The Truth About Gas and Octane
 

Bare with me, I'd like a solid truthful answer to this:

Does the number in Octane Level Really Matter when you're filling up at the pump? I've never seen a noticable difference if I get better milage from higher octane VS. the lower octane! (Hub and I argue about this i.e. = saving $$ -& all....)

Currently in Northern CA. we're paying as much as $2.57 for the Premium gas at places like Shell - for example... the lowest octane is selling for $2.11 a gallon today. BTW - My car is a V6 automatic with overdrive.

Help, Oh Great & Wise tilted Motor Men!!

Well, depends on the car. Some cars want premium (see what is on the gas cap or gas area). But the higher octane just prevents premature firing of the pistons during compression. That is why with a spors car you will definitely want premium, especially if it is high compression.
My 2 cents.

if the car doesn't call for premium, and it's not pinging when you use regular, then you're wasting your money AND causing engine damage by using premium. You're wasting money because you don't need the expensive stuff. You're causing engine damage because you're getting a "dirty" burn which leaves deposits in the cylinder. Eventually those deposits build up, and when they get heated up by combustion, they stay hot until the next cycle, at which point they ignite the air/fuel mixture before the spark plug has a chance to. That causes premature detonation, or pinging, and you will then HAVE to stick with premium.

engines with high compression= need high octane gas.

lower compression = lower octane gas.

consult owners manual and dont buy any octane higher than it says---waste of $$

what others have already said...use the octane that your engine and manual call for. As your engine gets older, it may start to ping. Kinda sounds like that little ball in the spray paint can rattling around. At that point you need to upgrade to the next highest grade of gas to keep serious engine damage from occuring. If you are at the piont where you are forced to go up a grade, chances are you wont notice a difference in your wallet. The extra 10cents or so a gallon i pay on medium seems to be made up for by the slightly better mileage i get now that im not pinging.

Excellant input, I knew that you'd all have good imput for me!

HUGE THANKS! You are all wonderful.

hunny

If you don't have the compression to support the timing table, a higher oct. gas will burn slower resulting in LESS performance. Side note that I figured I would throw in :)

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

You are correct about that, but I don't believe that automotive fuel actually IS octane...the octane rating, as I understand it, just reflects a percentage rating of how resistant a fuel is to compression ignition, compared to pure octane...ie, 100 octane fuel would behave like octane, 90 octane would detonate at 90% of the pressure octane would, etc etc. It might not be an exact pressure percentage, but I am pretty sure that it is just using octane as a reference point.

Here is a similar thread by Tritium titled "The truth about petroleum." It has some very interesting information on octane rating and performance.

I must say that Tritum has got to be either a true genuis or a chemical engineer...

Wonder what He drives???