87 vs 89 octane

[ramffml]

2017 Ram Rebel, using 87 octane for years, with occasional fuel injector cleaner, trouble free, runs fine.

"runs fine" is ok, runs amazing is better. My truck runs the best on 91 its not even close. Ping is noticably less especially while towing, and it probably derates your truck by 15 hp by running 87 (Nissan actually gives two different power figures based on the octane and there is about a 10 to 15 hp difference IIRC, the hemi will probably be similar).

So the pinging is obviously better, I like to think I notice the power difference as well. Never noticed an MPG difference though because there are way too many variables for that, unless you always hand calc the exact same MPG you'll never notice the savings from 91.

I run the 91 due to the ping first and foremost, I want to keep that minimized. Power "gains" (or rather, "no losses") is a great bonus and if I save fuel too, so be it.

 

[Dusty]

I didn't think I had any hesitation a few weeks ago until after I cleaned the throttlebody.

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 102260 miles.

 

[Dean2]

"runs fine" is ok, runs amazing is better. My truck runs the best on 91 its not even close. Ping is noticably less especially while towing, and it probably derates your truck by 15 hp by running 87 (Nissan actually gives two different power figures based on the octane and there is about a 10 to 15 hp difference IIRC, the hemi will probably be similar).

So the pinging is obviously better, I like to think I notice the power difference as well. Never noticed an MPG difference though because there are way too many variables for that, unless you always hand calc the exact same MPG you'll never notice the savings from 91.

I run the 91 due to the ping first and foremost, I want to keep that minimized. Power "gains" (or rather, "no losses") is a great bonus and if I save fuel too, so be it.

Not sure what year your pickup is but I get zero ping on the jeep or the 2500, no matter what fuel i am using. If you have a post 2010 that pings there is something wrong with the vehicle. The computer should easily adjust to the lower octane, at least at 85 or above.

 

[ramffml]

Not sure what year your pickup is but I get zero ping on the jeep or the 2500, no matter what fuel i am using. If you have a post 2010 that pings there is something wrong with the vehicle. The computer should easily adjust to the lower octane, at least at 85 or above.

Every hemi pings, if you don't believe me, put a data logger on it, others have done so on YT. The user manual even says (paraphrasing) "a small amount of ping is normal".

 

[Retiring Don]

Octane doesn't create horsepower. What it does is the higher octane prevents pre-ignition and that is why higher compression, higher horsepower engines with a lot of timing advance need the 100+ octane gasolines, or flex fuels with methane in them. I run 87 octane in my '19 5.7l around town and 89 most of the time when towing my 6500 lbs travel trailer without any issues in 66K (37K towing) miles. When pulling my trailer in northeast states or California where the 89 octane was well over $4/gal I have used 87 octane without issues. You might see a slight decrease in mpg when running 87 octane because when under load the anti-knock sensor might retard the timing a bit to prevent pre-ignition but I would defy anyone outside of a controlled experiment on a closed track to quantify the loss.

 

[Wild one]

Every hemi pings, if you don't believe me, put a data logger on it, others have done so on YT. The user manual even says (paraphrasing) "a small amount of ping is normal".

You've been mentioning your truck pings alot on 87 octane,i almost wonder if you might not have an injector working properly.Google diesal shops in your area and see if any of them can flow test your gas injectors,as you shouldn't hear ping on 87 unless somethings not quite right

 

[ramffml]

You've been mentioning your truck pings alot on 87 octane,i almost wonder if you might not have an injector working properly.Google diesal shops in your area and see if any of them can flow test your gas injectors,as you shouldn't hear ping on 87 unless somethings not quite right

I noticed it almost immediately after purchasing it new. My brother has a new classic and he says it does it too. I cycle quite often and pass through 4 way stops once in a while, the amount of cars and trucks I hear ping as they're taking off is quite high, its a common occurrence across a range of cars and trucks.

I had a friend with me for a 5 minute ride who is a mechanic (not my mechanic though) and he didn't notice a thing even when I heard it a time or two on 91 yet.

I do want it professionally looked at, plugs (injectors is a good idea), logged via some software etc, right now I'm just short on time to be without it for a while and 91 seems to take care of it for the most part.

 

[turkeybird56]

This statement tracks. If an engine is tuned for 89 and no mods have been made, 91 would be negligible unless humidity or altitude became a factor.

Run 89 in MY 19 5th Gen. Neva run 87, I can tell the difference for sure and is tuned for 89. Heck, even my STIHL chain saw made for 89 octane, lol. I also run 89 in my MC, but a heck of a lot of difference between a boxer 6 cylinder and a 5.7 L Hemi. But this is just my preference and maybe the "butt" in the seat feeling. Also, a lot easier to stick with one grade when fueling gas cans for mowers and such, just for me my prerogative and perception and preference. IF PPL are ok and feel good with 87, hey go for it. Your ride. But I always buy top tier fuel, neva stop at Mom and Pop shops also.

 

[inuyasha-rules]

So I have to wonder, is the "regular" gas in your area really 87, because in my area it's 85. Higher elevations require less octane - lower air density means lower compression. My truck has a mild tune from the previous owner and I have to bump up to 91 when I go lower in elevation, but runs happily on 89 at 4,500'.

 

[97RedRam]

I know this is not scientific, but on my 97 with the 5.9 if I run 87 my truck has to downshift to go up some of these hills in Tennessee. When I run 90 to 93 octane the truck very seldom has to downshift going up those same hills. The knock sensor obviously is retarding the timing when I use 87. I always fill up at 1/2 tank and alternate between 87 and 93 with non ethanol.

