Switching to 87 octane?

[Dan98]

Did you try taking it back to the dealer while it's still under warranty? It shouldn't ping at all, it should retard the timing to prevent pinging so there's either something wrong with the knock sensor system or your local gas station is ripping you off with 70 octane gas. Sure it probably won't perform as well with 87 as with 89 octane but it shouldn't ping, especially not horribly as you said

He is probably running to much ethanol that will cause ping under load. Yes I know ethanol has over 100 octane rating but its alcohol not petroleum.

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[canadiankodiak700]

He is probably running to much ethanol that will cause ping under load. Yes I know ethanol has over 100 octane rating but its alcohol not petroleum.

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More ethonol would reduce ping as it has more octane.
Octane is octane doesn't matter if it's petroleum or ethanol
octane is a measurement

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[kurek]

If you want to get super nerdy, octane is a specific petroleum molecule that is found in gasoline. Gasoline is a range of several molecules and octane is the one that has 8 carbon atoms.

But also octane is a relative measurement that we use when burning fuels in combustion engines and ethanol has a higher relative octane than pretty much any of the usual molecules that are in gasoline. Another reason ethanol won't cause ping under load is that ethanol contains oxygen and since that oxygen participates in the combustion process it gets into the cylinder without passing through the throttle body and without bringing along all that inert nitrogen. This means that for a given mass of hydrocarbons being combusted there is less nitrogen taking up space in the cylinder and because of that your effective compression ratio is lower at any given power output.

 

[ShortRAM]

Actually, octane is a BAD thing. Refineries maintain a laboratory to test their products. The lab has a small gasoline engine, called a knock engine. The gasoline being tested is used to run the engine. The lab technician slowly introduces octane into the mixture until the engine starts to knock. The better the gasoline, the more octane it can have in the mixture without knocking.

 

[Dan98]

Ok so would ethanol burn at the same rate as 93 octane non ethanol??
Maybe that's a dumb question

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[kurek]

That's going to depend on what you mean by rate.. the flame front speed is similar though ethanol burns at a more uniform rate and more quickly per ignition ( https://core.ac.uk/download/pdf/77014245.pdf ) . If you mean the rate of consumption, ethanol will be consumed faster because a portion of it is oxygen that you are buying in the fuel molecules. With pure petroleum all of your oxygen comes in through the air filter (financially) for free.

 

[HEMIMANN]

Cool! Post evolving into combustion dynamics thread!

Still don't miss thermodynamics, though. Yeah, technically octane describes C8H18 hydrocarbon, but the R+M/2 rating is the API standard for resistance to detonation.

Goes back to Av Gas high octane for max power recip WWII aircraft, but higher octane can also leave deposits due to the longer chain molecules being combusted (& or cyclic hydrocarbons).

The key is, unless your engine has an integrated knock sensor and ignition timing closed loop control, do not put in higher octane fuels than recommended. You will not only waste money, but leave more deposits.

 

[canadiankodiak700]

Actually, octane is a BAD thing. Refineries maintain a laboratory to test their products. The lab has a small gasoline engine, called a knock engine. The gasoline being tested is used to run the engine. The lab technician slowly introduces octane into the mixture until the engine starts to knock. The better the gasoline, the more octane it can have in the mixture without knocking.

You are getting your info mixed up

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[Nova John]

I have a 2011 Ram with 392 gear 87 performance tune flowmaster exhaust and K&N drop in. I use 87 octane and it runs fine. If I use 93 with 87 tune it runs better and faster quarter mile time. 93 tune with 93 octane didn't run much better than 93 with 87 tune. Had slight pinging with 93 tune and 93 octane so went with 87 tune. Usually alternate 87 one tank and 93 next tank. Ran non ethanol a couple years ago while on vacation in the mid west. Got 24.5 mpg. 3 miles a gallon better than with ethanol blend. Too bad can't get non ethanol in NJ.

