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Better MPG with higher octane?

mmondich

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2021 Ram 1500 5.7HEMI eTorque. Has anyone has run 87 octane and noticed a significant change when switching to a higher octane? I know the manual says no lower than 89 but other than MPG potentially being impacted, I don't have any issues. Would possibly spend the extra $$ if I knew it would yield higher MPG's. Thanks.
 

Mountain Whiskey

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No nonsense. Just seems I understand how the PCM works better than you. It never "advances" timing beyond the factory tune, and will only advance timing if LTKNK was reatrding timing due to knock sues.

And, as I said, the only reason the manul says you can run 87, is because the knock sensors are there to retard timing if they see see knock. Just because it doesn't spell it out in black and white, for people like you, doesn't mean that's not how it works.

I dont have a lemon, just care for my truck. And I've already saidI run 91 non-ethanol because I have the Edge Pulsar installed on my truck which requires 91+ fuel.
I see whoever typed the manual typed too fast for you also. It does not say "can" nor does it imply that this is at the detriment of your engine. It says the Hencho en Mexico motor was designed to run on 87.

I would not really think the unlocked pcm tweaking the broad stroke design limits of the factory is caring for the truck. Unless you install this just to baby it and claim it is there.

Good luck.
 

HSKR R/T

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I see whoever typed the manual typed too fast for you also. It does not say "can" nor does it imply that this is at the detriment of your engine. It says the Hencho en Mexico motor was designed to run on 87.

I would not really think the unlocked pcm tweaking the broad stroke design limits of the factory is caring for the truck. Unless you install this just to baby it and claim it is there.

Good luck.
I'm done. Tried my best to explain. You have zero comprehension about how the PCM works. The manual also does not say the truck is "designed to run in 87" and literally says 89 is recommended for best performance. Which anyone with common sense would realize that is what it actually "designed" to use. Anything else is a compromise.

As for the Pulsar, once again, you have proven you have no clue what you are talking about. Have a good evening. You do you with your truck, and I will do me.
 

CanRebel

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No nonsense. Just seems I understand how the PCM works better than you. It never "advances" timing beyond the factory tune, and will only advance timing if LTKNK was reatrding timing due to knock issues.

And, as I said, the only reason the manual says you can run 87, is because the knock sensors are there to retard timing if they see see knock. Just because it doesn't spell it out in black and white, for people like you, doesn't mean that's not how it works.

I dont have a lemon, just care for my truck. And I've already said I run 91 non-ethanol because I have the Edge Pulsar installed on my truck which requires 91+ fuel.

You are dead wrong....

These trucks are tuned for 87... Go ask Ram. Or better yet bring it Dyno Shop with a tuner...
Tune the Truck for higher Octane, you will really notice a difference....

The reason the manual says 87 is ok, cause it's tuned for it. it says 'recommended' on purpose. It's marketing. Ram isn't only company that uses that term...
If it said "required" and you put 87, you would/could cause issues.

The computer and injection system is always monitoring detonation, fuel, and air. Then adjusts.

A lot depends on were you live and drive. E.g. Hot Air vs Cold Air.
So if you are hearing 'knock' with 87 octane.
You either have engine issue already or sensor issue (may or may not get a code) or Air is factor.
 

Mountain Whiskey

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I'm done. Tried my best to explain. You have zero comprehension about how the PCM works. The manual also does not say the truck is "designed to run in 87" and literally says 89 is recommended for best performance. Which anyone with common sense would realize that is what it actually "designed" to use. Anything else is a compromise.

As for the Pulsar, once again, you have proven you have no clue what you are talking about. Have a good evening. You do you with your truck, and I will do me.
I am certainly glad you are done. The manual does say it is designed for 87 to 89. Read the 87 part. If you miss it, drop back and read it again. Read slow so it sinks in. One more time just for comprehension. Pause, let it sink in. That's better. It specifically says "designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having an octane range of 87 to 89". This does not say only use 89. It does not say use of 87 will damage your engine. It does not say "can". It does say "recommended for optimum performance" when referencing 89. What is that? For the yahoo's that want an extra .01 second on their 0 to 60 time? Woop. Perhaps, pulling a load, camper or boat, 89 might be better for this. Drive down the highway with plenty of zip? 87 works fine.....

