Question about fuel octane level.

[Dale A Bennett]

I was reading through the owners manual and noticed this Ram calls for 89 octane instead of the usual 87 on past year Rams. Why the difference and is it worth it? Thanks everyone.

 

[Wild one]

They always reconmended 89 in the hemi,with 87 being acceptable .

 

[Art_in_CO]

I used 87 octane for the first few months then switched to 85. Cannot tell any difference - power or mpg. Up here (6000+ ft. elevation), regular is 85 octane, mid-grade is 87 octane, but premium is still 91 octane.

 

[Zoe Saldana]

It needs it because of the high compression.

Use it.

You paid good money for that truck. Do you want to risk damage to save a few $

I was reading through the owners manual and noticed this Ram calls for 89 octane instead of the usual 87 on past year Rams. Why the difference and is it worth it? Thanks everyone.

 

[BossHogg]

Few topics will yield more opinions than octane, with most opinions touching on some truth with a large twist of false. Oil will bring the same results. If this thread continues, I'll take a large bucket of buttered popcorn, please.

 

[Dale A Bennett]

Lol ya sorry to start up a **** storm thread. Same thing would happen on the JL Jeep forum. Anyways I just noticed on this Ram via owners manual it calls for 89, and my past rams it called for 87, just was curious what the difference was for the bump. Anyways thanks everyone.

 

[Fatbob Frank]

Few topics will yield more opinions than octane, with most opinions touching on some truth with a large twist of false. Oil will bring the same results. If this thread continues, I'll take a large bucket of buttered popcorn, please.

Now do ethanol yea or nay!

 

[Zoe Saldana]

Two years and you are just reading the manual?????????????

Have you changed your oil yet?

I was reading through the owners manual and noticed this Ram calls for 89 octane instead of the usual 87 on past year Rams. Why the difference and is it worth it? Thanks everyone.

 

[Wild one]

Lol ya sorry to start up a **** storm thread. Same thing would happen on the JL Jeep forum. Anyways I just noticed on this Ram via owners manual it calls for 89, and my past rams it called for 87, just was curious what the difference was for the bump. Anyways thanks everyone.

My manual for my 14 says 89 is reconmended with 87 being aceptable. As far as i know,it's been that way since they went to vvt. I think you might have misread your old manuals.

 

[Dale A Bennett]

Two years and you are just reading the manual?????????????

Have you changed your oil yet?

No man it's a used truck i bought. Relax

 

[Dale A Bennett]

My manual for my 14 says 89 is reconmended with 87 being aceptable. As far as i know,it's been that way since they went to vvt. I think you might have misread your old manuals.

You are probably right just popped out at me for some reason.

 

[Wild one]

You are probably right just popped out at me for some reason.

A lot of guys do notice a bit of a power and milege increase using 91,you could try experimenting a bit with fuel,and see how the truck likes differant fuel octanes.The only stock 5.7 i own is my 300,and it definitely likes 91 over either 87 or 89,and gets about 1.5 mpg better milege over 89 and closer to 2 mpg better compared to 87.If you decide to experiment,run at least 2 tanks of the same fuel ,and it doesn't hurt to pull the battery posts off,when you fill up the 2nd time,to reset the engine adaptives and let the truck get the full benefit of the increased octane

 

[Farmer Fran]

Run 89

 

[rzr6-4]

Two years and you are just reading the manual?????????????

Have you changed your oil yet?

09 ram, 93 sierra, 98 moto guzzi, none of which had a manual when I bought them and I have no intentions of getting one. I also run 87 octane

I've run 89 and 87 octanes, with the 87 octane varying from 10% to 30% ethanol. I don't track milage close enough to know one way or the other but I've never noticed throttle response change or being down on power.

If I knew I was going to be hooking up to the 14K lb stock trailer, would I fill up on the 30% ethanol? Probly not. But other than that even under heavy loads I've never had an issue from various octanes/blends. Not just hearsay, but actual experience.

 

[Docwagon1776]

Short version:
5.7L will see some modest gains in power and fuel economy with 89 and maybe 91, depending on factors like elevation. Somewhere on here is a thread where someone did live data logging and showed how the octane changed how soon timing was pulled.

*now* is it is a big enough difference to matter? Probably not. Maybe if you're towing heavy and it's hot you'll be more likely to see/feel a difference. Just daily puttering around? Doubtful.