 

[KeithP]

Low octane might contribute to preignition, but there’s no reason to associate that with hesitation.

And assuming it’s the same brand, very unlikely to be any difference between 87 / 89 in fuel additives impacting injector cleaning.

I’m sure the OP has accurately described his experience; but is it coincidence or cause and effect.

It could very well be coincidence but, I don’t know what else to attribute the hesitation to other than a fuel issue. Based on replies in this forum, this hesitation seems to be a unique issue isolated to my truck. Several weeks into using 89 exclusively and the hesitation has not returned. And, the change in fuels is the only change I’ve made.

 

[Tulecreeper]

Every hemi pings, if you don't believe me, put a data logger on it, others have done so on YT. The user manual even says (paraphrasing) "a small amount of ping is normal".

Mine doesn't. But my manual also says that.

 

[ramffml]

Mine doesn't. But my manual also says that.

You may not hear it ping, that's different than saying it doesn't ping. These are simple machines built on extremely precise equipment. Barring any equipment failures (like broken injectors or sensors), the same inputs will lead to the same outputs.

 

[Tulecreeper]

You may not hear it ping, that's different than saying it doesn't ping. These are simple machines built on extremely precise equipment. Barring any equipment failures (like broken injectors or sensors), the same inputs will lead to the same outputs.

Isn't that like saying, "If a tree falls in the forest but I don't hear it, why would I care?" Or, you know, something like that.

 

[ramffml]

Isn't that like saying, "If a tree falls in the forest but I don't hear it, why would I care?" Or, you know, something like that.

Well, it's more like saying "I didn't hear a tree fall in the forest so therefore it didn't fall".

I guess anything is possible, maybe my hemi is broken? But I'm just suggesting that "I don't hear it" doesn't mean it's not doing it. You could of course be right that it's actually not doing it.

 

[Tulecreeper]

Well, it's more like saying "I didn't hear a tree fall in the forest so therefore it didn't fall".

I guess anything is possible, maybe my hemi is broken? But I'm just suggesting that "I don't hear it" doesn't mean it's not doing it. You could of course be right that it's actually not doing it.

Oh, I fully agree with you that it very well may be doing it. But if I don't hear it, and it's not hurting anything, does it matter? I'm really asking. I used to be a half-assed shade tree mechanic but I gave that up when all this new-fangled 'puter stuff showed up. You know, digital radio dials, fuel injection, electronic ignition, that stuff.

 

[Dean2]

Well, it's more like saying "I didn't hear a tree fall in the forest so therefore it didn't fall".

I guess anything is possible, maybe my hemi is broken? But I'm just suggesting that "I don't hear it" doesn't mean it's not doing it. You could of course be right that it's actually not doing it.

ANY motor that pings constantly is being damaged. Ping is caused by pre-detonation, which means the charge is firing BEFORE it should be. That puts a lot of bad stress on a motor. If you can hear your engine pinging all the time you best get that fixed or you are going to need a new motor. The ping in the owners manual is referring to an odd occaision where you might hear a BIT of pinging under the right conditions. It is NOT saying ping is normal.

 

[Wild one]

I noticed it almost immediately after purchasing it new. My brother has a new classic and he says it does it too. I cycle quite often and pass through 4 way stops once in a while, the amount of cars and trucks I hear ping as they're taking off is quite high, its a common occurrence across a range of cars and trucks.

I had a friend with me for a 5 minute ride who is a mechanic (not my mechanic though) and he didn't notice a thing even when I heard it a time or two on 91 yet.

I do want it professionally looked at, plugs (injectors is a good idea), logged via some software etc, right now I'm just short on time to be without it for a while and 91 seems to take care of it for the most part.

Another thing to look into might be your knock sensors,it's not unheard of to have a knock sensor not quite up to par.If you have one that's slightly insensitive that would contribute to a ping situation.

 

[ramffml]

ANY motor that pings constantly is being damaged. Ping is caused by pre-detonation, which means the charge is firing BEFORE it should be. That puts a lot of bad stress on a motor. If you can hear your engine pinging all the time you best get that fixed or you are going to need a new motor. The ping in the owners manual is referring to an odd occaision where you might hear a BIT of pinging under the right conditions. It is NOT saying ping is normal.

Pre-detonation can be very damaging, if you're getting that then you're engine is done very shortly.

I just have detonation, the difference being when it occurs in the travel of the piston. Pre-detonation occurs before top dead center, before ignition has started, detonation occurs after or after the ignition has begun. It's more of an explosion vs a smooth burn or a small secondary light up. This is not damaging in small amounts.

Both forms can be heard as "ping", only pre-detonation happening before TDC is the damaging "non normal" kind. Detonation happens frequently across many engines.

 

[Light299]

I'd point out it's more complicated than just "detonation before TDC is damaging". 0.5 degree before TDC won't damage anything - flame front propagation and combustion time need accounted for. There's a reason the plugs fire BEFORE TDC.

Another depends on what the engine is doing as well - spark advance changes quite a bit from idle to 4500rpm and under different load conditions. That's why Octane is an average of RON and MON.

Temperature is another huge factor, idling in summer traffic is much more difficult for the computer to handle than highway speed in winter.

If you use a data logger, you'll see even with 89 there will be some knock - particularly at load and low RPM. But remember, that's what the neural net in the ECM is tuning for - its adjusting spark, cam phasing, and injection events to always keep the engine right on the edge of detonation. And you don't know where the line is till you cross it....