For the guys who think they get more power with 91 octane fuel

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I watched this video when it first came out ... I personally am not looking for more power from 91, what I am looking for is the denial of knock on our HEMIs which from how "MY" truck performs on 91 is much better than when I was using 89 the last year ... my MPGs have gone up by almost 2 mpg in town and the smooth acceleration is very noticeable especially when driving on the open highway ...

Just like I said in the octane thread, these engines are already built to make a certain amount of power "stock", unless you have modded the whole system then the 87-85 is going to give you more power vs the 91.

My opinion is that 91 has been marketed to a) get you to spend more money at the pump and b) get our vehicles to break down faster than the old engines without all the computer dependency ...

Most people today with the new cars will notice their vehicles running "better" with 91 especially since most sports cars are calling for 91 for optimal performance and the HEMI is no exception which is why I feel there are so many HEMIs with lifted and cam issues because people feel and decide to use 85, 87 and even 89 in these trucks ...

Regardless of which octane the normal HEMI owner uses, these engines will make the same power period but the risks of damaging the engine are much higher running 85-89 in my opinion .... so that is my reason for running 91 again in my truck, not for the power but for the prevention of damage down the road ...
 

Sillygoose

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I watched this video when it first came out ... I personally am not looking for more power from 91, what I am looking for is the denial of knock on our HEMIs which from how "MY" truck performs on 91 is much better than when I was using 89 the last year ... my MPGs have gone up by almost 2 mpg in town and the smooth acceleration is very noticeable especially when driving on the open highway ...

Just like I said in the octane thread, these engines are already built to make a certain amount of power "stock", unless you have modded the whole system then the 87-85 is going to give you more power vs the 91.

My opinion is that 91 has been marketed to a) get you to spend more money at the pump and b) get our vehicles to break down faster than the old engines without all the computer dependency ...

Most people today with the new cars will notice their vehicles running "better" with 91 especially since most sports cars are calling for 91 for optimal performance and the HEMI is no exception which is why I feel there are so many HEMIs with lifted and cam issues because people feel and decide to use 85, 87 and even 89 in these trucks ...

Regardless of which octane the normal HEMI owner uses, these engines will make the same power period but the risks of damaging the engine are much higher running 85-89 in my opinion .... so that is my reason for running 91 again in my truck, not for the power but for the prevention of damage down the road ...
You're on some stuff man....
 

Burla

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I can only say this, in my engine which the rumor is that it is tuned for 89, my truck sputters on 87 and runs like a ***** ape on 91, I am super cheap, if it ran good on 87 I would run 87, but the re-**** knock is noticeable to anyone in the truck. The only reason I use 91 instead of 89 is because costco only carries 91 and 87. When fuel is 7 bucks, I still run 87, but I miss my 91 on every trip. I must admit, I don't really know the science, I just know my eye sight can still tell the difference between night and day, and I can tell the difference between 87 and 91, and it isnt even close.
 
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You're on some stuff man....
You tell yourself that homie ...but it's a fact that my truck runs like a B@D@$$ on 91, again, not that it makes any more power, but it uses every bit of power it has the potential to use on 91. Using 89 will retard it and 87 will really make "Dumb & Dumber" ... but the stuff I am on is just too much for you
 
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I can only say this, in my engine which the rumor is that it is tuned for 89, my truck sputters on 87 and runs like a ***** ape on 91, I am super cheap, if it ran good on 87 I would run 87, but the re-**** knock is noticeable to anyone in the truck. The only reason I use 91 instead of 89 is because costco only carries 91 and 87. When fuel is 7 bucks, I still run 87, but I miss my 91 on every trip. I must admit, I don't really know the science, I just know my eye sight can still tell the difference between night and day, and I can tell the difference between 87 and 91, and it isnt even close.
Same here ... my truck is like like Scarlett Johansson in Lucy, the average HEMI on 89 and 87 uses 10% of it's brain capacity, with 91 it's like Lucy using 100% of it !!!
 
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I wonder what their results would be if they heat soaked the engine prior to the pull and had a computer control for knock...
Those tests are a little vague if you think about it, there are so many other factors that go and affect power ... while these tests are still good and cool to see, I don't really feel they are the tell all ...
 

HEMIMANN

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I can only say this, in my engine which the rumor is that it is tuned for 89, my truck sputters on 87 and runs like a ***** ape on 91, I am super cheap, if it ran good on 87 I would run 87, but the re-**** knock is noticeable to anyone in the truck. The only reason I use 91 instead of 89 is because costco only carries 91 and 87. When fuel is 7 bucks, I still run 87, but I miss my 91 on every trip. I must admit, I don't really know the science, I just know my eye sight can still tell the difference between night and day, and I can tell the difference between 87 and 91, and it isnt even close.

Thought you found an 89 to test against 91?
 

HEMIMANN

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@Wild one - still educating, eh?

I've returned to 89 octane after my brief foray into 87 during the great inflation hype.

Learning the PCM algorithm for spark timing advance made my decision for me. I didn't like the knock sensing setup. Yes, it does run better on 89, no sputtering, I've always noticed that. I just wasn't towing much this summer when gas was $5+ / gal for 87.
 

Burla

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Thought you found an 89 to test against 91?
not yet I will though, the issue is costco 91 is 40 cents cheaper then other stations 89 here, and since the latest crisis, that I wont do. But I do believe one of these days when I pass chevron the difference between the 2 will not be so large and then I'll try it.
 
