Question about fuel octane level.

[Wild one]

You are nuts. Nowhere in your manual does it state that you can use lower octane at higher altitudes. Since the days of electronic ignition, altitude does not matter! Many stations in my state of NM use 66 for regular and 88 for
midgrade. No delta in price with the few stations that use 87 and 89. Amazing how many people pay the same for a lesser product, also like you, thinking altitude matters. And make sure you use Top Tier.
You paid too much for a truck to try to save a few dollars.
By the way, I have won many bets with people claiming altitude matters.

Well you're wrong.Higher altitude has less barometric pressure,so the engine doesn't have the same amount of air pressure it can access to fill the cylinders,so consequently it doesn't create the same running cylinder pressure,and it doesn't require the same amount of octane to prevent detonation. The engine sucks in air ,and the more outside air pressure aka barometric pressure it has to work with,the more oxygen it can suck in. Ask any athlete,and altitude affects their preformance big time,an engine is no differant,it has less oxygen and air pressure to with work at altitude,and consequently needs less octane.Cylinder pressure affects octane requirements,and i don't think you're grasping that fact. You can actually tell it by doing a compression test,an engine at sealevel,creates more cylinder pressure on a compression test,then it does at say 5,000ft altitude
That's why a nitrous car doesn't fall off as much at altitude as a blown car or naturally aspirated car does,as nitrous creates it's own oxygen

 

[Hawk1775]

The only "difference" that I've ever noticed with my RAM's with the Hemi is ARCO. They knock and sputter horribly with it; never again... Couldn't get threw that tank fast enough. LMBO

 

[Gary Fields]

My owners manual says the same thing. I've run it on 87 and 89 with no difference noted either in drivability or mileage. I buy the 87 and smile. My other car, and Acura wants 91 Premium for a 10.3 to 1 compression rating. While on East Jesus Nowhere the two stations were out of all grades except 87. Car ran OK, not as zippy, but lost about 20% in fuel economy. It backs off the timing when you use regular.

 

[Wild one]

My owners manual says the same thing. I've run it on 87 and 89 with no difference noted either in drivability or mileage. I buy the 87 and smile. My other car, and Acura wants 91 Premium for a 10.3 to 1 compression rating. While on East Jesus Nowhere the two stations were out of all grades except 87. Car ran OK, not as zippy, but lost about 20% in fuel economy. It backs off the timing when you use regular.

Just an FYI your 5.7 is 10.5:1 compression ratio,which is higher then your Acura.It also utilizes variable valve timing which advances the cam at low rpm,to build cylinder pressure,and basically cylinder pressure is what creates torque.For $hit$ and giggles you should try a couple tanks of 91 and see what happens

 

[GCS_PowerWagon]

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.

2023 Power Wagon with 6.4L hemi.
My manual says 87 octane.

 

[MrFigs]

Going back to what Hemimann said about plant mixed 89 vs gas station mixed 89, I could see some variation in the gas station mix. I don't know where you are but many stations where I am you almost never see a pump tech out, and here the only routine testing is that at 17C (or is it 15C,whatever you get the point) you get 1L when it says you get 1L. I've never heard of any station doing testing to make sure you're getting 89 vs 88 or 90.

All that said, on my '12 1500 I run 87, mostly from Costco. I have a BullyDog tune on, just a default, no performance tune for 87 I don't run the ECO tune 'cause BullyDog says you shouldn't tow on that one, and the performance tune says 91 only, and the MPG/Butt Dyno never really noticed much of a difference on the performance tune. On the Reg tune I'd towed 1500lbs all the way up to 20,000lbs(Ya, I know i know, I asked for 2 yards of gravel and the quarry filled the trailer, which had realllly good brakes on it) running 87 octane.

I've had my '12 since Spring '14. I have the hemi tick, I've done the manifolds, I don't see any sparkle in my oil, I use mobil 1 about 300-500km after the truck tells me it's time to change oil, it seems to take idle time and load into account since I did 13,000km highway once before it binged and once after working the truck hard with a bunch of idle time it binged at 5000km. Anyhow, it still has all the low end grunt but i've been noticing it's struggling a bit at highway speeds loaded and unloaded, is that fuel related, or cam related, I don't know I'm neither a mechanic nor engineer.

