El Cheapo Gas

[sockgirl77]

A whole what?

lot of nuffin

 

[Speedy70]

lot of nuffin

 

[pixiegirl]

A whole what?

A whole lot of empty space.

I can't complain. 130K and I've not had any big problems with it. Matter of fact nothing over a couple hundred bucks and that was only once. So other than routine stuff I've had one issue that cost me I think around $250 or so. I have a couple piddly things now (dash light that's on, cig lighter doesn't work) but I'm not pressed.

I'm going to try 91 octane and see what happens.

 

[Lugnut]

For a car that is designed to run on 87 running premium is a waste. You may eek out 1 or 2 mpg increase in mileage but you have to do the math and see if it is really beneficial due to the extra .20 a gallon. However, it will not "ruin" your car to burn 87.

Gasoline is a petrochemical that is a mixture of carbon chains of various lengths. The name of the molecule chain is based on how many molecules make up the chain, pentane, octane, septane. Most of the molecule chains are stable but can ignite under pressure like the compression stroke of the piston before the plug ignites causing premature ignition or "knock". In high compression engines it is common for them to recommend 91 or 93 Octane gasoline. Octane is one of the carbon chains that is VERY stable and will not ignite during compression. All gasoline has some octane but premium or 93 has a greater percentage of Octane to prevent knock or premature ignition. That being said when they refine crude oil one of the smalleds yeilds is octane so it costs more.

**I didn't make this up I read up on it a long time ago

A couple minor quibbles with the above statements.

First, "Octane" isn't a substance. It's a rating for the resistance to auto ignition of a fuel.

Second, if you switch to premium and see an increase in MPG then you are quite possibly damaging the engine using lower octane gas.

Vehicles with knock sensors retard timing when detonation is detected. Detonation is a BAD thing and can be caused by a number of things, the most common of which is a combination of low octane gas and heavy engine loads.

In the worst case (Hi performance engine being pushed to the limits) detonation can damage pistons, valves, rods, etc. In your every day car detonation gradually eats away at the head gasket and pounds the rod and crank bearings out of tolerance causing oil pressure loss and oil starvation farther up the oil pathway. Eventually, if allowed to continue, the head gasket or bearings will fail.

The simple answer is to run the manufacturers recommended octane. BUT, depending on your engine and driving habits, minimum octane gas may not be enough to eliminate detonation. If you have a lead foot USE HIGHER OCTANE GAS. If your engine has a turbocharger, supercharger or high compression motor, USE HIGHER OCTANE GAS.

 

[desertrat]

A couple minor quibbles with the above statements.

First, "Octane" isn't a substance. It's a rating for the resistance to auto ignition of a fuel.

Second, if you switch to premium and see an increase in MPG then you are quite possibly damaging the engine using lower octane gas.

Vehicles with knock sensors retard timing when detonation is detected. Detonation is a BAD thing and can be caused by a number of things, the most common of which is a combination of low octane gas and heavy engine loads.

In the worst case (Hi performance engine being pushed to the limits) detonation can damage pistons, valves, rods, etc. In your every day car detonation gradually eats away at the head gasket and pounds the rod and crank bearings out of tolerance causing oil pressure loss and oil starvation farther up the oil pathway. Eventually, if allowed to continue, the head gasket or bearings will fail.

The simple answer is to run the manufacturers recommended octane. BUT, depending on your engine and driving habits, minimum octane gas may not be enough to eliminate detonation. If you have a lead foot USE HIGHER OCTANE GAS. If your engine has a turbocharger, supercharger or high compression motor, USE HIGHER OCTANE GAS.

According to "How stuff works' (and what I remember from chemistry)
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.

 

[sockgirl77]

A couple minor quibbles with the above statements.

First, "Octane" isn't a substance. It's a rating for the resistance to auto ignition of a fuel.

Second, if you switch to premium and see an increase in MPG then you are quite possibly damaging the engine using lower octane gas.

Vehicles with knock sensors retard timing when detonation is detected. Detonation is a BAD thing and can be caused by a number of things, the most common of which is a combination of low octane gas and heavy engine loads.

In the worst case (Hi performance engine being pushed to the limits) detonation can damage pistons, valves, rods, etc. In your every day car detonation gradually eats away at the head gasket and pounds the rod and crank bearings out of tolerance causing oil pressure loss and oil starvation farther up the oil pathway. Eventually, if allowed to continue, the head gasket or bearings will fail.

