Mixing low and high octane gas ?

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If you mix low octane gas (say, 87) with higher octane (say, 91 or 93), do you get the average, or something else ?

I ask because I can get 87 through my employer, but my car doesn't run well on it under load. If I mix it with 91 or better at personal expense there is a definite improvement.
I have heard that gas stations only really have Regular and Super in their storage tanks, and they are mixed at the pump for the Mid-Grades. I don't know if that's true, but if it is I'd like to know how to optimize it.
 
It is true that some gas stations (the majority around here) only have 2 tanks and blend at the dispenser, so yes, you can blend your own and get mid-grade.
 
Originally Posted By: milkboy


I have heard that gas stations only really have Regular and Super in their storage tanks, and they are mixed at the pump for the Mid-Grades. I don't know if that's true, but if it is I'd like to know how to optimize it.



as some one who's worked @ a couple gas stations off& on, Yes, that is 100% correct..
dunno about "optimizing" though...
 
Are you stealing gas from your employer?
smile.gif
 
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go to Indiana, you can buy your choice of 87, 89, 90, 91, or 92 at some stations on Washington St in Indianapolis.

Still never did figure out how to tell if your engine "needs" higher octane, as the eternal debate of things like "Is 87 OK in a Mercedes-Benz S600" etc etc rages on..

What about small-block Chevy and its variants?
 
Originally Posted By: TechnoLoGs
go to Indiana, you can buy your choice of 87, 89, 90, 91, or 92 at some stations on Washington St in Indianapolis.



LOL, I manage a Goodyear store off W Washington St. ! And yes I agree , previously I only used to see 93 octane whenever I would fill up. The other day, filled up at Phillips 66 ( toptier and all, ya know ) and 92 octane! My car doesnt run any differently though, and the mileage/power hasnt been affected.
 
Yes. However in your situation it might be cheaper to mix 90% regular and 10% toluene. If you could find some 100 octane unleaded racing fuel somewhere for $5.25/gal this could also work in your favor. Can I ask what your line of work is?

edit, wait, is this 87 thru your employer free or just cheaper than retail?

To make it even more interesting if you were allowed leaded fuel a little leaded would go a long way to boosting your octane, in a non-linear (in a good way) fashion, but that's more complicated and less legal than you need to know.
laugh.gif
 
Employer will reimburse travel expenses including fuel, Regular-grade only.

Tech - here's my over-simplified method for determining octane requirements :
1 - If there are any symptoms of detonation (knock, ping) or lack of power when
2 - Accelerating at a normal rate to a normal passing speed, while
3 - The engine is under load from extra weight, or up a mild grade,
Then that engine requires a higher grade of gasoline IMO.
 
Can you get E85? Can you get regular without Ethanol? Buy your own E85, a gallon or two per tank, on top of regular 100% 87.
 
Originally Posted By: eljefino
Can you get E85? Can you get regular without Ethanol? Buy your own E85, a gallon or two per tank, on top of regular 100% 87.


All the gas around here is 10% ethanol, as far as I know.
 
Why not go through the receipts in the trash and find some for 87 octane? Just find some that are close to what you spent on high test and submit them. Sometimes you even find receipts stuck in the pump.
 
I've also heard if your car requires 93 octane to avoid pumps that have only one nozzle because you may end up getting a gallon or two of 87 if that was the last purchase before you start receiving 93. I don't know how true that is.

I know they are hard to avoid. Usually BP stations have three separate nozzles. I have a couple of cars I've turbocharged and have always ran 93 but can't say I've ever had any issues buying 93 from these single nozzle pumps. But who knows they could get by with 87. I have never tried 87 in them just as a precaution.

I used to run 93 in my 68 Ford 302 because I thought leaded fuel sold back in the day was around 93 octane. One day I tried 89 just to see if I could get by with it and the engine pinged horribly. Turned out the static timing was advanced 10 degree!. I set the static timing to factory settings and all was fine. Further investigation shows that leaded fuel sold around 1968 was around 89 octane and the engine has an 8:1 compression ratio. So there was no need to run 93 in it to begin with.
 
Originally Posted By: eljefino
Why not go through the receipts in the trash and find some for 87 octane? Just find some that are close to what you spent on high test and submit them. Sometimes you even find receipts stuck in the pump.

sneaky :))
BUT EFFECTIVE!
 
Originally Posted By: surfstar
It is true that some gas stations (the majority around here) only have 2 tanks and blend at the dispenser, so yes, you can blend your own and get mid-grade.

89 is 66% 87 octane & 334% 93 octane
 
Originally Posted By: KeithS_NW_Ohio
Originally Posted By: surfstar
It is true that some gas stations (the majority around here) only have 2 tanks and blend at the dispenser, so yes, you can blend your own and get mid-grade.

89 is 66% 87 octane & 334% 93 octane


That means that it's exactly proportional, so 50% 87 + 50% 93 should equal 90 octane.

Good to know !
smile.gif
 
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Yes, it is true, many gas stations hold only regular and premium in inventory, and the pumps blend them on the fly to obtain mid-grade.

But sometimes, if the station has 3 tanks but uses (usually older) pumps that can't mix on the fly, the delivery driver will blend regular and premium fuel off the truck into the mid-grade storage tank.

I've heard that the relationship between gallons of regular and gallons of premium vs. net octane rating isn't exactly linear (50% 87 octane and 50% 93 octane may actually get you 89.5 or 90.5 octane, for example, but not exactly 90 octane)... but it is very close.
 
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