I'm picking up my new 991 next week - can't wait. It will be a daily driver.

I discovered a 76 station between my house and work that sells 100 octane racing fuel for $7.35 per gallon.

I started doing the math:
6000 miles per year (that's how much I drive)
15 mpg = 400 gallons of fuel per year
$3 per gallon difference between 91 octane and 100 octane
= $1200 per year in fuel cost difference between 91 and 100 octane

Not a small number, but not a big number either.

What do you think? What improvement or benefit would I see in using 100 octane rather than 91 octane (if any?). I've never driven with 100 octane before.

 

If you leave the engine stock, it's optimized for about 93/94 octane gas. Anything higher than that will be unrecognized by the engine and is money wasted.

I too live in CA, land of 91 octane. You could mix fuel in every fill up - a few gallons of of 100, rest of the tank at 91 - and get something close to 93 octane. Will you even feel the difference? I doubt it. I tried that a couple of times before DE events, but truthfully it didn't make much difference.

DMoore
'13 C2S
'10 Panamera 4S

 

I agree to mix it and get around 93 octane. Price difference would be even less!

 

I would check as to how the station/blender/refinery is getting the extra octane in the gasoline also. Getting up that high requires either a lot of ethanol, heavy aromatics or alkylate. If it's ethanol I wouldnt use it.

I'm ruling out any lead/av gas

 

^+1 Agree with trysixy. Avoiding ethanol will be far more beneficial than the higher octane gas.

 

Google top tier gas.

 

Add toluene it's cheaper

 

I am thinking getting the gas up to 93 octane is important because both gas metering and spark timing are reduced with 91; thus power and mileage is reduced. I'm not sure if the add-on products will be recognized by the sensors, but it would be interesting to run a couple tanks of 91 and take a 0-100 timing; then run a couple tanks with the additive and take another 0-100 timing.

ChuckJ

 

Don't ask why... but... I've driven a Cayenne (manual) with both 91 and 100 octane. To my disbelief I could certainly feel the difference. However I would not recommend using 100 octane in a 991 or any newer Porsche. That motor is precisely balanced and measured on 93 octane. I would assume prolong use of anything more or less could cause issues.

 

The 100 octane (racing) fuel at 76 gas station doesn't appear to have any alcohol additives...attached online article explains the composition in depth. I'm planning to stop by and fill it up today. Lets see how this car is built to perform

Check this out:
http://www.leesracing.com/fuelspec/g1.html

 

Very interesting. Regarding precise balancing for 91 octane, i'm not sure i believe that. I don't know what the stats are but between LA and Silicon Valley, i would bet a quarter or more 911s sold in the US are sold in California. 91 is all we get. So, either the Porsche is OK to handle it, or it's suboptimal either way (putting in 91 octane or putting in 100 octane).

Mixing is a nice idea but let's be realistic. Am I really going to take the capacity left in the tank, divide it into fifths, swipe my cc, put in one-fifth the capacity of 100 octane, then swipe my card again, and fill four-fifths of 91 octane? All while i'm on a work call on my way to/from the office? I suspect i'll do that twice and then give up.

 

Ok..just did it. 5 gallons of 100 racing and 9 gallons of 91 octane -- to be honest,
I didn't notice much difference -perhaps the rest is crappy 76 gas station 91 octane and I have been filling up 91 v power from shell??? Perhaps i should've filled it all up with 100.......


Edit: came back home...reset my expectations ..drove off after few hours...and YES....there's a difference!!! It's very quick on its feet...in fact the sport felt like sport plus a few time!!!!! From now on I'm doing at least 6 gallons of 100 octane (18 gallons C4S tank) .....it's worth it!!!

 

Mix it to 93. I do it often. you are lucky. Over here, 100 octane is $10!

 

Probably a waste of $$ unless you get a tune too.

 

The Lees Racing 100 octane fuel contains MTBE which is good since it has a blending value of about 130 research octane (worked in refinery for 30 years). Our SDIQ EPA eliminated it from commercial fuel since if the underground tanks leak, the MTBE can be toxic in the groundwater (not that the gasoline or ethanol isnt LOL) .

One issue we found was that MTBE gasoline when blended with gasoline containing Ethanol has a negative blending effect.........5 gals of 100 octane MTBE gasoline blended with 5 gals of 92 Ethanol containing gasoline does NOT give 10 gals of 96 octane gasoline!!!More like 10 gals of 93.5 octane.

So bottom line is get a non ethanol fuel to blend with the MTBE gasoline from Lees Racing!!!