87 or 89 Gas which do you use?

[MF2020]

87 for me. Used it in my 2011 5.7 and using in my 2020 5.7 with etorque. I notice no difference between 89 & 87 in either power or milage, with or without a trailer seems to make no difference either.

 

[HSKR R/T]

That would theoretically be true; however, at least one member ran a test at all grades and observed the computer was still pulling timing (slightly) even on 93. So…maybe the HEMI tune leaves some room for additional performance.

Deoends the reason the PCM was pulling timing. It is written into the tune to pull timing during WOT shifts to be easier on transmission. So if you are reading log files and see timing being pulled at top of RPM right before shifts, that's why. There are a wide variety of reasons for timing to be pulled. Need to log more than just timing to reallying see what is going on. What is the LTFT and STFT? Oil temp, water temp, IAT reading..............

 

[SpeedyV]

Deoends the reason the PCM was pulling timing. It is written into the tune to pull timing during WOT shifts to be easier on transmission. So if you are reading log files and see timing being pulled at top of RPM right before shifts, that's why. There are a wide variety of reasons for timing to be pulled. Need to log more than just timing to reallying see what is going on. What is the LTFT and STFT? Oil temp, water temp, IAT reading..............

Understood, and valid points. I can’t speak for the member that shared this, but if all else were equal…

 

[BowDown]

Will create more deposits in cylinder, doesn't offer any advantage over 89 that the truck is tuned for.

Why would 93 leave more deposits vs 89 or 87?

 

[theblet]

 

[HSKR R/T]

Why would 93 leave more deposits vs 89 or 87?

SaMe reasom you will detonate on 87 but not 89

 

[Kaderast]

Am I the only person putting 85 in my Hemi?

 

[BowDown]

SaMe reasom you will detonate on 87 but not 89

That's an octane difference, and that will not cause deposits.
An octane difference has nothing to do with deposits being left, that crap gas or oil coming into the intake

 

[BowDown]

That would theoretically be true; however, at least one member ran a test at all grades and observed the computer was still pulling timing (slightly) even on 93. So…maybe the HEMI tune leaves some room for additional performance.

Too many other things could be causing that and the most simple and obvious is oil in the intake and intake runners. This will lower the octane rating on any fuel and potentially cause denotation

 

[Scram1500]

Thank goodness for catch cans

 

[Andymax]

Not true.
87 only allows for X ignition advance which is what creates low speed torque and upper room horse power.
Lowering the ignition advance decreases torque output requiring more throttle, more rpm and more fuel to accelerate to a specific speed.

We may only be talking 20-30 lbs ft of torque but over the course of a tank of fuel you'll consume more.
My previous truck averaged about 1.5 mpg less on the highway alone and I've seen the timing impacts on Dyno in my car

What did I say that is not true? Since the ECU compensates, as it's designed to do, timing for octane I get no ignition-related issues (knock/ping). I easily, and regularly achieve over 21MPG with my cruise set at 72, and over 20 set at 75. (BTW-this still blows my mind and makes me really happy). If I fill with midgrade fuel (89), I pay at minimum 10% more....there is no viable way to economically justify that as my mileage absolutely will not increase by 2mpg. I drive lots of highway, so any torque loss means relatively little unless I'm towing or hauling heavy. If that were the case then I might use 89, but that still would not compute to make economic sense.

 

[silver billet]

Deoends the reason the PCM was pulling timing. It is written into the tune to pull timing during WOT shifts to be easier on transmission. So if you are reading log files and see timing being pulled at top of RPM right before shifts, that's why. There are a wide variety of reasons for timing to be pulled. Need to log more than just timing to reallying see what is going on. What is the LTFT and STFT? Oil temp, water temp, IAT reading..............