 

[rule18]

I have a 2011 Ram with 392 gear 87 performance tune flowmaster exhaust and K&N drop in. I use 87 octane and it runs fine. If I use 93 with 87 tune it runs better and faster quarter mile time. 93 tune with 93 octane didn't run much better than 93 with 87 tune. Had slight pinging with 93 tune and 93 octane so went with 87 tune. Usually alternate 87 one tank and 93 next tank. Ran non ethanol a couple years ago while on vacation in the mid west. Got 24.5 mpg. 3 miles a gallon better than with ethanol blend. Too bad can't get non ethanol in NJ.

You can, it might not be so convenient to go to Fort Lee. https://www.pure-gas.org/index.jsp?stateprov=NJ

 

[ShortRAM]

You are getting your info mixed up

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You are correct. It is actually the compression that is increased to cause the knock. Thanks for the good catch. It has been over 30 years since I worked in the refinery and sometimes I am grateful to remember my own name.

 

[noodles]

You can, it might not be so convenient to go to Fort Lee. https://www.pure-gas.org/index.jsp?stateprov=NJ

Stewart's in NY has non-ethanol on some of the grades.

 

[rule18]

Stewart's in NY has non-ethanol on some of the grades.

Yep, I go frequently. I'm not sure that Nova John is close enough to NY to make it worth the trip.

 

[Nova John]

I have bought gas at Stewarts when I go to Lake George. Got 20 mpg towing boat home a few years ago. Saw the one in Fort Lee but think that is avaiation fuel and don't think you can use that with catalatic converter. If it's 92 or 93 octane I will make the trip as I could use it in snowblower riding motor and boat motors and truck.

 

[rule18]

I have bought gas at Stewarts when I go to Lake George. Got 20 mpg towing boat home a few years ago. Saw the one in Fort Lee but think that is avaiation fuel and don't think you can use that with catalatic converter. If it's 92 or 93 octane I will make the trip as I could use it in snowblower riding motor and boat motors and truck.

Weird, I thought the Fort Lee was a Sunoco but maybe they restrict sales to cans rather than directly into a truck?

 

[Nova John]

Fort Lee is a Sunoco but has 98 and 100 octane gas. Might be cam 2 racing gas with lead or airplane gas, not sure. I called and left a message so should hind out. There is also a station on rt33 in Milltown that has 95 octane. Most non ethanol gas is between 89 and 92 octane that they sell in NY and PA.

 

[Dan98]

If you want to get super nerdy, octane is a specific petroleum molecule that is found in gasoline. Gasoline is a range of several molecules and octane is the one that has 8 carbon atoms.

But also octane is a relative measurement that we use when burning fuels in combustion engines and ethanol has a higher relative octane than pretty much any of the usual molecules that are in gasoline. Another reason ethanol won't cause ping under load is that ethanol contains oxygen and since that oxygen participates in the combustion process it gets into the cylinder without passing through the throttle body and without bringing along all that inert nitrogen. This means that for a given mass of hydrocarbons being combusted there is less nitrogen taking up space in the cylinder and because of that your effective compression ratio is lower at any given power output.

You are so wrong about ethanol it absolutely causes pinging good god listen to your self tell me if you believe yourself. Or acutely research it wtf

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[kurek]

The nice thing about chemistry and physics is that they work the same regardless of anybody's opinions.

 

[boblonben]

Alrighty so Im closing on a house tomorrow. My truck currently is tuned to 93 octane. I have a 87 octane tune aswell (both from Jay). I want to save some money / don't exactly know the new area too well and not every station has 93 octane.

So want to ask you guys. No one possibly sees an issue with me detuning my truck to 87 and running that for a few months while I get to know the area better? Engine is stock other than a air intake.

I don't see an issue with it. Manual states 89. But research shows A LOT of people run 87. I've never put 87 in.

 

[boblonben]

You are so wrong about ethanol it absolutely causes pinging good god listen to your self tell me if you believe yourself. Or acutely research it wtf

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Ran non-ethanol in my 2020 5.7 for a straight 6 months, 87 octane AND 91 octane. Found no difference between them, and actually slightly better mileage over ethanol gas previously used. Could ell no difference in everyday performance. Did run it on a dyno found here was a 10hp difference, oh well. Now back o ethanol gas as I moved and non-ethanol is harder to find here.