03'55AMG

I just found a gas station about 2 miles from me that sells 110 octane Racing gas. I immediately read through the '110 octane question' thread, and discovered that the cars Stock (me) ECU can only time up to 95 octane on its own without a tune, which then requires mixing 91 or whatever gas you have available and 110. how ever, I believe the 110 IS leaded, which I know will eat up the cats/o2's.. but how much 110 would i actually have to run to actually yield my cats/o2s worthless? and if i were to have 12 gallons of premium (93 octane), how much 110 octane would i have to mix in with the 93 to equal 95 octane? Sorry for the very newbie questions, and FWIW, is $5.99/gallon a good price for 110 oct.?

mikey33

That is a cheap price, and you just need to do the math to get your average at 95.

alextaylor29

Yeah that's a smoking price! I buy 109 Octane here for $10.99 a gallon. I usually put in 2 gallons of 109 mixing with my 91 (The highest available in AZ) and run with that.

You can DEFINITELY feel the performance increase. I read some where that with our 500 HP cars, you'll get an extra 30-50 HP when you put in race gas.

I do it once a month just to have fun on my commute (100 miles daily) and I love it. Also it's a hidden/slight advantage if you choose to race somebody on the streets.

Totally worth it and I'd just go with a couple of 109 octane gallons per tank.

infantry

Hey speaking of that! where do you buy your 109 octane at in AZ?

I would do at least 3/4 premium and fill the rest with 110.

mikey33

From what I am told you are supposed to do a 4/1 ratio. 4 gallons of premium to 1 gallon of high octane. FWIW that is what I do if I ever get the expensive stuff

AKnight55

So you guys really think that on a stock car running 95 is noticeable over 91?

Nstar

Depends on what you're doing and I don't know about 95 which seems like overkill when stock, but the car seems smoother when using good ol' east coast 93 than the trash they serve out west. I really don't understand the omission of 93 and it irks me whenever I'm out here.

AMG_RL

this is a good reference point although it's for 100oct. without a tune anything above 95oct is pretty pointless. My STi showed no gains w/o a tune above 94oct, only after tuning for 107oct did I see some monster numbers

03'55AMG

Sweet! next time i fill up I'll put in a 5/1 (5 gallons 91 to 1 gallon of 110) but IF the 110 IS leaded, is that much going to hurt anything? i wont do it every fill up, just when i want to mess around a little.. and im only talking maybe 3 gallons of 110 a tank like every two months? in a month i use about 40-45 gallons of 91/93 (w/e is available) so a measly 3 gallons of leaded wouldnt harm anything right?

iAMGod

Where did you get your information regarding any fuel containing over 95 octane will require a tune - In Australia we have 98 octane as our premium fuel and some places even retail 100 octane - I was some what confused when I discovered your premium fuel in North America is 94?

To those asking whether there is a difference between 95 and 91 - I noticed a huge difference between 94 and 98 and 100 compared to 94 is like night and day.

TMC M5

Not quite. Here in the U.S. we use the AKI (Anti-Knock Index) to rate the octane of our pump gas. The AKI takes an average of the RON (Research Octane Number) and the MON (Motor Octane Number). That is why you see on the chart provided in this thread a reference to: (R + M)/2.

So a 93 AKI octane gas here in the U.S. is roughly 98 RON: (98 RON + 88 MON)/2 = 93 AKI.

Tom

iAMGod

I see - I had no idea, thanks for the clarification.

AMG_RL

as long as you burn most of it quickly it shouldnt be an issue, my old suby tuner was stated that leaded fuel that was left to sit for a prolonged period of time would cause corrosion issues.

over 95oct. would not require a tune, it just would not be optimal. there is a slight benefit with higher octane fuel but without a tune your throwing your money away on expensive gas.


I can't speak for anywhere else, but CA premium gas is a mere 91oct. Ive had 4 highly modified cars (1972 3tc turbo Carina, gt35r'ed STi, gt35r'ed EVOXI, and c5 z06) and through road tunes and datalogging all have had the similar turn outs. yes there is a slight jump in performance and a reduction in knock if applicable, but after a tune is where the REAL benefits of higher octane are and as such you could justify running premium higher octane fuel.

BTW if anyone's interested, when My Subaru was running on e85 I was putting down similar numbers as 105oct fuel....e85 is only $2.79 a gallon at the chevron down the street from my house

Nstar

I've only been reading this site about 6 months and that's about the tenth time I've seen that someone has had to explain this. You are a very patient man, Tom, and it's good to see civil exchanges on the internet. Kudos.

alextaylor29

In AZ I buy mine at dynocomp (dynocomp.com.) They usually have a few barrels of the stuff, so just show up buy a few gallons and they'll put it in your car right there.

Or bring your own gas can to take it with you.

In my car I could definitely fee the difference and I'm tuned for 91 Octane. This is not scientific but rather just the seat of the pants sort of thing.

Can't wait to get on my headers, a tune, then 109!

BAM!

Hotrod-Realtor

Really???? Chevy Impala, here I come at $2.79 per gallon.

03'55AMG

oh believe me, When i do put in some 110, ill be happy to see 7MPG! lol how long would it take to corrode stuff? it would probably be in the tank for 1-3 days max. and only 1-2 gallons.

TMC M5

No problem.

Thanks! Although, if you ask some people around here..patience usually isn't one of my virtues..

Tom

GHAZAN

C1V1 + C2V2 = C3V3

Concentration 1
Volume 1

Concentration 2
Volume 2

Concentration 3 (resulting octane)
Volume 3 (max capacity of fuel tank)

Math Rules