The original post asked if better milage was to be had with a different octane gasoline. I think we know the answer is no, better milage vs cost is a loss.
 

CanRebel

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@Mountain Whiskey Technically speaking.
Octane is fuel stability. Higher number helps with detonation/knock.
Now a days all new engines will 'knock' for one or two cycles, until computer adjusts. Ford for example tells you this in their manual.
As well as few others. It is normal process.

Side effect of higher octane, if tuned for it, can produce higher HP/Torque. Doesn't mean you will get MPG, but it is possible.

 

theblet

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2021 Ram 1500 5.7HEMI eTorque. Has anyone has run 87 octane and noticed a significant change when switching to a higher octane? I know the manual says no lower than 89 but other than MPG potentially being impacted, I don't have any issues. Would possibly spend the extra $$ if I knew it would yield higher MPG's. Thanks.
The manual says no lower than 87 not 89. You’re good sir.
 

RAM Patriot

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@Mountain Whiskey Technically speaking.
Octane is fuel stability. Higher number helps with detonation/knock.
Now a days all new engines will 'knock' for one or two cycles, until computer adjusts. Ford for example tells you this in their manual.
As well as few others. It is normal process.

Side effect of higher octane, if tuned for it, can produce higher HP/Torque. Doesn't mean you will get MPG, but it is possible.

Good Article, Thanks for sharing I believe these two paragraphs from the article are pertinent to the discussion:

"Before electric computerized ignition was widely used, this knocking commonly occurred and could cause significant engine damage. Most modern engines have sensors to detect knocking. When detected, the computer delays the initial spark, which causes the controlled combustion to take place at a point when compression is not at its highest point. Although this eliminates the knock, it can cause the engine to run less efficiently.

A similar undesirable condition is called pre-ignition, when the fuel ignites on its own before the spark ignites it. Modern engine computers minimize this condition by controlling the timing of valves and fuel injection; however, this control mechanism can also come with a fuel-efficiency or emissions penalty."
 

Cajun_

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Good Article, Thanks for sharing I believe these two paragraphs from the article are pertinent to the discussion:

"Before electric computerized ignition was widely used, this knocking commonly occurred and could cause significant engine damage. Most modern engines have sensors to detect knocking. When detected, the computer delays the initial spark, which causes the controlled combustion to take place at a point when compression is not at its highest point. Although this eliminates the knock, it can cause the engine to run less efficiently.

A similar undesirable condition is called pre-ignition, when the fuel ignites on its own before the spark ignites it. Modern engine computers minimize this condition by controlling the timing of valves and fuel injection; however, this control mechanism can also come with a fuel-efficiency or emissions penalty."
and by less efficiently they mean less HP which is why you get more HP out of a tune that's made for higher octane.
 

Timeless

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So to add to this never ending thread, it might occur to some people that having a bit of buffer in the case of poor quality fuel might be a good thing.

So running 87 all the time does present this risk whereas running 89 or a mix close to this would perhaps give you a buffer to feel comfortable with.

A poor tank of sub par gas may dip below 87 which could then result in real knock/ping/detonation.

Just fuel for thought.
 

Buz

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Someone posted a video a while back with their 5.7 Hemi hooked up to a computer and looked at the timing with different octane gas.
You could clearly see the engine parameters preferred 89 over 87.
Maybe someone knows the vid I'm talking about and can repost?
 

Drivinfast247

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I think of it this way: 87 octane is the bare minimum for something to be able to be sold as a working fuel. The ~.30c more a gallon is a cheap insurance in the longevity of my vehicle.

It does suck fueling up every 5 days at $80 a pop, though!
 

HSKR R/T

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I think of it this way: 87 octane is the bare minimum for something to be able to be sold as a working fuel. The ~.30c more a gallon is a cheap insurance in the longevity of my vehicle.

It does suck fueling up every 5 days at $80 a pop, though!
There is 85 octane at higher elevations
 

OCD Solutions

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I've been tracking mileage data on vehicles since the mid 90's when I bought my first V10 and the dealer said it would get 14MPG or they would buy it back off me, lol.

