100 Octane - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Ciao · 02-06-2019, 02:23 PM

What can I expect in performance if I pump in 100 Octane (50%/50% 91 Oct) in high altitude (Mile high city in Denver)

AZ986S · 02-06-2019, 03:53 PM

Others may not agree, IMO a waste of money, unless you really need that extra 2 HP with a properly tuned car on the track... others may not agree.

maytag · 02-06-2019, 03:55 PM

Most of the performance gain you'll notice will come from the reduction of weight in your wallet.

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Ciao · 02-06-2019, 04:15 PM

I'm thinking of running 60% 91 Octane and 40% 100 Octane to average 93 Octane which the manual states is the best Octane

maytag · 02-06-2019, 04:32 PM

Quote:

Originally Posted by Ciao

I'm thinking of running 60% 91 Octane and 40% 100 Octane to average 93 Octane which the manual states is the best Octane

Higher altitude you can never find the higher octane stuff like down low. But you don't need it, either. Air density is too low. Use 91. It's appropriate for your car at that altitude.

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JayG · 02-06-2019, 07:45 PM

Unless you reprogram the ECU for 100 octane maytag is spot on

azlvr · 02-07-2019, 05:06 AM

The octane # is it's resistance to detonation. So unless vehicle is setup correctly it won't help. #Oxygenated fuel will help.

Lemming · 02-07-2019, 05:53 AM

Waste of $$$ unless you get a new tune. YMMV.

Cunningr · 02-07-2019, 08:53 PM

Our low octan gas here is 95 but I honestly can tell the car runs better on the 98 not really power wise but just smoother. I usally put high octan every other tank full. But I dont necassarily beleive its a required. You need to spoil your baby sometimes

Quadcammer · 02-08-2019, 03:00 AM

Quote:

Originally Posted by Cunningr

Our low octan gas here is 95 but I honestly can tell the car runs better on the 98 not really power wise but just smoother. I usally put high octan every other tank full. But I dont necassarily beleive its a required. You need to spoil your baby sometimes

Not the same octane rating scale

maytag · 02-08-2019, 04:02 AM

Quote:

Originally Posted by Cunningr

Our low octan gas here is 95 but I honestly can tell the car runs better on the 98 not really power wise but just smoother. I usally put high octan every other tank full. But I dont necassarily beleive its a required. You need to spoil your baby sometimes

Not sure where you're at, but you're probably looking at RON numbers. Not the same rating scale. (Unless you're regularly buying fuel at the racetrack).

From wikismedia:
"Another type of octane rating, called****Motor Octane Number****(MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON.****MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable****ignition timing****to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON"

RON is more common worldwide, but RON has been the US standard for a long time. (Though we're beginning to see RON listed at many US pumps)

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Flavor 987S · 02-08-2019, 04:47 AM

Here are 2 MAJOR problems with your idea/plan:

1) The 100 octane is not going to be very fresh. At a race track, yes, but NOT at your local corner gas station.

2) Unleaded race gas like this still has elevated levels of lead. If you don't beleive me, run a Blackstone UOA, and you'll see about 1-2 ppm on your next test result.

Cunningr · 02-08-2019, 09:39 AM

Quote:

Originally Posted by maytag

Not sure where you're at, but you're probably looking at RON numbers. Not the same rating scale. (Unless you're regularly buying fuel at the racetrack).

From wikismedia:
"Another type of octane rating, called****Motor Octane Number****(MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON.****MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable****ignition timing****to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON"

RON is more common worldwide, but RON has been the US standard for a long time. (Though we're beginning to see RON listed at many US pumps)

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I live in Spain by gas on US installation pump states 95 Octane in town pump tates 98 Octane, but on the base they are required post us rating. Will look to see if it say RON though.

Ciao · 02-08-2019, 12:25 PM

Quote:

Originally Posted by Flavor 987S

Here are 2 MAJOR problems with your idea/plan:

1) The 100 octane is not going to be very fresh. At a race track, yes, but NOT at your local corner gas station.

2) Unleaded race gas like this still has elevated levels of lead. If you don't beleive me, run a Blackstone UOA, and you'll see about 1-2 ppm on your next test result.

Actually (1) the pump is located near the Bandimere Race 1/4 mile race track. So, it is highly likely it is fresh. Though lead is used in racing fuels it is not used by itself, but mixed with Tetraethyl Lead. So in my example, mixing a small percentage of 100 with 91 to reach a 93 on rare occasions seems insignificant.

JayG · 02-08-2019, 01:54 PM

My understanding is any lead in the gas will kill the cats.

You will basically see no difference between 91 and 93 RON
The ECU will adjust for virtually any octane 93 and below

Flavor 987S · 02-08-2019, 02:27 PM

Quote:

Originally Posted by Ciao

Actually (1) the pump is located near the Bandimere Race 1/4 mile race track. So, it is highly likely it is fresh. Though lead is used in racing fuels it is not used by itself, but mixed with Tetraethyl Lead. So in my example, mixing a small percentage of 100 with 91 to reach a 93 on rare occasions seems insignificant.

Good, it's fresh.

If you keep running this race gas, do a UOA. I'll bet you start seeing 1-2 ppm of lead. BTDT.

Ciao · 02-08-2019, 04:15 PM

Quote:

Originally Posted by Flavor 987S

Good, it's fresh.

If you keep running this race gas, do a UOA. I'll bet you start seeing 1-2 ppm of lead. BTDT.

What does that parameter (1-2 ppm of lead) indicate? Avg? Normal? Abnormal?

Quadcammer · 02-08-2019, 07:17 PM

Regardless of the lead, what is the point? You have less oxygen at your altitude so you do not need 93.

Ciao · 02-08-2019, 07:30 PM

Quote:

Originally Posted by Quadcammer

Regardless of the lead, what is the point? You have less oxygen at your altitude so you do not need 93.

We do not have less oxygen; we can breathe, we have reduced air pressure.

maytag · 02-08-2019, 08:58 PM

Quote:

Originally Posted by Ciao

We do not have less oxygen; we can breathe, we have reduced air pressure.

Which results in less oxygen, by volume, in the cylinder. ;-)

You're both right. But ultimately it's the cylinder pressure which, as it increases, requires a higher octane (resistance to detonation). Thus: lower air density=less cylinder-fill=lower cylinder pressures = lower octane requirement.

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