Better MPG with higher octane?

[mmondich]

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.

 

[Cajun_]

I found that to be true also with 91 cornless. For those of you that would like to try it, here is link to stations in US & Canada that sell cornless gas

Pure-gas.org - ethanol-free gasoline in the U.S. and Canada

Pure-gas.org is the definitive web site listing stations that sell pure gasoline in the U.S. and Canada.

www.pure-gas.org

gas without the cob

 

[BigBlueBeast]

I run 87 mostly I have run 89. I have noticed no real gain from 89. I figure if I am gonna pull something i'll run 89. I don't notice any difference in acceleration or anything between the fuels. I also haven't noticed any knock or any poor performance with 87

 

[theblet]

I run 87 mostly I have run 89. I have noticed no real gain from 89. I figure if I am gonna pull something i'll run 89. I don't notice any difference in acceleration or anything between the fuels. I also haven't noticed any knock or any poor performance with 87

Same here. I run 87 if I’m not towing heavy

 

[NavyChief]

The station close to me has 110 as I’m by the racetrack. I put their 91 in the bike but haven’t tried 89. I might give it a try to see what happens.

 

[HSKR R/T]

I like reading this! A 2,400 round trip to Florida hauling a 14' wedged cargo trailer yielded me only 8.4 MPG loaded, 8.9 MPG return trip and empty. I was using 87 and every one in a while I experienced some knocking, but not enough to be annoying.

By the time you notice/hear detonation, it's already doinf damage, and the PCM has already started pulling timing to try and prevent it. If you can hear knocking from the lower octane, that should be your first sign to switch to higher octane.

 

[HSKR R/T]

Truck is tuned to run 89. Due to the presence of knock sensors on the engine, Ram says you "can" run 87 because the PCM will just pull timing to prevent knock, meaning less performance. Just because you don't notice it SOTP doesn't mean performance isn't being effected. And if you are audibly hearing knock, that is damage being done inside the combustion chambers. Long term, that will be shortened engine life.

I run 91 non-ethanol, mainly because it's easy to get in my area, and with the Pulsar installed in the truck, it recommends 91+ fuel. I don't care about price difference. I didn't buy this truck for it's fuel economy, I run what is best for the engine.

As far as different brands, the only difference is the detergent package added when the tanker trucks deliver it to the station. Every gas station in a certain region gets it's fuel from the same pipeline. It's also good to switch brands every now and then for the different detergent package to help keep engine cleaner. You will get different fuel mileage from different brands. But it's about as significant as running different octanes. When I was in Navy stationed in Cali, and racing my Dakota I always got better times at drag strip running 76 brand, but it have worse fuel economy. Shell gave me best fuel mileage, but was slower at the track. Usually ran cheaper fuel when just daily driving, and only filled up with the 76 when going to track, or She'll when making long road trip. And that's because there was a 20-30 cent per gallon difference between quick trip and shell/Chevron even on same octane.

 

[Mountain Whiskey]

Or.... Just because it says you "can" run 89 does not mean that is what it is tuned for. It may mean that it is tuned for 87 like most of America runs, and in cases where optimal performance is needed the PCM advances to accommodate the use of 89.

 

[HSKR R/T]

Or.... Just because it says you "can" run 89 does not mean that is what it is tuned for. It may mean that it is tuned for 87 like most of America runs, and in cases where optimal performance is needed the PCM advances to accommodate the use of 89.

Owners manual doesn't say you "can" run 89, it says 89 is the recommended octane for optimal performance. Only reason you are able to run 87 is due to the knock sensors allowing the PCM to detect detonation and pull timing to prevent serious problems. And even with that, several in this thread, and many others throughout the forum, report audible detonation when using 87. Which isn't good for the engine

 

[Mountain Whiskey]

Owners manual doesn't say you "can" run 89, it says 89 is the recommended octane for optimal performance. Only reason you are able to run 87 is due to the knock sensors allowing the PCM to detect detonation and pull timing to prevent serious problems. And even with that, several in this thread, and many others throughout the forum, report audible detonation when using 87. Which isn't good for the engine

For what the owners manual is worth, it does not say any of the things you assume. It does say that the engine is "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." In other words 87 is fine to use. It does not say that the truck will struggle to retard the timing and you are destroying your engine using 87. If yours says that, please put it up.

It goes on to mention at the end that 89 is recommended for optimal performance. This being better than satisfactory performance in some way. Two points is not much difference in the gasoline world. If it was, race fuel would be 94 octane and call it good. As you know it is much higher because the detonation happens much earlier in race engines.

You are far overthinking a mass produced vehicle made to meet the different driving habits and conditions from grampa at sea level in Florida to Jonnie Hotrod in Denver. It covers a pretty broad spectrum.

On a forum you hear much more negative griping than positive talk. Most come just to find answers to problems. I would believe that yes, .00001% of the trucks produced might ping or have a need for 89. It is probably good if towing a load. The pcm likely adjusts the timing to accommodate this. If normal day to day driving is ok on 87, then everything is good using it. You can rest assured that the world will not end if you use 87 octane gas.

If you want to spend more on 89 because it gives you the warm and fuzzies, do me a favor. Please use ExxonMobil as this is the energy stock I own the most of.

 

[theblet]

87 is fine. Use 89 for max performance. Not that hard to understand.

