How to blend 91 Octane in 87/89/93 Octane pump

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Originally Posted By: pacem
The problem with that is there are vast areas that don't have higher than 91 Octane, CA or AZ being prime examples, or Nebraska. Plus some mountain states where "Regular" is 85 Octane. Then I would have to reflash my PCM. What happens if your PCM person is unavailable? DIY?
What vehicle/engine are we talking about here? Just have the computer tuned to 91. I don't see how running 93 in it would hurt anything.
 

pacem

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I think I am going to bite the bullet here and do the 93 Octane tune... I have a spare PCM I can tune for 91 or 89 or whatever.
 

pacem

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Originally Posted By: Quattro Pete
What vehicle/engine are we talking about here? Just have the computer tuned to 91. I don't see how running 93 in it would hurt anything.
96 Roadmaster with LT1, ported heads, cam, etc. etc. It needs at least 91 Octane to run well. Now I have had it tuned for 87 and that's fine but I rely on KC to detune in, retard timing, which I would rather not. with 87 it runs "OK" but loses power and loses mpg compared to higher octane tunes. I use PCMForLess.com, they do great job.
 
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How is this PCM being tuned? Via a removable chip or the diagnostic port? If it's just a chip your tuner can make you one where the spark maps have been retarded a few degrees that you could just pop in when necessary.
 
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Originally Posted By: Quattro Pete
Originally Posted By: pacem
It's not that it would cost more but that it wouldn't do anything,
Sure it would. It would save you the trouble of having to blend two types of gasoline. Personally, I'd just run 93 and not worry about it.
thumbsup
 
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Originally Posted By: CivicFan
I used to alternate 93 and 89 with a quarter of a tank at a time. But filling up every other day and remembering which car had what gas in it previously got burdensome very quickly. Now I pump 93 only.
93 for the Civic? Is it the Si? If not, those engines are designed to run efficiently on 87. Waste of money IMO.
 
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Just run the 93. It is best for bunches of reasons. Really. BTW, the initial additive amounts do more octane raising than the same amount with a high octane to start with. The results diminish. So simply using algebra is close, but not really right. Use the 93. No harm and a very smart thing to do with a tune. You tune means it needs at LEAST 91. Use 93 and forget about it. Use 93.
 
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Get a gas rewards credit card, I have a citi/citgo but everyone makes them. With 4% cash back I could almost go up a grade and have it pay for itself. I would buy almost a tank of 93 in your situation then top it off with a couple gallons of 87. This will ensure the high test gas in your hose that you paid for winds up in your tank and you leave something cheap for the next guy. You are also assured that if you get some stale 93 from not selling as fast you have the volatitle 87, important in some seasons. The tanker drops 87 and 93 anyway and the pump mixes it... unless your 89 is the only E10 like the corn states sell it.
 
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