 

[Wild one]

2023 Power Wagon with 6.4L hemi.
My manual says 87 octane.

Your 6.4 is noticably differant compared to a 5.7 in regards to fuel requirements,it has a 10:1 compression ratio,while the 5.7 has a 10.5:1,and your 6.4 is tuned to run at full load for 12 minutes on 87 octane,you run a 5.7 at full load on 87 for 12 minutes,good chance you might have a few engine issues at the end of the test

 

[Sherman Bird]

Ha ha - ideal doesn't exist, which is what my rants were about.

Ideal octane for THE EXISTING STOCK ECM ALGO is 89 dedicated octane - not a blend of pure 87 octane and pure 91-ish octane (whatever the required ratio to "average" 89 octane).

Since I'm an engineer and can't help living in a fact-based world, I use whatever higher octane (without higher alcohol level) is available. Here in Minnesota it seems to be 91 pure octane (@ 10% ethanol). Other states offer higher octane, 92 or 93, due to different refineries in their area. I always try to buy Top Tier brands, they have extra PEA detergent added to keep intake valve lands and injector nozzles clean. We have few left here, most brands pulled out of our flyover country (more expensive to ship to).

So I carry a measuring bottle of PEA (Red Line Sl-1) with me for when I need gas and there's no Top Tier station around. Ratio is 1 ounce extra per 15 gallons non-Top Tier gasoline.

The automotive world has really gone to hell the past 15 years. We are all trying to band aid our way forward.

What are the engineer specs on them band-aids? Hmm?

 

[Dusty]

The problem is that you cannot tell if the knock sensor can retard the timing enough to prevent preignition. The only way to tell is sound, and you would not hear it over the engine noise.

The knock sensor is no more than a bell that goes off when knock is detected. The amount of timing reduction is based on the PCM getting a knock signal, so the knock sensor only determines when knock is detected. If knock persists it's the PCM that keeps cutting back timing until the knock signal stops.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 135034 miles.

 

[Docwagon1776]

I'm not sure any of the mechanicals matter. Modern vehicles have much more sophisticated control of timing. Most can kick timing back far enough to safety operate with octane below the manufacturers minimum.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 134959 miles.

It's not just about damage control, in which you are correct in that the modern vehicles will pull timing before it starts hammering the piston enough to damage anything. Pulling timing isn't cost free, though, you're not using as much of the energy of the combustion process to actually move the vehicle down the road. You need more fuel to make the same power, in other words.

As a stark example, it's why the HO Hurricane is rated to tow less than the SO, it gets too hot and has to pull timing to not go into meltdown mode, which means more fuel is required, which produces more heat, which requires more timing retardation, and it spirals. The more powerful engine can't tow as much because it had to pull timing earlier.

 

[Dusty]

It's not just about damage control, in which you are correct in that the modern vehicles will pull timing before it starts hammering the piston enough to damage anything. Pulling timing isn't cost free, though, you're not using as much of the energy of the combustion process to actually move the vehicle down the road. You need more fuel to make the same power, in other words.

As a stark example, it's why the HO Hurricane is rated to tow less than the SO, it gets too hot and has to pull timing to not go into meltdown mode, which means more fuel is required, which produces more heat, which requires more timing retardation, and it spirals. The more powerful engine can't tow as much because it had to pull timing earlier.

You are absolutely correct.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 135034 miles.

 

[Sherman Bird]

This is where I was going. There are different levels of alkylation of the hydrocarbons that create the resistance to detonation. It's not dumping additives in, with the exception of alcohols.

I'm not going to argue anymore about it. I said what I said, from what I know about the different molecular construction. That is all.

.... and just think! My late Paternal grandfather used to tell me stories about replacing one cell in a battery, the advent of electric starters, and how, when he first saw an electric starter on a car, it was a huge "WOW".
He told me how "neat-o" it was when aluminum pistons came on the scene to replace those clunky cast iron ones...
And he told me how they would burn coal oil and kerosene in their cars! Compression ratios in the 4.5:1 range, split rim wheels that killed/ maimed....

And here we are today gobbling over hairsplitting octane, hydrocarbon, molecular stuff!
Truth be told, most folks just buy whatever's cheapest!

 

[turkeybird56]

.... and just think! My late Paternal grandfather used to tell me stories about replacing one cell in a battery, the advent of electric starters, and how, when he first saw an electric starter on a car, it was a huge "WOW".
He told me how "neat-o" it was when aluminum pistons came on the scene to replace those clunky cast iron ones...
And he told me how they would burn coal oil and kerosene in their cars! Compression ratios in the 4.5:1 range, split rim wheels that killed/ maimed....