6.4L (truck) is not tuned the same and is 87 recommended per manual.

 

[Curmudgeon]

Comparing 87 vs 89 vs 91...

Paging @HEMIMANN - or is it @Hemi395 ? I can't keep 'em straight.

Too much Hemi in this gin joint.

 

[Wild one]

Short version:
5.7L will see some modest gains in power and fuel economy with 89 and maybe 91, depending on factors like elevation. Somewhere on here is a thread where someone did live data logging and showed how the octane changed how soon timing was pulled.

*now* is it is a big enough difference to matter? Probably not. Maybe if you're towing heavy and it's hot you'll be more likely to see/feel a difference. Just daily puttering around? Doubtful.

6.4L (truck) is not tuned the same and is 87 recommended per manual.

The truck 6.4 is a 1/2 point lower compression compared to the 5.7. The truck 6.4 is tuned to run on 87 octane at full load for 12 minutes.It also has a more robust piston then the 5.7 has,with the top ring land farther down on the piston,and a thicker piston top,so it'll handle 87 alot better then a 5.7 will. The 6.4 truck is 10:1 compression ratio , the 5.7 is 10.5:1 compression ratio ,the car/jeep 6.4 is 10.9:1 and has glass pistons compared to the truck 6.4. If you want to boost a stock bottem end naturally aspirated late model VVT hemi,the truck 6.4 is the better candiate for boost

 

[HEMIMANN]

Comparing 87 vs 89 vs 91...

Paging @HEMIMANN - or is it @Hemi395 ? I can't keep 'em straight.

Too much Hemi in this gin joint.

Eh?



What's the question? I think @Hemi395 did the datalogging on different octane gasolines. That's when I sat up and paid attention to how the ECM algorithms respond to knock sensing with ignition timing changes.

 

[Docwagon1776]

The truck 6.4 is a 1/2 point lower compression compared to the 5.7. The truck 6.4 is tuned to run on 87 octane at full load for 12 minutes.It also has a more robust piston then the 5.7 has,with the top ring land farther down on the piston,and a thicker piston top,so it'll handle 87 alot better then a 5.7 will. The 6.4 truck is 10:1 compression ratio , the 5.7 is 10.5:1 compression ratio ,the car/jeep 6.4 is 10.9:1 and has glass pistons compared to the truck 6.4. If you want to boost a stock bottem end naturally aspirated late model VVT hemi,the truck 6.4 is the better candiate for boost

Yeah, the easiest way to think of it for me was the 6.4L truck was designed with fleet use in mind. Lower cost of ownership/operation by using regular fuel and weighted toward longevity vs performance. It's got plenty of power to get work done, but obviously with the car version there's a lot left on the table as well. Heavier rotating mass spins up slower but is more durable, lower compression ratio hurts power but less strain, etc. The 5.7L was designed with individual consumers in mind and HP wars matter.

I'm incredibly impressed with mine, the 6.4L/8A is simply the best drive train overall I've had in a truck. It may not be the best in any one category, but it's just so good across the board. Don't get me wrong, I'm quite impressed with the 5.7L as well, but the 6.4L is just better. Kind of a shame the half ton never got the option.

 

[Wild one]

Yeah, the easiest way to think of it for me was the 6.4L truck was designed with fleet use in mind. Lower cost of ownership/operation by using regular fuel and weighted toward longevity vs performance. It's got plenty of power to get work done, but obviously with the car version there's a lot left on the table as well. Heavier rotating mass spins up slower but is more durable, lower compression ratio hurts power but less strain, etc. The 5.7L was designed with individual consumers in mind and HP wars matter.

I'm incredibly impressed with mine, the 6.4L/8A is simply the best drive train overall I've had in a truck. It may not be the best in any one category, but it's just so good across the board. Don't get me wrong, I'm quite impressed with the 5.7L as well, but the 6.4L is just better. Kind of a shame the half ton never got the option.

I know a couple guys who've dropped the truck 6.4 in their 1500's,and they're getting noticably better milege with the 6.4 compared to their old 5.7's,and both claim alot less downshifting from their 8 speeds when unloaded or when towing.On paper it looks like the truck 6.4 isn't a huge upgrade over the 5.7,but in the real world it turns out to be a hell'va upgrade,as the 6.4's torque curve blows the 5.7's torque curve into the weeds.I think they majorily screwed up,by not dropping the truck 6.4 into the 1500's