Does 87 octane vs 89 octane really make a difference?

[south7west]

I've been running the recommended 89 octane, but I was curious on whether or not I'm spending the $8~ on nothing. I am currently getting roughly 15 - 16 mpg city driving.

 

[GhostCost]

Octane isn't mileage. It's anti-knock. think "smooth explosion vs. two firecrackers tied together. I get clattering (two firecrackers) on some 87 octane pumps, depending on the blend they happen to get delivered. With 89, I don't. YMMV

 

[south7west]

Octane isn't mileage. It's anti-knock. think "smooth explosion vs. two firecrackers tied together. I get clattering (two firecrackers) on some 87 octane pumps, depending on the blend they happen to get delivered. With 89, I don't. YMMV

Alright, I do now remember someone else on this forum saying the same thing about the truck knocking on lower octanes. Thanks!

 

[daveray9]

I did a hand calculated milage analysis for 87 for 2 weeks then 89. Posted it somewhere in here on someone elses thread. I got about 2mpg less on 87, and like he just said... didnt run as smooth. That being said Im running a 93 tune now and will probably never go back. Its about 4dollars more every time I fill up.. which is less than a good coffee.

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[gdawg55]

I run both octanes and can’t really tell much difference. Haven’t noticed any knocking with 87. I usually run 2 tanks of 89 to one tank of 87. If I’m filling up at Sams it’s 93 or 87. Use both here as well.

 

[Wild one]

I've been running the recommended 89 octane, but I was curious on whether or not I'm spending the $8~ on nothing. I am currently getting roughly 15 - 16 mpg city driving.

I'd hazard a guess the majority of trucks are filled up with 87,lol. I run 87 in my wifes 2016 5.7 Challenger which is the same as the trucks,89 reconmemded but 87 acceptable.Car runs the exact same numbers at the track on 87 as it does on 89,and actually slows down if I fill it up with 94.It also gets better milege on 87,as 87 is cleaner fuel.The additives added to increase octane numbers,don't burn worth ****,and will slow the combustion chamber burn down.I had an uncle who was a chemist with Mohawk for years,and he used to describe high octane fuel as "dirty" fuel because the additives don't burn all that great compared to gasoline

 

[roadrnnr]

I've run mine on 87 since new. No Knock and runs perfect. Everynow and then I will throw in an 89 tank and never notice any differance.
50k miles

 

[guru1ofatl]

The stock knock sensor calibration on these engines is extremely sensitive which leads me to believe that they went aggressive on the part throttle timing tables and rely on knock retard to protect the engine. The fact that they suggest 89 octane for best performance seems to confirm this. You can see a significant amount on short term knock when the intake temperatures go above 100*F running 87 octane. Add load and the AC running and the amount of timing pulled only gets worse. If I was still running stock I would consider running higher octane in summer and lower in winter.

It is worth mentioning that the sensors will measure knock when none is heard by the driver.

 

[Jrod]

Three RAM’s, all 87 octane, never had an issue, all have ran smooth as butter, average 14.5 city,hwy, can get as high as 21.5 on long road trips with flat roads and light wind even with my current mods.

 

[Tim Garceau]

Huge variables in modern gasoline, quality top tier fuel without ethanol is best regardless of the 87/89 debate. Typical pumps mix 87 with their premium to achieve the 89 ratio to save an underground tank. This is usually not regulated ala you might get 87.1 octane but pay $.50 more per gallon. (state dependent)

I go through this with my 2 strokes every year, carry testing strips on the trails so I know where to be on timing. Nothing more demoralizing than burning down a piston because of stale fuel.

 

[indept]

87 normally, sometimes half & half 87 & 93, no noticeable difference in mpg or performance. Runs smooth.

 

[QwikKota]

I am running an Edge Pulsar with 87 octane in high temps and I do not detect any knock. Do those of you that hear/feel pinging have a lot of miles?

ETA: I keep mine in level 6, +15hp mode.

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[Sheapdog]

I switched to 89 from 87 and am getting about 1-2 mpg better. Although it coincided with me using a redline fuel system cleaner, oil catch can, and redline 5w30 oil. Not sure anything had had to do with one thing or another. Just don't know. Heard better detergents in the 89 so am gonna stick with it for awhile, although 40 cents a gallon cheaper hurts. Why the disparity between the two? Used to be about 10 cents if I remember correctly.

 

[ram1500rsm]

i run 91 on mine and that's as high as octane will go here in Venefornia.

 

[kurek]

Why the disparity between the two? Used to be about 10 cents if I remember correctly.

I think the word you're looking for is inflation. Loaf of bread used to be 59 cents too

 

[smiley]

Octane isn't mileage. It's anti-knock. think "smooth explosion vs. two firecrackers tied together. I get clattering (two firecrackers) on some 87 octane pumps, depending on the blend they happen to get delivered. With 89, I don't. YMMV

Reason this misconception is out there is ethanol is often not in top choice aka premium. So people get better gas mileage and think octane was the reason. My Ram didn’t seem to like 87 just lacked the power I was used to maybe it was in my head but always preferred 89 especially with no ethanol.