A few months ago I decided to run 6 tanks of mid grade and capture the numbers for a solid comparison against the last 6 tanks of Reg.
The short answer is that while I did improve the mileage, I also increaed the cost per mile so in the end, it was a loss.
Performance is moot whith the cruise set at 80 for 3 hrs straight.
 

RAM Patriot

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I've been tracking mileage data on vehicles since the mid 90's when I bought my first V10 and the dealer said it would get 14MPG or they would buy it back off me, lol.

A few months ago I decided to run 6 tanks of mid grade and capture the numbers for a solid comparison against the last 6 tanks of Reg.
The short answer is that while I did improve the mileage, I also increaed the cost per mile so in the end, it was a loss.
Performance is moot whith the cruise set at 80 for 3 hrs straight.
I wonder what the cost comparison would be if you tracked the wear and tear on the engine and service cost.

Of course this only matters for those of us that plan on keeping the truck long term.
 

OCD Solutions

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I wonder what the cost comparison would be if you tracked the wear and tear on the engine and service cost.

Of course this only matters for those of us that plan on keeping the truck long term.
Do you track your idle time vs time under throttle? I hear Hemi's hate to idle.

Plan all you want, in the end, it will last as long as it will last and you still won't have any idea if could have run longer had you done one single thing different.
I've done everything wrong before and still made it to 327k miles on the stock motor and tranny and then done everything right and lost the motor at 47k.
So what really matters?
 

RAM Patriot

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Do you track your idle time vs time under throttle? I hear Hemi's hate to idle.

Plan all you want, in the end, it will last as long as it will last and you still won't have any idea if could have run longer had you done one single thing different.
I've done everything wrong before and still made it to 327k miles on the stock motor and tranny and then done everything right and lost the motor at 47k.
So what really matters?
Actually, all of our trucks monitor the idle hours versus drive time or "under throttle", and you are correct, the idle time is not good for these engines.

Idle Hours.png

There are pro's and cons with everything. 🆚 :unsure:

Yes, 89 octane gas cost more but the trucks runs better. 🚀

I notice not only an improvement in performance but also in MPG.

Therefore I can justify the cost in the long run.

To me the truck was less responsive with 87 octane, would ping on the occasional hill and I felt like the HEMI was taking a nap. o_O
 
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Buz

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The short answer is that while I did improve the mileage, I also increaed the cost per mile so in the end, it was a loss.
Performance is moot whith the cruise set at 80 for 3 hrs straight.
This I agree with 100%.
If I were 90% highway I would definitely not waste money on 89.
But I'm 90% in town and notice subtle increased acceleration smoothness with 89.
 

XmikeX

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Soooo after doing some reading and looking around it seems like 85 is a no go. I'm in Colorado and that is the common octane here, does one run the risk of damaging the vehicle if they run 85 or is it just from a performance perspective? I have ran some tanks of 85 and the truck didn't seem to really care and generally its 20-30 cents cheaper. Truck is still new to me and didn't even know it needed a certain octane until reading through here.

Not trying to start an octane war just want to clarify and know if I need to always run 87 or higher. I'm at altitude and read that lower octane is acceptable but want to make sure I'm understanding it correctly.
 

RAM Patriot

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Soooo after doing some reading and looking around it seems like 85 is a no go. I'm in Colorado and that is the common octane here, does one run the risk of damaging the vehicle if they run 85 or is it just from a performance perspective? I have ran some tanks of 85 and the truck didn't seem to really care and generally its 20-30 cents cheaper. Truck is still new to me and didn't even know it needed a certain octane until reading through here.

Not trying to start an octane war just want to clarify and know if I need to always run 87 or higher. I'm at altitude and read that lower octane is acceptable but want to make sure I'm understanding it correctly.
According to: https://www.fueleconomy.gov/feg/octane.shtml

What is 85 octane, and is it safe to use in my vehicle?​

"The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower—because it was cheaper and because most carbureted engines tolerated it fairly well. This is not true for modern gasoline engines. So, unless you have an older vehicle with a carbureted engine, you should use the manufacturer-recommended fuel for your vehicle, even where 85 octane fuel is available."
 

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