So it's my understanding that C6's are fitted with a dual gas tank system. Should I still be adding an octane booster after the car is full on fuel or how would I approach this if there is anything special about it due to the dual gas tanks?

Only using because the car is tuned aggressively and knocks without an octane booster. I want to make sure the additive is benefiting me for a whole tank of gas, not just half or what have you.

 

I would use it as the manufacturer suggests

 

A bottle of octane booster will add to a 10 gallon gas tank.1 octane. so in short instead of running 93 octane, you will be running 93.1 no real difference. if its knocking retard the timing or get a new tune completely.

 

If you don't want to get a milder tune, consider alcohol or water injection instead of octane boost.

 

To answer your question, you need to add the octane booster before the tank is full. Maybe half when you start and the other half part way through.

But as others have said, most octane boosters have very little effect except to your wallet.

 

only TORCO, no over the counter stuff

 

32 oz of Torco + 10 galons of 91 octane = 102 octane.


I would recommend getting the car tuned properly.

 

The Torco claim that its octane accelerator is a racing fuel concentrate seems very misleading to me. The active ingredient in Torco is MMT, a manganese compound developed after lead was outlawed. While MMT does not kill catalytic converters as quickly as lead, it clearly is not harmless to them. Its use has been argued in the courts many times. Last time I looked, MMT was legal at low concentrations in the US for rural areas, but not legal in the so-called reformulated gas that is used in most major cities. No oil companies use it in their gas in the US, even in rural areas. If you use it regularly, your catalytic converter life will be reduced, with the only question being by how much.

As far as the claim of it being a racing fuel concentrate, racing fuel is blended from components that are naturally high octane, such as aromatics, isoparaffins, and sometimes oxygenates. But the highest octane of any such compound is about 125, so as others have said, adding a 16 ounce can of high octane racing fuel compounds to a 10 gallon tank will only boost octane by about 0.5. Boosts of several octane from 16 ounces can only come from organometallics like tetra-ethyl lead and MMT. Unless your car doesn’t have cats or you don’t care about their longevity, you should not use octane boosters that give a several octane boost from a small can. That’s because the only way they can deliver that much boost from that small a can is via organometallics, and organometallics are catalyst poisons.

 

Good information! I have a couple of cans in the garage and have used it sparingly.

LDB, do you know why using Torco changes the color of your plugs and combustion chamber to an orange tint? Is it the chemical MMT?

 

This is NOT a recommendation, but I do know that the Buick T-Type ('80s turbo cars) crowd uses toluene that you can buy at the paint store as an octane boost. According to them, way more effective at adding octane and way more effective on a dollar and cents basis. The last time I looked they had published formulas for making your own home grown octane boost that even included cleaners for your fuel system. And, no, I wouldn't either waste my money on octane boost or put toluene in my Vette.

 

Yes, that’s the manganese. When I say organometallic, it means a molecule that is mostly hydrocarbon, like gas or oil (that’s the “organo” part), with a manganese atom bonded into it (that’s the “metallic” part). The organo part is what keeps it a liquid, dissolved in the gas. But when it burns, the organo part burns away, leaving a manganese atom behind which does not burn. Some of that manganese metal plates out on spark plug tips, manifold walls, and of course the catalytic converter catalyst. It’s precisely the same thing that happened with tetra-ethyl lead in the old days, with the only difference being that manganese is not as poisonous as lead was, either to catalytic converter catalyst or to the humans that might be standing around the exhaust pipe. The way such metal becomes a hazard to humans is that when it’s released like that, it doesn’t form as clumps of metal that will fall to earth. It forms as microscopic solid particles, a super-fine dust that can very easily be carried in the air without settling to the ground, and then breathed into the lungs. While the seriousness of the hazard from manganese can be debated, no sensible person would believe it’s risk free.

 

If someone did want to go that route, the problem would be the quantity required. Toluene is about 110 octane, depending on how pure it is. So to boost 90 octane gas by 2 numbers, you'd have to use 10% toluene, or about 2 gallons per tankful.

 

Thanks for the all the info guys, I realize that most(read: nearly all) octane boosters are snake oil. I did a lot of research and the only two brands I would choose are NOS and Torco both of which use MMT and NOS out of those two because it's available locally to me.

My mods are not that extreme(LS2 full bolt-ons, cam) but switching to gas from the Pacific Northwest vs the stuff in the Midwest has proven to be a recipe for pinging. The pinging stopped when I added NOS octane booster. I don't intend to run it forever, until I can get in and get the car tuned properly.


So it seems I should be adding perhaps half the bottle when the tank is low and the other half when the tank is full? Otherwise I'll stick to what the bottle says, I was just wondering if there is a special process due to the dual gas tanks.

 

Ignoring the fact that I think boosters with MMT are a bad idea for the reasons in my earlier posts, the way the gas tanks work, it doesn’t make much difference how you add, because there is tank mixing. There’s no need to get fancy. Just add it when empty and then put in your gas. The way the fuel system works is that the fuel pump is in the driver’s side tank. It pumps gas up to the engine, but the engine does not consume everything that is pumped. The excess comes back to a siphon-jet in the passenger’s side tank. The stream of returning gas picks up gas from the passenger side tank and carries it to the driver’s side. So there is constant mixing between the tanks. If you have more than half a tank of total gas, the driver’s side tank is full and the gas coming to that tank from the siphon-jet’s discharge causes spillover from driver’s side tank, across the big tube at the top, back to the passenger’s side. If you have less than half a tank of total gas, the passenger side stays empty, and the siphon-jet is sucking air along with its returning gas stream.

If you do the simple thing as described above, when you drive away from the gas station, you will be driving on roughly 60% concentration of additive, but it will quickly equalize due to the mixing described above. If you want to get fancy to reduce the difference as you are driving away from the gas station, then you need to add half at the start, and the other half about 2/3 of the way through the fillup. If you did half at the start and half at the end of the fillup, you’d be driving away with a higher concentration of additive until the mixing equalized things.

 

I used to live in ohio, stick with shell gas.

Also air can be more dense here.

The best thing is to re-tune ASAP, there is a decent window in an n/a motor before it knocks, and if your past that its dangerous.

 

Google images of long-term MMT use.

 

The problem with all of these octane boost additives is that you never get the mixture right. Is the tank truly half full this time? What is half full? what if it's a gallon lower than last time? Or a gallon higher? Your octane is probably never the same twice, though those octane boosters normally don't do much. If your tune is such that your ping/no ping is changed by a bottle of octane boost, then backing out the timing just a touch probably wouldn't even be noticed and would be fat safer.

The above idea of an alcohol injection system is a really good one, if you really need to run the tune as it is. An alcohol boost system when set up well is at least giving you repeatable results to tune with.