And here we are today gobbling over hairsplitting octane, hydrocarbon, molecular stuff!
Truth be told, most folks just buy whatever's cheapest!

I just stay with top tier Shell. Once in a blue moon put in Sunoco. ALSO I know HEB not the highest top tier, but I run HEB 89 or top off with 93. Wateva I can get that is in that range. I STAY away from Mom and Pop pumps.

SHERM: I had a 67 SS, 396, 3 on the tree, when I was a kid, no money. SO whenever I parked, always parked up on an angle, rear end in so I could let roll and pop clutch in 3rd, no money for battery replacement, those were the days.

 

[Sherman Bird]

I just stay with top tier Shell. Once in a blue moon put in Sunoco. ALSO I know HEB not the highest top tier, but I run HEB 89 or top off with 93. Wateva I can get that is in that range. I STAY away from Mom and Pop pumps.

SHERM: I had a 67 SS, 396, 3 on the tree, when I was a kid, no money. SO whenever I parked, always parked up on an angle, rear end in so I could let roll and pop clutch in 3rd, no money for battery replacement, those were the days.

I owned a 1964.5 Mustang with a 4 speed and a 260 V-8. That was one rare 'Stang in that it had a generator. One day at work, some mouth breather stole my new battery. So, I got a couple of the guys to help me after I wrapped the battery terminals in rags and turned on the key, to push start it!
I drove straight over to a Pettigrew-Smith Auto parts store and bought a battery. Can't do THAT today!

I run only Texaco (Chevron) 87 in my Lexus daily driver.

 

[turkeybird56]

I owned a 1964.5 Mustang with a 4 speed and a 260 V-8. That was one rare 'Stang in that it had a generator. One day at work, some mouth breather stole my new battery. So, I got a couple of the guys to help me after I wrapped the battery terminals in rags and turned on the key, to push start it!
I drove straight over to a Pettigrew-Smith Auto parts store and bought a battery. Can't do THAT today!

CAN U imagine the cascade of bells, whistles and alarms and PID's sparked out if you tried to run somewhere on a generator/alternator only on one of these new RAMS? ? Be like Rockefeller Center XMAS tree, LOL.

That be like the old Chevy test, where you start vehicle, pull Negative cable and if vehicle still run, You knew your alternator was good, LOL. Been a minute since I heard of that old trick, hee hee. And as U know, it works, tho not now, LMAO.

 

[Sherman Bird]

CAN U imagine the cascade of bells, whistles and alarms and PID's sparked out if you tried to run somewhere on a generator/alternator only on one of these new RAMS? ? Be like Rockefeller Center XMAS tree, LOL.

That be like the old Chevy test, where you start vehicle, pull Negative cable and if vehicle still run, You knew your alternator was good, LOL. Been a minute since I heard of that old trick, hee hee. And as U know, it works, tho not now, LMAO.

Yeah, but you are not able to start a car with no battery by pushing it if it had an alternator, because there is no residual magnetism. such as my generator had. That's why I COULD push start that old Mustang in spite of the battery being gone. Driving it to the parts store was a challenge, because I could not turn on wipers, lights, or any other load, lest the engine die at idle.
So, I used hand signals and was happy that it was early enough in the evening that it was still light, and there was no rain!

 

[turkeybird56]

Yeah, but you are not able to start a car with no battery by pushing it if it had an alternator, because there is no residual magnetism. such as my generator had. That's why I COULD push start that old Mustang in spite of the battery being gone. Driving it to the parts store was a challenge, because I could not turn on wipers, lights, or any other load, lest the engine die at idle.
So, I used hand signals and was happy that it was early enough in the evening that it was still light, and there was no rain!

Neva tried starting by "pushing" w/o a battery installed, the battery was just shot, LOL. Do think the 67 had an alternator unda the hood. Those were the days spit, polish and wire U could keep things running, lol. ADMIT, all the niceties now are great, but as U said, no way U could do the old stuff today.

 

[Compu-Doc]

Frieburger and EMs are GOD
Nuff said...

 

[Dusty]

I'm old enough to remember when Chrysler products used left hand threaded bolts on one side, right hand threaded bolts on the other to mounted the wheels, two wheel cylinders per brake, and many cars had a separate starter pedal.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 135060 miles.

 

[Riccochet]

Straight from my 2020 owners manual. I don't want to "hear a light knocking sound from the engine".