 

[kurek]

Ethanol has unfortunately become highly political, which is why it's impossible to have a rational conversation about it.

The chemical compound C2H5OH has an effective "octane" of 113 and burns extremely cleanly - plus it brings oxygen into the combustion chamber in the liquid fuel and that oxygen is available to the combustion process so when a gallon of liquid fuel consisting of 15% CnH2n+2 and 85% C2H5OH is burned, it is approximately equivalent to burning 3 quarts of C8H18 while also pumping in an additional 145 cubic feet of air worth of oxygen that doesn't have to get pulled past the intake/valves and doesn't carry 115 cubic feet of inert nitrogen with it, doesn't have to push all that heavy useless nitrogen out through the exhaust either.

The same effect occurs on a smaller scale with smaller blend %'s, in any case you're supplementing the anaerobic alkenes with a clean high "octane" behaving oxygenator and the result is cleaner and more energetic combustion.

I convert every vehicle I own to run E85 (well locally in AZ it's E54 because of heat/elevation) and will be converting my Ram to burn that as well the minute it's out of warranty. In my book fuel ethanol's a very good thing.


On the topic of gasoline I generally run premium E10 in my Ram, around home always from the same 2 stations because it's convenient to my house & office. On the road sometimes I've run 87 and even 85 in Utah once but it's harder to notice small changes in power while on a road trip, they could just as well be attributed to changes in elevation or unfamiliar grades.

The only big fuel-related change I ever experienced in the Ram was when I filled (with premium) at a specific station I don't usually visit and the truck became noticeably sluggish a few minutes later, stayed that way until I had burned half the tank and topped up at my usual station again.

 

[seabrook]

I'd hazard a guess the majority of trucks are filled up with 87,lol. I run 87 in my wifes 2016 5.7 Challenger which is the same as the trucks,89 reconmemded but 87 acceptable.Car runs the exact same numbers at the track on 87 as it does on 89,and actually slows down if I fill it up with 94.It also gets better milege on 87,as 87 is cleaner fuel.The additives added to increase octane numbers,don't burn worth ****,and will slow the combustion chamber burn down.I had an uncle who was a chemist with Mohawk for years,and he used to describe high octane fuel as "dirty" fuel because the additives don't burn all that great compared to gasoline

Hey man that’s complete crap about the dirty fuel I work for a large refiner. Also you are talking ALKYLATION ( liq GOLD)with with some big variables S or HF now some non HF also how about a ismoam mix for a boost or stinky butane spike. They all burn perfectly down to a silence... kengine

 

[seabrook]

Ethanol has unfortunately become highly political, which is why it's impossible to have a rational conversation about it.

The chemical compound C2H5OH has an effective "octane" of 113 and burns extremely cleanly - plus it brings oxygen into the combustion chamber in the liquid fuel and that oxygen is available to the combustion process so when a gallon of liquid fuel consisting of 15% CnH2n+2 and 85% C2H5OH is burned, it is approximately equivalent to burning 3 quarts of C8H18 while also pumping in an additional 145 cubic feet of air worth of oxygen that doesn't have to get pulled past the intake/valves and doesn't carry 115 cubic feet of inert nitrogen with it, doesn't have to push all that heavy useless nitrogen out through the exhaust either.

The same effect occurs on a smaller scale with smaller blend %'s, in any case you're supplementing the anaerobic alkenes with a clean high "octane" behaving oxygenator and the result is cleaner and more energetic combustion.

I convert every vehicle I own to run E85 (well locally in AZ it's E54 because of heat/elevation) and will be converting my Ram to burn that as well the minute it's out of warranty. In my book fuel ethanol's a very good thing.


On the topic of gasoline I generally run premium E10 in my Ram, around home always from the same 2 stations because it's convenient to my house & office. On the road sometimes I've run 87 and even 85 in Utah once but it's harder to notice small changes in power while on a road trip, they could just as well be attributed to changes in elevation or unfamiliar grades.

The only big fuel-related change I ever experienced in the Ram was when I filled (with premium) at a specific station I don't usually visit and the truck became noticeably sluggish a few minutes later, stayed that way until I had burned half the tank and topped up at my usual station again.

Man no kidding e85 is race fuel it would be e100 but everyone would drink it lol just kidding

 

[Wild one]

Hey man that’s complete crap about the dirty fuel I work for a large refiner. Also you are talking ALKYLATION ( liq GOLD)with with some big variables S or HF now some non HF also how about a ismoam mix for a boost or stinky butane spike. They all burn perfectly down to a silence... kengine

They might all burn down to a "silence" as you call it,but they also don't create the same btu's as gas.And I would have to disagree with you on how clean they burn,when I mix 5 gallons of 114 race fuel in with 10 gallons of 94,my plugs are coated in white flaky crap,that carries right out to my tail pipe tips,and you're telling me the chemicals added to slow the flame front down,but leave a white flaky residue all the way out to my tips,is a clean burn,yea don't think so bud.I lean towards trusting what my uncle said about high octane fuel being a dirty fuel,he was a chemist for to many years not to know what he was talking about,lol.BTW what is your position in the refinery?