[SSDan]

Originally Posted by URBAN LEGEND

Any known reason why some states have no 93?

Yes, in order to hit the EPA emissions requirements for several of the western states (especially CA) the gas has to be refined with less benzene (I think - if not benzene then its one of those "zene" elements). Benzene in gas helps boost octane but it also off gasses at fill up more (contributing to smog). By refining with less benzene the highest octane the refineries can produce is 91.

[rlarsen462]

Is it really advisable to use octane boosters regularly (like Torco/Boostane) in a GDI engine? I seem to recall these things would leave red deposits back in the day when I used them on port injected cars even.

Also, 91 only here in Colorado too. The local Mobil does have VP 100, as well as ethanol free 91 (not sure that would make any difference, might be worse?). I did notice the car feels different after a battery pull, it also seems to pull harder when it's cool out/at night, but this would be normal based on my experience with past boosted cars.

I might let the car full learn and see if it feels like there's timing pull and then try running half a tank of the 100 and see what happens.

I only have about 450 miles on it, still feeling it out.

[wnyzl11le]

Originally Posted by 19Nasty1le

Ultra94 from Petro here in Canada

I was just at Toronto Motor Sports park yesterday for an open lap day and wasn't able to find anything around but 91. I am not sure how close to TMSP you are but if you had an suggestion that would be great.

[SJFGTO]

The table for 91 octane in your tune is slightly less “aggressive” than at 93, and the additional heat generated by the SC could be an issue, but the tune should already account for that. We have 93 here in Georgia so I have not driven a LT4 on 91. I wonder though if part of the problem is related to something else, poor quality gas?

[Squatch]

92 is the best you can get here in Oregon, but several stations sell 100 if you have a container to put it in. (they wont pump it into a registered car)

[Homeless Junkie]

I fill up with 91 octane and haven’t had any problems.

I haven’t had any problems with my bike either. That was tuned for 93 back in Maryland.

[TMac2254]

I put 100 octane in my 2018 ZL1 and it fell on its face when I hit the pedal. Spoke to a local tuner and he said that the stock tune is not tuned for anything above 93 and the 100 octane was the reason it fell on its face when I stuck the gas pedal . Was kinda surprised at that but I guess it makes since.

[Rodan]

In for interest, and more discussion of additives...

Here in AZ we're also stuck with CA 91. Some tracks have 94, but it's not readily available. We also live at 5000ft.

[TJay74]

Originally Posted by SJFGTO

The table for 91 octane in your tune is slightly less “aggressive” than at 93, and the additional heat generated by the SC could be an issue, but the tune should already account for that. We have 93 here in Georgia so I have not driven a LT4 on 91. I wonder though if part of the problem is related to something else, poor quality gas?

There isnt a 91 or a 93 table in the tune, there merely is a "High Octane" and a "Low Octane" timing table. The only thing that determines if the vehicles use or the other is a recorded event of knock. if the ECM sees knock it drops down into the low octane table for some time until the event decays out, then it goes back up into the high octane timing table.

If you have access to 91 but no 93 and you have access to E85 you can add about 2 gallons of E85 to 91 octane fuel and it will raise the octane of the gas.

[SJFGTO]

Originally Posted by TJay74

There isnt a 91 or a 93 table in the tune, there merely is a "High Octane" and a "Low Octane" timing table. The only thing that determines if the vehicles use or the other is a recorded event of knock. if the ECM sees knock it drops down into the low octane table for some time until the event decays out, then it goes back up into the high octane timing table.

If you have access to 91 but no 93 and you have access to E85 you can add about 2 gallons of E85 to 91 octane fuel and it will raise the octane of the gas.

I used 91/93 to as opposed to low versus high timing tables because that seemed to best relate to the OPs post.

[DangerZL1]

Originally Posted by URBAN LEGEND

Any known reason why some states have no 93?

I'm going to guess and say that 93 octane is less likely to have a 100% burn than 91, since it burns slower. It would be more likely to increase emissions than 93.

[DenverTaco07]

Originally Posted by URBAN LEGEND

Any known reason why some states have no 93?

I believe in some states it's because the altitude negates use of higher octane to prevent detonation.

[DenverTaco07]

Originally Posted by Rodan

In for interest, and more discussion of additives...

Here in AZ we're also stuck with CA 91. Some tracks have 94, but it's not readily available. We also live at 5000ft.

is it Pres-kit, or Pres-cott?

at 5000 feet, I believe no need for 93.

[SFV1LE]

Originally Posted by ZL1 1LE

I’m in Cali and I’ve been using Race Gas race fuel concentrate since the very 1st tank. It gives me peace of mind from detonation and gives me all 650 / 650. It takes 91 to 95.

Just my opinion but... you should stop using that Race Gas race fuel concentrate. I've heard from many experienced mechanics and tuners that it will gum up the fuel system. with chemical residue--they've described seeing this in detail.

It's only meant for occasional use with drag runs etc. The only thing you should put in your tank is pure unleaded 91/93 fuel, and 100+ unleaded is ok. But even high octane leaded race gas like 110+ or C16 (assuming you use it planning to remove cats and replace O2 sensors) shouldn't sit for long periods in your tank. You need to use it soon or it can leave a lot of residue in tank/lines from additives or some other properties.

Your engine will be fine on 91 or 93, it's tuned to handle and adjust to any variance in octane, and 91 is pretty reliable--it's 87-89 where the variance happens with octane testing lower than 87-89 more often.