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Mixed 87 and 93 to get better deal what math to use?

YY1

YY1

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By my rough calculations, mixing equal parts 87 octane @ $3.52 and 93 @ $3.82 should yeild 90 octane @ $3.67 which is a better deal than the mid grade 89 octane sold at $3.72.

Am I crazy?

Today I got 8.5 gal of 87 and 8.2 gal of 93.

Any math guru care to give me a formula to find my true octane rating and cost per gallon?
 
So you go to the gas station with multiple containers, you fill them up with different octanes, you take them home and mix them yourself to save money? Gotta say, my time is worth way more than going to all that effort to save a few bucks. Your above calculations save you $.05 a gallon, so 20 gallons would save you a dollar total.

Yeah, you're crazy. :)
 
Only thing I do is cut racing gas with 93 octane to save some cash
 
No, I swipe the card, dispense the 93 into the car, put the nozzle back, swipe again, and dispense the 87.

Takes less than 45 seconds additional time.

I get 90 for less than the price of 89.

Around here 89 is 20 cents more than 87. My car knocks on 87, but not on 89.
I'm pissed theres a 20 cent diff for 2 points octane, while there's only a 10 cent difference betwen 89 and 93 (a 4 point increase), but to run 93, which I don't really need would be a 30 cent increase per gallon.

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It cost me $75 to put 3/4 tank of 89 in the other day.

If I can get a better octane rating for less money for the "price" of 45 seconds, I call that a bargain.

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Even at $5 a month, thats $60 a year, and that's almost a free tank of gas every year :):)
 
Well, if you put it like that, then you're a mad genius. My trusty 'ol 318 2bbl doesn't knock on 87, but it's about as fast as a granny pushing a walker, so there's a tradeoff. :)
 
How do you know what you've got? Do you carry a horde of oil company chemists with you wherever you go? Seems like a lot of trouble for a questionable result.
 
I'm going to have to trust the State cert stickers and the R+M/2 method on octane rating, and...

I know starting with the 93 will at least guarantee that the first "hose full" of the 87 will be 93, to counter the first hose full of 93, which is probably 87 ! (where's the upside down exclamaition point?)

Again, 5 cents per gallon cheaper (some folks drive across the street for that), and 1 point higher octane, for the cost of swiping the card twice, punching a few buttons twice, and hanging the nozzle up twice.

Because the price difference versus the value add is so disproportionate, it's theoretically possible (if we had that math formula) to get 91 or 92 for a lot less than the 93 (maybe even less than 89), depending on how much of each you used.

I know some 7-elevens have 87/88/89/91/93, but there's none on any of my normal routes.
(and I haven't checked those to see what % you get for the added prices)

I'll accept the title "mad genius"....and I JUST cut my "Reverend Jim" hairdo this past weekend (it was turning into a "David Lee Roth" [is that a combover?] hairdo)
 
YY1 there's absolutely nothing wrong with doing a blend of lower & higher octane fuels, to save a few bucks & I'm sure there is a octane formula on google somewhere, who cares, what the octane is, if it works & you saved a few $$$$ in the process...

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maybe if it's 87 & 93 {87 + 93 = 180 dived by 2 = 90} 50% of each it's just 90 octane, maybe simple as that, but I doubt it....
 
Yeah, I got that part, if it's EQUAL ammounts, but based on the 20 cents for 2 points versus the 10 cents for 4 points, the "back of my mind" says you can get 92 for less than (or the same as, or just slightly more than) the cost of 89!

It's like the 2 liters of Pepsi that are $1.89, when the 1.5 liters are 99 cents.
Buying the two 1.5 liters gets you that 3rd liter (or 33% more)...for 9 cents.
(...and it doesn't go flat as fast!
 
Yeah, I even used to do it with beer.

Back when you could get Bud in 8oz, 12oz, 16oz, 32oz, and 40oz, and six packs (8, 12 and 16), 8 packs (8), 12 packs, 24 packs, etc.

I'd calculate the maximum ounces I could get for the money I had, using various combinations.
Sometimes mixing it up yeilded a few free beers, and that my friends, is REAL value!
 
pabster said:
Well, if you put it like that, then you're a mad genius.
Click to expand...


doc+brown+thinking+cap+back+to+the+future.jpg
 
You should have seen the looks on some of the storekeeper's faces when a teenager walks in, stares at the cooler for about 5 min, and then buys one case, one 12 pack, a six pack of tall boys, two 40s and one quart!
 
YY1, now you're talking! I'm a big fan of beer, but I have never calculated different sizes and prices to determine the perfect formula for the most beer for the least amount of money.

If we ever meet, I'm buying you a beer. And when I say beer, I mean one tall boy, one 40, a six pack, and a brick of 30 PBR's.
 
I have a formula in Excel that I picked up somewhere. I'd be happy to share it here but don't know how to upload or post an Excel spreadsheet. It does confirm a 50/50 blend of 93 and 87 octanes comes out to 90 octane.
 
Went to see Southern Culture On The Skids a few months ago, and the house beer was PBR.

After a draft Stella, I must have had 10 or 12 of those dang $1 PBR's

You know, now that I think about it I think I had a Stella about every 4th beer.

Now I'm even averaging the actual drinking!
 
My car doesn't mind 91 if I'm just cruisin around, but 93 is usually only a few cents more. If I've been running 93 sometimes I'll throw in $20-$30 of 87.
 
The basic formula to average something is add up the numbers and divide by how many numbers. I.E. 93+87=180. Divide 180 by 2=90.

If you have unequal parts then follow this example: Out of 20 gals total 5 gals is 110 and represents 25% of the total tank. Take the 110 octane number and multiply by .25. Do the same with the 91 octane number. You get 27.5 and 22.75 respectively. Now just add three parts of 91 (22.75 x 3 or 91 x.75) and one part of 110 (110x.25) and get your final octane number. Octane result = 95.75 = (91x.75)+27.5
 
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