Ever put 87 octane in an X with a supercharger??

[GrumpyOldMan]

....well I had a major BRAIN FART the other day and did just that - I pumped 6.5 gallons of 87 into my truck and about DIED!!

:thumbdown:


I was in a panic about how much I had to baby it and asked gadget about it...well I ALSO did some reading online and found the following page that tells you how to calculate the resulting octane of your fuel mix which is AWESOME to know!!

http://www.racegas.com/article/52


Anyway, I did the math on my boo boo and found this (excerpt below):

Then, use this equation to find your octane:

( [ % Fuel A ] x [ Octane of Fuel A ] ) + ( [ % Fuel B ] x [ Octane of Fuel B ] ) = Octane of Mixture​

so in my case that is :

21 gallons total, 6.5 of 87 in it means:

6.5 gal @ 87 (6.5 / 21 = 0.3095 or 31%)
14.5 gal @ 93 (14.5 / 21 = 0.69 or 69%)

so substituting we get

( 0.31 x 87 ) + ( 0.69 x 93 )

26.97 + 64.17 = 91.14 Octane

HURRAY!!! I still have a tank full of 91 octane so boosting SHOULD be safe on the tune Gadget gave me (I'm sure he'll chime in tonite if it's not) HOWEVER I intend to drive like a Prius owner down to that station and top it off with 100 octane which means maybe 2 gallons by the time I get there....JUST TO BE SAFE!!

the BONUS is that I now know where I can routinely lighten my wallet for a tank FULL of 100 octane should I want it (not till I get a beefed bottom-end and a tune that will use it!)


IN CONCLUSION.... if ya ever screw up like I did, just do the math and see if you are okay!!


Dave - a relieved boosted X-runner owner

 

[sdxrunner619]

I filled up with a full tank of 87 because I was at a turn off, light on, and nearest station was another 100miles away. They had no 91/93 . Put in 10 gallons of 87. Stay out of boost, light throttle and you will be fine. The whole point of higher octane fuel is prevent spark knock, which is a by product of high combustion temps, i.e hi compression race engines, or forced induction. Our engines can adjust spark timing by a rather large degree, and the computer can and will adjust for different octanes.

Knock will usually happen under high load, not partial throttle conditions. So if you do it, just drive it easy and keep diluting it with more high test.

 

[ntinhri]

I wouldnt worry about it.. just stay outta full boost and no 1/4 mile racing.

 

[justin13703]

Ive done it before and it never bothered me. I don't run the piss out of mine so I didn't have anything to worry about. Ive also brain farted and pumped 93 into my old Cherokee just out of habit. I think that bothered me more than putting 87 in my truck lol