87 Octane is OK for 6.4L Hemi?

[sstoner911]

Page 477 in my owners manual

"FUEL REQUIREMENTS — GASOLINE ENGINE While operating on gasoline with the required octane number, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see a dealer immediately. Use of gasoline with a lower than recommended octane number can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty. Poor quality gasoline can cause problems such as hard starting, stalling, and hesitations. If you experience these symptoms, try another brand of gasoline before considering service for the vehicle. 6.4L ENGINE Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine. This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having a posted octane number of 87 as specified by the (R+M)/ 2 method."

The 6.4 in the high performance cars is a much different animal than the truck engines.

You won't get any pre-ignition and even if you did it would automatically pull timing much faster than you'd ever hear anything. The days of distributors and hearing a can of rocks in the engine due to improper timing (on stock engines) are long gone.

Run 87, save money, be happy. Don't overthink it.

The 6.4 and trans in the Scats is the same in the 2500s.

Same tuning. You can run 87 but you are doing a disservice to the 6.4 and the money you invested in it.

 

[Dave01]

The 6.4 and trans in the Scats is the same in the 2500s.

Same tuning. You can run 87 but you are doing a disservice to the 6.4 and the money you invested in it.

Definitely same engine sharing nearly all the same parts, but different tuning in the Ram's. At least this is what I've gleaned from my reading.

I honestly don't know if there is a right and wrong answer on this octane question, it will end up being personal preference.

 

[Darkside]

The 6.4 and trans in the Scats is the same in the 2500s.

Same tuning. You can run 87 but you are doing a disservice to the 6.4 and the money you invested in it.

The engine is the same size yes, but tuning is definitely not the same, the truck 6.4 is built for durability and long run times under load. The transmission is not the same, Scat pack has an 8HP70, the trucks have the 8HP75-LCV.

 

[Poolmonkey]

In podunk, I pump whatever is available and tow away. Always in the mountains (the entire state is mountain) and often in extreme heat, everything is fine.
With the Raptor, had CELs several times immediately after filling from middle of nowhere tanks that offer only one fuel of unknown octane…always ignored it.

 

[Jimmy07]

The 6.4 and trans in the Scats is the same in the 2500s.

Same tuning. You can run 87 but you are doing a disservice to the 6.4 and the money you invested in it.

Different trans between the two. The engine block is the same between the 6.4 BGE and SRT engines, but that’s where it ends.

 

[Docwagon1776]

Yes when it comes to the 6.4L. I had a Scatpack and the manual said 91 octane only. I am guessing they are tuned the same way for the HD trucks just as they are in the Scats.

You could try a lower Ocatane - but I bet you find it doesn't like it.

No. Not only is tuning *obviously* different for vehicles given the roughly 70hp difference between the two, the compression ratio is different at 10.9 vs 10.1 to 1 Compression ratio is the biggest driver of octane requirement.

The 6.4 and trans in the Scats is the same in the 2500s.

No, it isn't. Others have already addressed this.

The manual for my '21 calls for 87. Unless you increase the compression ratio or fiddle with the timing, absent some extreme elevation and temperature issues there's no reason to vary from that. 5.7s call for 89.

 

[sstoner911]

Different trans between the two. The engine block is the same between the 6.4 BGE and SRT engines, but that’s where it ends.

I see the HD truck uses a 8HP75-LCV vs the 8HP70 transmission - which is in the 1500 series.

If you have ever seen a Hemi 2500 race a Charger/Challenger scat - you would think its only weight of the vehicle

 

[sstoner911]

No, it isn't. Others have already addressed this.

But you couldn't resist - lmao

 

[JohnandDonna]

Yes when it comes to the 6.4L. I had a Scatpack and the manual said 91 octane only. I am guessing they are tuned the same way for the HD trucks just as they are in the Scats.

You could try a lower Ocatane - but I bet you find it doesn't like it.

The 6.4 Apache in the cars is not the same as the 6.4 BGE that is in the trucks. There are a lot of modifications between the two. The Apache is designed for speed, acceleration and horsepower. The BGE is set up for towing and durability. I use 89 octane in my truck.

 

[sstoner911]

The 6.4 Apache in the cars is not the same as the 6.4 BGE that is in the trucks. There are a lot of modifications between the two. The Apache is designed for speed, acceleration and horsepower. The BGE is set up for towing and durability. I use 89 octane in my truck.

They refer to the Hemi 6.4 as the apache no matter the chassis its in...

There may be other differences but the 6..4 is Apache across the board.

i.e Big Gas Engine is synonymous with the Hemi in the 2500 trucks...
Or 3500 in the odd ones I have seen ordered that way.

 

[Jimmy07]

They refer to the Hemi 6.4 as the apache no matter the chassis its in...

No. The Apache is the 6.4 that is in anything other than an HD Ram.
The BGE is the 6.4 that is used in Ram trucks.

 

[sstoner911]

No. The Apache is the 6.4 that is in anything other than an HD Ram.
The BGE is the 6.4 that is used in Ram trucks.

I may have confused apache and Bge swaps...I think some guys were using BGE blocks for various reasons to beef up the 392.

