Mixing 89 and 93 oct fuel - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

cmore · 03-14-2011, 02:36 PM

If u mix 5 gal of 89 oct and 5 of 93, do u get 10 gal of 91?

supersport24 · 03-14-2011, 02:53 PM

I'm not real sure! I usually add around 3 gallons of 116 on top of 91. It'd be interesting what mixing octanes computes out to.

mpiper · 03-14-2011, 03:01 PM

Gas stations only have 2 tanks! They have regular and they have premium. The mid grade is made by setting a ratio and pumping from both.

So, yes, you can do exactly what they do. But remember the ratio's may be off if you don't add exactly the same. But a ballpark should be close enough.

No magic numbers, Simple average. 5 gallons (87) + 5 gallons (91) = 10 gallons 89 (gas station mid grade)
So, 5 gallons (89) + 5 gallons (93) =10 gallons (93+89/2) = 10 gallons (91)

The Stig · 03-14-2011, 03:05 PM

Mixing different octanes won't do any harm to the computer or to the car. To answer your question, yes. If you mix 5 gallons of 89 and 5 of 93 you will get 10 at 91. It's simple solution mixing. Because the camaro's BCM doesn't recalculate timing every time a new tank is put in, most likely nothing will happen. To get a benifit of adding the 116 ontop of 91 you would need to do a fuse pull with the new gas in so the car learns the fuel.

cmore · 03-14-2011, 05:40 PM

The reason I asked is that 91 is recommend but we have 87, 89 and 93 avail. So not sure I gain anything running 93. Might want to mix 89 and 93 with the heaver proration being 93.

Russell James · 03-14-2011, 05:52 PM

Just put the 93 in.

D Day Dog · 03-25-2011, 05:11 PM

I can't get above 90 at any pump in Alaska unless I buy 104 from a local place that sells racing gas. To confirm then, if I mix say: 9 gal. of 90 and 9 gal. of 104... I get 97? So it's as easy as taking the two equal amounts of gas with different octane - add the octane numbers together - and dividing them by 2 to get an average? If so, sweet.

mpiper · 03-25-2011, 05:47 PM

D Day,
That's exactly it. If the amounts of gas are equal, just divide by two. In fact, look at the octane rating sticker on your gas pumps. The way the octane is calculated is RM+TM/2 Which is Research Method + Test Method (not real name, I forget it right now) divided by 2. It's simple math. I work for an oil refining company and we only produce 2 levels of automotive fuel. If a gas station has 3 tanks, they mix the two to get the third, then pump it into the tank.

It only gets hard if you have uneven amounts of gas. but even then, the formula is simply this:

(G1*O1)+(G2*O2)/(G1+G2)

G1 = Gas1, G2 = Gas2, O1 = Octane of Gas1, O2 = Octane of Gas2.

Example: 4 gallons 89 octane and 10 gallons 93 octane
(4*89)+(10*93)/(4+10) => 356+930/14 => 1286/14 =>91.86 octane

The reason you don't divide by two is the uneven amounts of gas force you to factor in the percentage, while even amounts allow you to do the math for 1 gallon of each just to be lazy.

D Day Dog · 03-25-2011, 05:55 PM

Quote:

Originally Posted by mpiper

D Day,
That's exactly it. If the amounts of gas are equal, just divide by two. In fact, look at the octane rating sticker on your gas pumps. The way the octane is calculated is RM+TM/2 Which is Research Method + Test Method (not real name, I forget it right now) divided by 2. It's simple math. I work for an oil refining company and we only produce 2 levels of automotive fuel. If a gas station has 3 tanks, they mix the two to get the third, then pump it into the tank.

It only gets hard if you have uneven amounts of gas. but even then, the formula is simply this:

(G1*O1)+(G2*O2)/(G1+G2)

G1 = Gas1, G2 = Gas2, O1 = Octane of Gas1, O2 = Octane of Gas2.

Example: 4 gallons 89 octane and 10 gallons 93 octane
(4*89)+(10*93)/(4+10) => 356+930/14 => 1286/14 =>91.86 octane

The reason you don't divide by two is the uneven amounts of gas force you to factor in the percentage, while even amounts allow you to do the math for 1 gallon of each just to be lazy.

Piper: you rock, dude. I was just looking to see if someone placed an example of an uneven formula here - math is NOT my strongpoint.

I'd like to save some costs when I fuel up and 1/2 a tank of 90 mixed with 1/2 a tank of 104 (at $10.25 a gal.) is EXPENSIVE, just to have easy math.

Thanks again, bro !

Dog

djm96z28 · 03-25-2011, 07:08 PM

Quote:

Originally Posted by cmore

The reason I asked is that 91 is recommend but we have 87, 89 and 93 avail. So not sure I gain anything running 93. Might want to mix 89 and 93 with the heaver proration being 93.

Just an FYI, I've been doing that with my LT1 for 15 years. Saves a little cash and 91 octane is considered premium gasoline. I fill up with premium, then at half a tank I fill with 89. Then next time premium..... I do write it down to keep track.

