and everything he drives uses the ethanol free, even his exotics and new cars. He swears by it. Is there any real benefit other then not having the rubber hose eaten up by the ethanol?

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[K4fxd]

When I lived in Louisiana I was able to get 93 octane pure gas. My car loved it. I got 5 more MPG and the butt dyno said it made more power.

Now with the loss of 3 octane points I believe the power level would be the same and the gas mileage would increase using the straight gas.

 

[FreePenguin]

higher octane. 93 is still better than 90 pure.

 

[K4fxd]

higher octane. 93 is still better than 90 pure.

I would have to test it but I think the power numbers would be equal. ( I know the MPG will be better) Try some pure gas the oxygenating effects do not come into play at 10 %

 

[FreePenguin]

I don't know if it really works that way, for mpg yeah as there's more energy in it I think its called, but 93 octane is still higher than 90 octane even if its pure fuel. 93 resist detonation more than 90.

reason I think this, is I have 91 ethanol free down road from me, or used to I think they got rid of it. no one was really wanting to pay the additional 20c a gallon when 93 with up to like 12% ethanol was 20c cheaper and had higher combustion.

I had a big thread about it along while ago and the tuners said use 93, it provides the most power for HP, but yeah, mpg you could see more mpg on the pure gas. but for timing/all that jazz. if you want the most power/tq even though has ethanol, its still 93 > 90.

would love to read arguments to me being wrong though. but thats what everyone told me. I think ethanol burns a bit cooler too though, adds a little cooling to the cylinder.


so if you are driving, not romping on it. 90 would be ok. but if you are WOT and playing spirited, you want the highest octane you can get. shoot for 93, even though has ethanol

so if your car calls for 91 recommended, I would pick 93 w ethanol all day, over 90 pure gas. you will not get as good as MPG with ethanol, but its still higher octane in the end.is there really anything wrong with ethanol? other than letting it sit over winter? toss some stabilizer in it lol

 

[Groovy]

I had only run Shell 93 until one day I tried ethanol free 92 gas. My tank was almost empty when I filled up. As soon as I left the station the engine started to sputter and pop. Freaked me out. It did clear up. So, tried a 2nd tank from another location. The car just didn't seem to rev as quickly as before. So, I went back to Shell 93. Fortunately my rev happy 2019 5.0 came back just as strong as before. So, I'm going to guess the ECU had to pull a bunch of timing out when using the ethanol free gas. Now in years past I've purchased ethanol free gas in my F150 and the mileage went up dramatically. Performance was unchanged. I don't think I'm going to try this again in my mustang. The only think I might try is a tune for E85 as there is a pump a couple of miles from home.

 

[-RAC-]

I had only run Shell 93 until one day I tried ethanol free 92 gas. My tank was almost empty when I filled up. As soon as I left the station the engine started to sputter and pop. Freaked me out. It did clear up. So, tried a 2nd tank from another location. The car just didn't seem to rev as quickly as before. So, I went back to Shell 93. Fortunately my rev happy 2019 5.0 came back just as strong as before. So, I'm going to guess the ECU had to pull a bunch of timing out when using the ethanol free gas. Now in years past I've purchased ethanol free gas in my F150 and the mileage went up dramatically. Performance was unchanged. I don't think I'm going to try this again in my mustang. The only think I might try is a tune for E85 as there is a pump a couple of miles from home.

Good to know. I thought about trying the ethanol free but gave pause when the manual said nothing below 91 or void warranty. My buddy runs his 2019 ZR1 on the 90 ethanol free with no noticeable loss of performance or he does not drive it hard enough.

 

[armykyle1 [HACKED ACCOUNT]

I would only suggest ethonal free if the vehicle sits for long periods. But 93 with ethonal blend will yield more power.

 

[drummerboy]

For what it's worth (and some may call me crazy), I'm absolutely 100% convinced the computer is very aggressively adding and pulling timing right on the bleeding edge of what the fuel can deliver. Here is my experience:

My first fill up at 2 miles on the odometer was with 91 premium here in CA. On that first tank, I heard it knock a few times leaving the highway, heading uphill on exit ramps at lower RPM (well, relatively lower anyway, given the Voodoo). Give it a slight bit of throttle, perhaps engine ever so slightly lugged, and for the tiniest fraction of a second I hear a couple knocks. And I mean that literally, no way to know for sure, but I'd hear just the quickest couple of ticks you've ever heard if you're listening for knock. Which I wasn't, but I noticed it.

Luckily for me I have a gas station that has CA legal 100 octane close by, so I went there for the next fillup and splashed it with that to take it to 95ish. I made a habit of that and never thought twice about it til once I had to fill up with 91 again. And guess what I heard again while not even listening or paying attention... the quickest/most brief T T in exactly the type of circumstance you'd expect to hear a knock.

For me that confirmed it - the computer is absolutely trying to push the timing as far as possible, beyond what 91 is capable of delivering. So I always put the 100 in at least 1/3 of the tank so that it is impossible to be at less than 94 and then do the math afterwards. I always land between 94.5 and 95.5

Lastly, I read on here somewhere that the dynoed difference between 87 and 93 on the Voodoo was 15hp. I have no idea about the veracity of this claim, but I 100% believe it.

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