Most premiums are the same or similar. The higher the octane, the cleaner burning it is. The main differences is the amount of legally required detergents and additives in the fuel.

Some companies like Shell claim more than others, but you never really know.

The bigger concern is the way the fuel is transported and stored. If you have a newer station, the tanks may be newer and may contain less sludge or water in the fuel versus older stations with leaky or old underground tanks.

 

Higher octane rating does not have anything to do with how clean it burns. The octane rating refers to the fuel's ability to resist compression knock, predicted and experimentally determined value. The quality of the fuel refers to the amount of impurities (that will not burn) and the type of additives.

 

That is not correct. The higher the detonation, the less burnt fuel and thus the more that's left behind. The more carbon-carbon bonds left behind, the more carbon deposits are left on the piston and valves.

Higher octane means more dense fuel. These fuels can burn at a higher temperature and with more energy, which is cleaner and ultimately more efficient.

 

Sorry, you're not going to win over this chemist today.

http://en.wikipedia.org/wiki/Octane_rating

Any hydrocarbon (or partially oxidized fuel, like ethanol) fuel will burn efficiently with the right fuel/air mixture. To say that the "higher detonation" equals more burnt fuel is absolutely not true (read the link). The more carbon-carbon bonds left behind (whether you are making charcoal, graphite, haha-diamonds, or even Bucky *****) just means that your vehicle needs service. The most common other hydrocarbon in your fuel is n-heptane, which tends to compression knock at lower pressure than does octane isomers. Removing the heptanes (higher rating) requires better distillation techniques to separate it from the slightly higher boiling octanes (fractional distillations). If you have fuel left behind (rich condition), then you may need to tune up your motor. Higher octane fuel is not more "dense" by any means. The only thing that it may contain is one more C-C bonds per mole to allow for slightly more change in reaction enthalpy upon oxidation. So, yes, the higher octane fuels can burn slightly hotter, but the only way you will ever see the advantages would be to boost the air (high pressure or compression ratio). I disagree with the higher octane fuels burning cleaner and more efficiently, if you are running a stock 150. The octane ratings just indicate the resistance to detonation under the same pressure with isooctane as the standard (100 rating). Density is defined as the mass (grams) per unit of material (usually milliliters). Like water = 1.0 g/mL. Isooctane is about 0.69 grams/milliliter and benzene is about 0.88 grams/milliliter, but they have almost identical octane ratings (100 vs. 101).

 

So what are you trying to say?

 

OK, OK! I got carried away. I am saying that higher octane fuels do not burn more efficiently than lower octane fuels in a N/A vehicle, do not leave more deposits on the combustion chamber components, and do not have anything to do with density. As far as the heptane stuff, I was just trying to give an example of a lower octane rated fuel for detonation purposes.

Roush150,
I'm not doggin ya, but just trying to back up my statements.

 

I'm so confused!

 

You may be right, but how come running premium fuel on a premium custom tune (AKA upped timing etc) can shave seconds (yes, SECONDS) off a 0-60 time over a 87 octane tune? just curious...

 

what kspence is saying is that buying the premo gas does not make you run cleaner. and in motors not designed to run with it you have little to no gains (without tune).

now when you have a tuner on your truck and run it in 93 mode, the computer assumes (does not know what grade you have) and will change the timing to rich or lean out your gas into your truck, lean is more power but hot, alter the timing and fuel and you can lean the truck out and make more power, 93 runs cooler than 87....if one runs 87 on a 93 tune they would run the risk of burning to hot, not to the point of really damaging engine, but burning out the cats with an exhaust gas that is too hot.

but back on to it, kspence is correct, 93 does not burn cleaner just cooler and needs/likes a little more compression, hence high performance cars like a vette or porche run a higher compression, and state only 93....our truck only 87 is suggested with lower compression

 

It's simple. In the same engine, with the same compression ratio using both fuels, using the higher octane fuel allows more timing advance without detonation (pinging). The more advanced timing allows maximum cylinder pressure to occur at the best possible time in the piston stroke, leading to more power, and shorter 0-60 times.

 

Yes, yes, and yes. Thanks guys, I was a little tired when I typed that "mess".