Who says 91 octane is not needed?

[Slip Kid]

Around here most places have 87 which sometimes has ethanol, 89 which always has ethanol, and 91 that has none.

With my 93 motor (ala Renix) I get better mileage on the 89 than on the 87, yet I have never calculated with 91 as I have rarely gotten it. The 89 being better than 87 was also reported by my father who previously ran the same motor in it's original 1993 configuration. I continue to get the 89 most of the time, as it's also cheaper at the place I go to buy. I do not have the Renix knock sensor installed which may have something to do with it having the same results as it did on OBDI. My results don't make sense, but the OPs do, as, at least around where I am, premium is usually alcohol free.

 

[bigalpha]

Young whipper-snappers!

Norwalk, Hancock, and Gulf service stations, 1961-1975 family business.

Excluding diesel, two tanks--one regular, one premium. Blend pumps--you could move the selector from straight regular to straight premium and about FIVE mixes between the two.

Old tech rules!

A man of many talents.

Interesting stuff there alpha, I'll have to pay a little more attention to the covers- normally I just hear the 'thunk CLANK' when I run over them.

96XJ, I think your corn bin exploded.

Yeah, it's my job. Usually pretty boring but comes in handy in times like this. 96JX and Joe look like they have experience with this stuff too.

I didn't have any handy pics showing all of the lids for the ports, but once you see them all, it'll make perfect sense.

 

[iwannadie]

I'm gonna give 91 a shot and see what my miles per gallon do in response. The cost is no big deal, I just always assumed this old tractor motor lived on 87 and had no need for 91.

I drive the same route basically every day and no freeway driving at all so I figure 2 months(about 9 tanks) should give me a good idea if I gained anything.

Right now I get 16.6-16.9 mpg for the past few years according to the on board computer, I'd like to see 17's or even 18 ha.

 

[JNickel101]

Everyone keeps talking about 87, 89 and 91....around here you can (will) find 86, 88 and 90....some places have 91....

I miss PA where you had 87, 89 and 93...and sometimes 94 at the Sunoco stations....

Why such the huge disparity in octanes?

 

[thechief86]

i dunno.... here in tn 93 is readily available....

 

[88 Wagonman]

Everyone keeps talking about 87, 89 and 91....around here you can (will) find 86, 88 and 90....some places have 91....

I miss PA where you had 87, 89 and 93...and sometimes 94 at the Sunoco stations....

Why such the huge disparity in octanes?

Before ethanol in Boise, ID 90 or 91 was the highest you would see, now it's 93 because the ethanol raises the AKI.

 

[96XJ_4.0]

279 miles on 87...

Fillup with 91 - 15.6 gallons

 

[96XJ_4.0]

295 on 91 octane (and I did 20+ miles of off roading!

fillup 15.1 of 87


So if this one is under 290 then I'm sticking with 91+ octane.

 

[old_man]

Different altitudes require different octane, hence the low numbers here in Colorado. The biggest reason most people see a difference in mileage with a higher octane is that the higher octane tends to have a higher detergent ratio, cleaning the injectors.

I sold commercial fuel suppliments and additives for several years. I didn't read everything in this thread, but higher octane does not mean higher energy. Octane is a measure of the anti knock properties of the fuel.

If you really want to help your mileage on an older rig, run a can of BG44k in the fuel to clean out the injectors and carbon. I run a can every 10k in every vehicle I own. Don't bother with the low cost crap, because that is exactly what it is, crap.

 

[winkosmosis]

I had 1/2 tank 87, filled the rest with 93, for an avg of 90. At the next fillup, I calculated 18.5mpg instead of the usually 17. BUT, this was at a different gas station, because I was about to run out. I'll go to the original gas station and do an early fill up, then add the two miles and gallon numbers together for the real mpg.