87 vs 89 Octane
 

Before I get blasted with "Do a search"... I just want to ask you guys if you have ever compared/tried the difference b/t 87 and 89 octane?
I am well aware of the difference in how octane affects combustion, I have an 2003 Z06 w/~11.5:1 SCR, and a 67 BB Camarao with ~13:1 SCR(race gas car)...so I know about compression and octane!!

I have been runnning 87 in my JK, I decided to put 89 in the other week. Well, I got nearly 2 mpg better(calculated by me, not the computer) and the Jeep ran much smoother and seemed to have more power on topend. I ran 2 tanks of 89 with the same results. This week I filled up with 87, gas (according to the computer) is down 1mpg, it does not run nearly as smooth, and seems to stumble more on topend than the previous 2 tanks of 89.

My wifes Lincoln Aviator gets better mileage and runs better on 87, factory says to run 91+. My Jk is the opposite...go figure???:crazyeyes:
I just want to see if anyone else has experienced this? Let me know!!

If you know about octane, then why ask. Octane does not increase gas mileage. Total coincidence. You are compare your calculations to the computer. The computer is not even close. If you do a comparison, you have to everything the same.

I tried the same thing with mine, i ran 4 complete refuels of 89 through it.

The milage changed ever so slightly like yours +1-2 mpg. However i really didnt notice much diffrence in how it ran.

I did the math on the increased milage versus cost, didnt really amout to much; it was actually more cost effective to run the lower octane with less milage per tank than pay the extra to gain a little, but only marginally so. If it had run better, i would have coughed up the extra few cents per gallon, but in my case, it didnt.

I totally agree with IGOFSN that 89 should NOT yield increased mileage, power, etc... and yet, this is at least the 3rd person now who is claiming better mileage with 89 than with 87... Hmmm... :hmm:

I was not agreeing that 89 increased my milage, just that when i did it i noticed a change. Didnt mean to be misleading there, sorry.

What caused it is anyones guess.
Mine would be weather & engine break in.
I could not run both tests simultaneously obviously, so one occured after the other. The 89 one was run second, and therefore in colder weather as winter was approaching, and after the engine had more break in. So my guess on the milage change as stated above at negligible (1-2mpg) was just that, change in climate and more break in time.
I didnt do it to see if i got better milage, i was interested in how it ran. (which I am aware is totally subjective) If it ran better, i would have switched, it didnt by my perceptions, so i didnt switch. That was that.

Actually, I posted in response to IGOFSN, and then saw your post... so that would make you the 4th... except that, as you've explained, you're not claiming that 89 (which resulted in better mileage) gave you better mileage. :crazyeyes:

I still refuse to try this test for myself, because EVERY authority on the subject I've read agrees that an increase in octane will not aid an engine that is not designed to take advantage of that octane...

I will find out for sure, by my calcualtion, how the 87 affects mileage in comparison with 89. Like i mentioned though, according to the computer, it is down by 1 mpg. BTW, my computer has been off by .1 mpg everytime I have calculated miles driven/gallons to fill up.
Driving conditions are the same for both uses, 80% city 20% highway, no AC.

Gofshn...I asked to see if anyone else has experienced this. I did not ask for a tutorial on how ocatane works!!

lmao! wow i really didnt explain myself well at all. i obviously need more coffee before posting.

1. when i took posession of my Jeep i ran 87 Octane exclusively for about 6-8 weeks. milage was right about 16-17 IIRC

2. Switched to 89 and ran 4 tanks through it. Milage ran about 17-18ish

3. Switched BACK to 87 and milage is the same, around 17-18ish. So no net change was really noticed, as i said i think i just hit the curve where the weather had a factor, and the engine was getting more broke in. (And i think i was getting back on the road more then for work, and doing the Holiday runaround to vastly seperated family dwellings)

My main milage is mostly short trips of less than 5 miles, on 45mph roads. Occasionally a longer highway trip where i hit 55-65 for extended periods, which nets me slightly better milage than the around town Stop~n~go.

All that being said, i dont think the change in octane changed my milage one iota, in my less than professional or scientific testing, it was just coincidental.

Thank you - me understoods now. :)

Same topic , diferent car.
With my 04 toyota Sienna van (wish i still had it instead of the jeep).

When we would take trips to laughlin I would use 89 octane because i would get no pinging or knocking while driving throught the hot desert at all with it. The 87 octane would be the opposite.

No real change in mpg though, but a smoother acceleration .