I saw a video on youtube where a guy logged (hp tuners) his hemi with different gas. The point here is that the computer pulled much more timing on 87, than it did on 89. So while the "wide variety of reasons" may be true, those reasons would still be there when running on 87 vs 89 when that is the only difference between tests. What is being claimed is that these hemis so obviously run far better on 89+

 

[BowDown]

What did I say that is not true? Since the ECU compensates, as it's designed to do, timing for octane I get no ignition-related issues (knock/ping). I easily, and regularly achieve over 21MPG with my cruise set at 72, and over 20 set at 75. (BTW-this still blows my mind and makes me really happy). If I fill with midgrade fuel (89), I pay at minimum 10% more....there is no viable way to economically justify that as my mileage absolutely will not increase by 2mpg. I drive lots of highway, so any torque loss means relatively little unless I'm towing or hauling heavy. If that were the case then I might use 89, but that still would not compute to make economic sense.

That fuel economy is unchanged, that's not accurate.
Ignition advance = torque, period. Reduce the advance, reduce the torque output at a given rpm and you increase throttle input to obtain that same performance or rate of acceleration, that results in increased fuel consumption.

 

[BowDown]

I saw a video on youtube where a guy logged (hp tuners) his hemi with different gas. The point here is that the computer pulled much more timing on 87, than it did on 89. So while the "wide variety of reasons" may be true, those reasons would still be there when running on 87 vs 89 when that is the only difference between tests. What is being claimed is that these hemis so obviously run far better on 89+

Exactly, I don't see how theres an argument that 87 reduces performance

 

[GKIII]

That fuel economy is unchanged, that's not accurate.
Ignition advance = torque, period. Reduce the advance, reduce the torque output at a given rpm and you increase throttle input to obtain that same performance or rate of acceleration, that results in increased fuel consumption.

What you're saying doesn't make sense. The formula for horsepower is Torque x RPM / 5252. If you have a reduced torque output at given RPM you have reduced performance. Plus, it's not just the top end number you should be looking at, it's the area under the curve (as in gains made or lost along the RPM range).

Edit: Nevermind...I get what you're saying now. Fuel economy is affected by using more throttle (therefore increasing RPMs) to make the same power. Still finishing my first cup of coffee

 

[RAM Patriot]

Octane is simply the measure of detonation resistance. Detonation is a result of heating and compressing fuel and air until they auto ignite even before the spark plug is turned on.

A higher octane fuel can handle more heat and pressure before combusting.

Using a higher-octane fuel allows an engine to take advantage of an ideal timing curve without causing detonation. Once that timing has been achieved, there is no advantage to using higher-octane fuel.

 

[Andymax]

That fuel economy is unchanged, that's not accurate.
Ignition advance = torque, period. Reduce the advance, reduce the torque output at a given rpm and you increase throttle input to obtain that same performance or rate of acceleration, that results in increased fuel consumption.

And yet....so what??? I keep more money and my truck runs great. Period. I've driven an overall average of just over 30K miles per year since I started my career 33 year ago. My wallet math is far more significant, to me, in this case than your theoretical math. And I've tried 89 for several tanks in a row...my fuel economy difference is no where near even 1 mpg overall. 87 for me.

 

[BowDown]

And yet....so what??? I keep more money and my truck runs great. Period. I've driven an overall average of just over 30K miles per year since I started my career 33 year ago. My wallet math is far more significant, to me, in this case than your theoretical math. And I've tried 89 for several tanks in a row...my fuel economy difference is no where near even 1 mpg overall. 87 for me.

That's fine but say that instead of blanetley that it doesn't affect performance or fuel economy. As for mpg, do what you want, I can see an easy 1.5-2 mpg difference at highway speeds driving from Dallas to Houston as have many others

 

[Andymax]

This. Only difference is in the wallet. Manual clearly states 87 is fine. I drive 90% highway and regularly attain 20+mpg with no knock, no ping, no nuthin. Truck runs great.

That's fine but say that instead of blanetley that it doesn't affect performance or fuel economy. As for mpg, do what you want, I can see an easy 1.5-2 mpg difference at highway speeds driving from Dallas to Houston as have many others

You are splitting the finest of semantic hairs....to what end I really don't know. I was simply stating my experience and preference as the OP requested.

 

[Fuzznutz]

87 all day everyday. Can't even get anything higher at my home town station. They only recommend 89 cuz that's how they achieve those rigged fuel mileage numbers they print on the window sticker.

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