The simple answer is to run the manufacturers recommended octane. BUT, depending on your engine and driving habits, minimum octane gas may not be enough to eliminate detonation. If you have a lead foot USE HIGHER OCTANE GAS. If your engine has a turbocharger, supercharger or high compression motor, USE HIGHER OCTANE GAS.

So, if I slow down I can use the cheap shit?

 

[Pete]

A couple minor quibbles with the above statements.

First, "Octane" isn't a substance. It's a rating for the resistance to auto ignition of a fuel.

Octane IS a substance:

Octane is an alkane with the chemical formula C8H18. It has 18 isomers.
Octane has 18 isomers :

Octane (n-octane)
2-Methylheptane
3-Methylheptane
4-Methylheptane
3-Ethylhexane
2,2-Dimethylhexane
2,3-Dimethylhexane
2,4-Dimethylhexane
2,5-Dimethylhexane
3,3-Dimethylhexane
3,4-Dimethylhexane
2-Methyl-3-ethylpentane
3-Methyl-3-ethylpentane
2,2,3-Trimethylpentane
2,2,4-Trimethylpentane (isooctane)
2,3,3-Trimethylpentane
2,3,4-Trimethylpentane
2,2,3,3-Tetramethylbutane

Second, if you switch to premium and see an increase in MPG then you are quite possibly damaging the engine using lower octane gas.

I disagree. If your car runs on 87 without knocking, BUT gets 1 mpg better using 93, it does not mean the 87 is damaging the engine.

If your car knocks and pings with 87 then certainly something is is being damaged.

 

[Lugnut]

Octane IS a substance:

Octane is an alkane with the chemical formula C8H18. It has 18 isomers.
Octane has 18 isomers :

Octane (n-octane)
2-Methylheptane
3-Methylheptane
4-Methylheptane
3-Ethylhexane
2,2-Dimethylhexane
2,3-Dimethylhexane
2,4-Dimethylhexane
2,5-Dimethylhexane
3,3-Dimethylhexane
3,4-Dimethylhexane
2-Methyl-3-ethylpentane
3-Methyl-3-ethylpentane
2,2,3-Trimethylpentane
2,2,4-Trimethylpentane (isooctane)
2,3,3-Trimethylpentane
2,3,4-Trimethylpentane
2,2,3,3-Tetramethylbutane




I disagree. If your car runs on 87 without knocking, BUT gets 1 mpg better using 93, it does not mean the 87 is damaging the engine.

If your car knocks and pings with 87 then certainly something is is being damaged.

Sorry, should have been clearer. "Octane" as it's being referred to here is a "rating" so named because it's rated as a comparison to an Octane (the substance this time) derivative. Confusing huh?

In fact not all gas is the same, and liquid gas for transportation use consists of different mixtures on any given day based on what a refinery has on hand and the specifications of the various companies.

With regard to the mileage/damage/knock issue. Not all knock is audible, you can have predetonation in a cylinder without ever hearing it. BUT all knock causes a reduction in mean pressure in the cylinder which translates to less power/efficiency which then translates to less mileage and power output. I stand by my statement that detonation over time (Even detonation you can't hear) causes the damage I mentioned above.

I have some REALLY cool graphs of real time in cylinder pressure measurement that show teh effect of lower octane on engine efficiency and some pics of catastrophic damage caused by not retarding timing when the detonation was detected. These came from an IHRA top fuel funny car I instrumented a few years ago. NEAT STUFF!!!

 

[sockgirl77]

Speaking of funny car...

Driving Force is an awesome show. Man, I love me some John Force.

 

[Lugnut]

Sorry, should have been clearer. "Octane" as it's being referred to here is a "rating" so named because it's rated as a comparison to an Octane (the substance this time) derivative. Confusing huh?

In fact not all gas is the same, and liquid gas for transportation use consists of different mixtures on any given day based on what a refinery has on hand and the specifications of the various companies.

With regard to the mileage/damage/knock issue. Not all knock is audible, you can have predetonation in a cylinder without ever hearing it. BUT all knock causes a reduction in mean pressure in the cylinder which translates to less power/efficiency which then translates to less mileage and power output. I stand by my statement that detonation over time (Even detonation you can't hear) causes the damage I mentioned above.

I have some REALLY cool graphs of real time in cylinder pressure measurement that show teh effect of lower octane on engine efficiency and some pics of catastrophic damage caused by not retarding timing when the detonation was detected. These came from an IHRA top fuel funny car I instrumented a few years ago. NEAT STUFF!!!

Hey Pete, found a quick explanation that might help a little bit. Click me!