 

[silver billet]

The knock sensors are reactive. That means the knock occurs first, then the computer reacts. This is like holding your hand over a candle; the burn occurs first, then the pain/nerves kick in, then you react by pulling your hand away, but the damage is still there. Ideally your hand sits far enough away that the damage doesn't happen in the first place (89+).

How much actual damage is there? I don't know, but it can't be good. Knock is an ugly sound. Saving $5 to $10 every 2 weeks doesn't seem worth it to me in a $50,000 truck.

So looking at this as "less performance" vs "max performance" is incorrect really, that gives the impression that you're fine running with less performance if you don't need it.

In reality, the choice is "slight damage" vs "less slight damage", I think that gives a better perspective on what we're doing with the octane. Yes you also get better performance and possibly mpg, but the real factor is damage... how bad is it to run 87??

 

[Mountain Whiskey]

87 is fine. Use 89 for max performance. Not that hard to understand.

^^^^^ This sums it up fine.

Those that worry can use 89 for fun and feel good. The real worrywarts can keep the truck in a climate controlled storage unit, wrapped in fine linens only to be touched while wearing white cotton jewelers gloves. Never to be started, oiling down the cylinders and gently turning by hand each year. Don't forget to coat all the hoses and seals with some 303 protectant or similar!

 

[silver billet]

Alternatively, those that drop $50,000 on a new truck and then clinch their butt over $10 bucks extra every few weeks can sit at home, proud and content over that horde of cash they're really saving now!

Bonus points for when you mod your truck to kingdom come but can't afford proper gas, the logic on those decisions are ... well, it's something.

 

[SacRebel]

Simple answer is no. That’s not how higher octane works.

 

[Mountain Whiskey]

Silver, as you are burning cash for fun, please use ExxonMobil. I appreciate the stock bump.

 

[HSKR R/T]

For what the owners manual is worth, it does not say any of the things you assume. It does say that the engine is "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." In other words 87 is fine to use. It does not say that the truck will struggle to retard the timing and you are destroying your engine using 87. If yours says that, please put it up.

It goes on to mention at the end that 89 is recommended for optimal performance. This being better than satisfactory performance in some way. Two points is not much difference in the gasoline world. If it was, race fuel would be 94 octane and call it good. As you know it is much higher because the detonation happens much earlier in race engines.

You are far overthinking a mass produced vehicle made to meet the different driving habits and conditions from grampa at sea level in Florida to Jonnie Hotrod in Denver. It covers a pretty broad spectrum.

On a forum you hear much more negative griping than positive talk. Most come just to find answers to problems. I would believe that yes, .00001% of the trucks produced might ping or have a need for 89. It is probably good if towing a load. The pcm likely adjusts the timing to accommodate this. If normal day to day driving is ok on 87, then everything is good using it. You can rest assured that the world will not end if you use 87 octane gas.

If you want to spend more on 89 because it gives you the warm and fuzzies, do me a favor. Please use ExxonMobil as this is the energy stock I own the most of.

No assumptions, and you pretty much repeated what I said as your post went on. Even verified that the owners manual does in fact say what I said about 89 being recommended for optimal performance. Even saying that the PCM retards timing in order to use 87 octane. Not overthinking anything. Just actually know how the PCM operates and how octane levels work.

 

[Mountain Whiskey]

No assumptions, and you pretty much repeated what I said as your post went on. Even verified that the owners manual does in fact say what I said about 89 being recommended for optimal performance. Even saying that the PCM retards timing in order to use 87 octane. Not overthinking anything. Just actually know how the PCM operates and how octane levels work.

Many people understand how octane levels work and how the pcm advances timing to account for the slower burn of the more expensive gasoline that is not needed under normal driving. I pointed out that nothing is said of the timing being retarded, you are the one that theorized this on your own. I typed this a little slower so it is easier for you to read this time.

It is comical that some believe their mass produced made in Mexico motor is some miracle of nanotechnology that won't run on regular gas. Hey, if ya got it, burn it! You can't take it with you.

 

[HSKR R/T]

Many people understand how octane levels work and how the pcm advances timing to account for the slower burn of the more expensive gasoline that is not needed under normal driving. I pointed out that nothing is said of the timing being retarded, you are the one that theorized this on your own. I typed this a little slower so it is easier for you to read this time.

It is comical that some believe their mass produced made in Mexico motor is some miracle of nanotechnology that won't run on regular gas. Hey, if ya got it, burn it! You can't take it with you.

So you are saying the PCM is somehow smart enough to advance timing for higher octane(not true) but doesn't retard timing based on knock sensors for lower octane? Do you hear yourself talk?

 

[Mountain Whiskey]

So you are saying the PCM is somehow smart enough to advance timing for higher octane(not true) but doesn't retard timing based on knock sensors for lower octane? Do you hear yourself talk?

Saying it does not retard when it is not needed. You know, like when running perfectly fine on regular gas. Just because you got a POS lemon that knocks, pings, shakes and rattles does not mean all do.

Do you even understand your own nonsense? Like I said, if ya got it burn it. It might make you feel better.

 

[HSKR R/T]

Saying it does not retard when it is not needed. You know, like when running perfectly fine on regular gas. Just because you got a POS lemon that knocks, pings, shakes and rattles does not mean all do.

Do you even understand your own nonsense? Like I said, if ya got it burn it. It might make you feel better.

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.