 

[sstoner911]

All in all...

You Hemi guys just spend the extra $20 bucks for better fuel...cheapskates

 

[Docwagon1776]

But you couldn't resist - lmao

Others addressed the transmission, so I didn't address that part... but nice try to quote me without context. Easier to bite back vs just admit you know jack **** about what you're talking about, right?

All in all...

You Hemi guys just spend the extra $20 bucks for better fuel...cheapskates

Different octanes aren't "better", they are different. As long as the vehicle isn't pulling timing to avoid pre-detonation, what advantage do you imagine higher octane fuel has for a motor?

When I had the 5.7 I ran 89. With my 6.2L Camaro, I run 93. On the Power Wagon I run 87. It has nothing to do with "cheap", it has to do with understanding what you're buying and why.

 

[sstoner911]

Others addressed the transmission, so I didn't address that part... but nice try to quote me without context. Easier to bite back vs just admit you know jack **** about what you're talking about, right?



Different octanes aren't "better", they are different. As long as the vehicle isn't pulling timing to avoid pre-detonation, what advantage do you imagine higher octane fuel has for a motor?

When I had the 5.7 I ran 89. With my 6.2L Camaro, I run 93. On the Power Wagon I run 87. It has nothing to do with "cheap", it has to do with understanding what you're buying and why.

Awww....look at you and your feelings.

Nope I know nothing.

 

[jadmt]

GEN III HEMI® Engine Quick Reference Guide Part IV

MORE CUBES AND MORE POWER: 2011 – 2021 6.4L/392 HEMI® V8 ENGINE So far in this series, we have covered the beginning of the great HEMI® engin...

www.dodgegarage.com

 

[Crusty old shellback]

The BGE does have similar heads as the hellcat. But both are different than what's on the Scat Pack 6.4.
They are 2 completely different engines.
Octane is just a representation of resistance to detonation. Higher the number, the slower it burns and harder to detonate.
With hight compression engines (13:1 and higher), which the BGE is not, you need a higher octane fuel.
Go watch the engine masters video I posted earlier to learn about octane.

 

[Docwagon1776]

Nope I know nothing.

We noticed, don't worry.

 

[Electronut]

I've been running 87 octane in my 2022 2500 6.4L 410 axle for about 10K miles. I recently switched to 89 it runs and sounds so much better I'm going to keep buying it. And I do try to buy top tier gasoline. I mostly use the truck to tow an 11k gvw 5th wheel

I just returned from our first big trip towing our 27' travel trailer. Used 87 octane 85% of the 1500 miles. No knocking at all. Can't even get 89 in NJ so on way home in Virginia I said what the hell let me try a tank of 89. Absolutely no noticeable difference. I actually may have lost 1 MPG using it since was tracking my performance. I consistently got an avg 10 Mpg towing our 27ft Airstream that has about a 7k lb. load plus gear in bed and 4 passengers but was through significant grade terrain in the Blue Ridge Mountains and also Great Smokey Mountains. On level grade with smooth acceleration I can get 11 MPG towing. Best I got so far without towing was 12.5 MPG but truck only has 2500 miles only thus far. This is with 4.10 rear as well. Will continue my testing.

Page 477 in my owners manual

"FUEL REQUIREMENTS — GASOLINE ENGINE While operating on gasoline with the required octane number, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see a dealer immediately. Use of gasoline with a lower than recommended octane number can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty. Poor quality gasoline can cause problems such as hard starting, stalling, and hesitations. If you experience these symptoms, try another brand of gasoline before considering service for the vehicle. 6.4L ENGINE Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine. This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having a posted octane number of 87 as specified by the (R+M)/ 2 method."

The 6.4 in the high performance cars is a much different animal than the truck engines.

You won't get any pre-ignition and even if you did it would automatically pull timing much faster than you'd ever hear anything. The days of distributors and hearing a can of rocks in the engine due to improper timing (on stock engines) are long gone.

Run 87, save money, be happy. Don't overthink it.

Agreed. I already had posted right from the manual that RAM recommends 87 in my 2022. The high performance cars is a totally different animal and they are tuned differently from the factory.

My 2008 Aspen with 5.7L Hemi needs minimum 91 which if you don't it does knock. I have a tuner which detunes and adjusts the timing so can take 87. It's now my daily driver so to save some money on fuel this is what I'm doing.

 

[ColoradoCub]

I've been running 85 (Colorado) in my 6.4's for years. Most of my usage is towing 8800# TT. Over the years I've tried 87 and 91 and never could tell the difference in power or mileage. I finally drove the truck on a 500+ trip empty, Speeds to 75, most speeds at 65, and over three high mountain passes. Evic read 18.7 but actual mileage was 18.26 I don't think I could beat that with the higher octane.

It’s amazing how many Hemi owners I know or have met here in Colorado that have no idea they are supposed to run Colorado mid grade which is 87, and they have been running 85 since their trucks were new with zero issues. Never made sense to me that that FCA doesn’t put something on the gas cap about the fuel grade like my wife’s Lexus has. Do they really think people are going to read the owners manual before pumping gas?