I wonder how much is that octane boost I see in the auto stores. Would it get you from 87 to 89 cheaper than gas? Will have to check it out next time I am at Canadian Tire or some parts store.

 

^ Dont waste your time. Those octane boosters are worthless. If you want higher octane gas then buy higher octane gas, simple.

 

Did you know that for gasoline the higher the octane rating, the lower the energy per unit volume? Why is this? The lower the amount of energy, the less prone it is to ignition from heat and compression. High performance engines have higher compression ratios (cylinders compress fuel and air mixture to a greater pressure before ignition) and the lower octane fuels have a tendency to ignite under compression prior to the spark from the spark plug.

This is why engines designed for 87 octane have zero benefit from running higher octane fuel (no matter the octane, preignition does not take place). Hemi's are designed to sense if preignition of the fuel is taking place and can thus run on 87 or 89 octane gasoline.

 

Ok that sounds good.

 

Those octane boosters are bs. They claim to raise the octane rating 2 to 3 points, what they mean is 87 will now be 87.2 or 87.3 not 89.

 

Ouch! The price of your low grade is what we pay for 93. 87 is $2.47 here in Memphis. As for top tier gas stations, the same fuel trucks that are filling Shell/Mobil/Exxon are filling Walmart/Costco/and Uncle Billy's corner store gas station. It can be argued that the tank conditions might be better and the additives are different, but it's the same gas.

 

Very true, I remember about 15 years ago when an independent agency tested the octane levels of various gas stations and news agencies posted the results.The one constant was the higher octane fuel was below the 93 octane level by as much as 2 octane points.The 87 and 89 was usually below what was posted,but not by more than .5 octane point.I wonder what these agencies are doing now???? I hav'nt seen any numbers for over 10 years now.

 

I think all gas has the same energy per unit volume, it has nothing to do with the energy content of the fuel. Only thing that changes is the Activation Energy in which it takes to cause an explosion, that basically controls the tendency to react (burn, explode etc). The higher octanes have higher activation energy thus helping control misfires due to surrounding heat and other factors that do not include the spark plug going off. But that's just my understanding, I'm not an expert.

I was reading something about how they decide the octane rating on engines and it's something to do with Iso-Octane and Heptane. Depending on the percentage of Iso-Octane used in the test gives you your octane rating 90% = 90 89% = 89 etc etc. So the engine isn't really tuned for normal gas, or that nasty ethanol mixture. Which I think is the reason why personally my mileage has dropped, I need to find a gas station that doesn't use ethanol mixed in the fuel if there is such a thing anymore.

Interesting article on drop in mileage due to ethanol if you're bored.

http://www.americanfuels.info/2008/0...l-mileage.html