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not yet I will though, the issue is costco 91 is 40 cents cheaper then other stations 89 here, and since the latest crisis, that I wont do. But I do believe one of these days when I pass chevron the difference between the 2 will not be so large and then I'll try it.
If you like your truck running like a r@ped@pe you are not going to like 89 ... I prefer my truck to run like a r@ped@pe myself lol ...
 

Docwagon1776

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Those tests are a little vague if you think about it, there are so many other factors that go and affect power ... while these tests are still good and cool to see, I don't really feel they are the tell all ...

Yup. What it tells you is what THAT motor under THOSE circumstances does.

Now, I don't think it's going to be a massive difference for most people under most uses. Granny driving to the grocery isn't going to note the difference in the way someone with a forced induction motor working hard up an incline on a hellishly hot day will.

I filled my PW with 89 when I bought it, since that's what I ran in my 1500. I now see the manual calls for 87 (yes, I'm actually RTFM...I have to in order to figure out all the things this new truck does...). I figure I'll run 89 for a couple tanks, repeat with 87, repeat with 93, track milage and 'feels' and then go from there. If I can get another 1-2 mpg to extend my range a bit I'll pay the extra.
 

dhay13

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There are a few variables to consider. Altitude, humidity, air temp, etc. Two identical engines may make different powers due to these variables. Heck, in my drag racing days if my engine ran great in the early morning it would run like crap in the heat of the day unless I adjusted the carb accordingly, like to the point of losing a couple of 10ths.
Like has been mentioned already, using a higher octane does not make more power, it lets you use the power that is available. If your engine combo is optimal on 87 octane then running 93 will do nothing for you. I built a 327 Chevy with 10.7:1 compression and cast iron heads but it would run fine on lower octane fuel as I had a roller camshaft with a low centerline and lots of overlap. My biggest issue was trying to get it to idle so I took bread tie wire and put it in the idle circuits and after that it would idle all day long.
 
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Wild one

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There are a few variables to consider. Altitude, humidity, air temp, etc. Two identical engines may make different powers due to these variables. Heck, in my drag racing days if my engine ran great in the early morning it would run like crap in the heat of the day unless I adjusted the carb accordingly, like to the point of losing a couple of 10ths.
Like has been mentioned already, using a higher octane does not make more power, it lets you use the power that is available. If your engine combo is optimal on 87 octane then running 93 will do nothing for you. I built a 327 Chevy with 10.7:1 compression and cast iron heads but it would run fine on lower octane fuel as I had a roller camshaft with a low centerline and lots of overlap. My biggest issue was trying to get it to idle so I took bread tie wire and put it in the idle circuits and after that it would idle all day long.
The good ole days of drilling holes in the throttle plates so you could keep the throttle blades closed enough,they weren't uncovering the transition circuits,lol. I built a couple low compression(9:1)/ huge camshaft combo's in my younger days,that were faster on 87 then they were on 91 or 93 at the track,but they needed a ***** pile of rpm and alot of convertor to work,but you could fill them up with 87 and drive both anywhere with-out over heating,like my high compression combo's would do
 

Rlaf75

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My 11 ram 5.7 ran fine on 87. It would pull my 7x11 enclosed trailer with 2 big Harleys in it through the mountains of upstate NY. My current 21 ram 5.7 runs fine with 87 as well. I don't beat on it. I drive it like the truck it is. My Harley on the other hand has 11-1 compression and tuned. It will not keep a piston in the jugs if I ran anything less than 93 octane. When I'm out of state I need to carry octane boost in case I can't get 93 lol.
 

mtofell

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I don't notice much, if any, difference going 87 to 89 octane but man when I get the non-ethanol my truck sure does run nice. I camp each summer at a remote place that only sells non-ethanol and it's nice. Sure, I can find it at home but it's usually $1-2 more per gallon so I'll pass.

Speaking of ethanol in gas I always remember what I read on one of these forums once.... A guy who had spent his life working in the fuel business as an engineer, etc. He knew a ton about fuel, refining and distribution. His opinion was that most vehicles get 10% less MPGs with 10% ethanol and the only reason it was mandated by our govt. in our gas was to keep corn farmers in business. I'm just the messenger but don't find it hard to believe that our govt. would do something that stupid.
 
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I don't notice much, if any, difference going 87 to 89 octane but man when I get the non-ethanol my truck sure does run nice. I camp each summer at a remote place that only sells non-ethanol and it's nice. Sure, I can find it at home but it's usually $1-2 more per gallon so I'll pass.

Speaking of ethanol in gas I always remember what I read on one of these forums once.... A guy who had spent his life working in the fuel business as an engineer, etc. He knew a ton about fuel, refining and distribution. His opinion was that most vehicles get 10% less MPGs with 10% ethanol and the only reason it was mandated by our govt. in our gas was to keep corn farmers in business. I'm just the messenger but don't find it hard to believe that our govt. would do something that stupid.
That is exactly why I run 91 on my truck ... it's non-ethanol gas here in California and my truck loves it ... when I tell you that I can feel the difference between 89 and 91 I mean it ... 89 and 87 have 10% ethanol and some very rare Chevrons don't have any ethanol in their 89 but very rare you find that gas station ...

So 91 from Chevron is what I will continue using on my truck ... hell, I even use it on my 1994 Toytota Corolla, that is all I have ever used on that car since I first bought it from my Father, he only used 91 from Shell or Chevron too and that is why it's still running after 340k miles lol ....
 
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