Hotrod6464 · 03-25-2011, 07:36 PM

I put 5gal gal of 110 and then fill up with 93

cmore · 03-25-2011, 07:44 PM

If the car is designed to run on 91 why bother with 110 and even 93?

03-14-2011, 02:36 PM	#1
cmore Drives: 2011 Victory Red Auto 2SS Join Date: Aug 2010 Location: West Tn Posts: 628	Mixing 89 and 93 oct fuel If u mix 5 gal of 89 oct and 5 of 93, do u get 10 gal of 91?

03-14-2011, 03:05 PM	#4
The Stig knows 2 facts about ducks Drives: ...and they're both wrong Join Date: Aug 2009 Location: The HMS Invincible Posts: 25,072 View My Garage	Mixing different octanes won't do any harm to the computer or to the car. To answer your question, yes. If you mix 5 gallons of 89 and 5 of 93 you will get 10 at 91. It's simple solution mixing. Because the camaro's BCM doesn't recalculate timing every time a new tank is put in, most likely nothing will happen. To get a benifit of adding the 116 ontop of 91 you would need to do a fuse pull with the new gas in so the car learns the fuel. __________________

03-25-2011, 05:47 PM	#8
mpiper Drives: 2011 Black 1LT RS Join Date: May 2010 Location: Texas Posts: 496	D Day, That's exactly it. If the amounts of gas are equal, just divide by two. In fact, look at the octane rating sticker on your gas pumps. The way the octane is calculated is RM+TM/2 Which is Research Method + Test Method (not real name, I forget it right now) divided by 2. It's simple math. I work for an oil refining company and we only produce 2 levels of automotive fuel. If a gas station has 3 tanks, they mix the two to get the third, then pump it into the tank. It only gets hard if you have uneven amounts of gas. but even then, the formula is simply this: (G1O1)+(G2O2)/(G1+G2) G1 = Gas1, G2 = Gas2, O1 = Octane of Gas1, O2 = Octane of Gas2. Example: 4 gallons 89 octane and 10 gallons 93 octane (489)+(1093)/(4+10) => 356+930/14 => 1286/14 =>91.86 octane The reason you don't divide by two is the uneven amounts of gas force you to factor in the percentage, while even amounts allow you to do the math for 1 gallon of each just to be lazy. Last edited by mpiper; 03-25-2011 at 05:49 PM. Reason: Explaining why the 2 disappeared in the formula.

03-14-2011, 02:53 PM	#2
supersport24 Drives: Black 2011 2ss Join Date: Nov 2010 Location: Nebraska Posts: 40	I'm not real sure! I usually add around 3 gallons of 116 on top of 91. It'd be interesting what mixing octanes computes out to.

03-14-2011, 03:01 PM	#3
mpiper Drives: 2011 Black 1LT RS Join Date: May 2010 Location: Texas Posts: 496	Gas stations only have 2 tanks! They have regular and they have premium. The mid grade is made by setting a ratio and pumping from both. So, yes, you can do exactly what they do. But remember the ratio's may be off if you don't add exactly the same. But a ballpark should be close enough. No magic numbers, Simple average. 5 gallons (87) + 5 gallons (91) = 10 gallons 89 (gas station mid grade) So, 5 gallons (89) + 5 gallons (93) =10 gallons (93+89/2) = 10 gallons (91)

03-14-2011, 05:40 PM	#5
cmore Drives: 2011 Victory Red Auto 2SS Join Date: Aug 2010 Location: West Tn Posts: 628	The reason I asked is that 91 is recommend but we have 87, 89 and 93 avail. So not sure I gain anything running 93. Might want to mix 89 and 93 with the heaver proration being 93.

03-14-2011, 05:52 PM	#6
Russell James Drives: '15 SS 1LE, '69 Z28 drag car Join Date: Dec 2009 Location: Mich Posts: 4,482	Just put the 93 in.

03-25-2011, 05:11 PM	#7
D Day Dog Drives: 2011 1SS Imperial Blue Metallic Join Date: Feb 2011 Location: Alaska Posts: 482 View My Garage	I can't get above 90 at any pump in Alaska unless I buy 104 from a local place that sells racing gas. To confirm then, if I mix say: 9 gal. of 90 and 9 gal. of 104... I get 97? So it's as easy as taking the two equal amounts of gas with different octane - add the octane numbers together - and dividing them by 2 to get an average? If so, sweet.

03-25-2011, 07:36 PM	#11
Hotrod6464 Drives: 2011 Black 2SS/RS LS3 M6 Join Date: Aug 2010 Location: Titusville,PA Posts: 129 View My Garage	I put 5gal gal of 110 and then fill up with 93

03-25-2011, 07:44 PM	#12
cmore Drives: 2011 Victory Red Auto 2SS Join Date: Aug 2010 Location: West Tn Posts: 628	If the car is designed to run on 91 why bother with 110 and even 93?