My son needs help with a school project

[02cruizer]

Good Morning all!

My 12 year old son elected to do a project in science class on the effect of higher octane fuel in cars. He needs to know the effect it has had on more than one car. My car is one that we are using. I was using 87 octane, but when I moved to the 93, i noticed the car ran better and got almost 40 miles more per tank.

anyhow, he was hoping that some of you could post your mileage per tank on either (or both) type of fuel, and whether or not you noticed any difference in the performance of you car. This is due in 2 weeks. How little time there is for a single dad to do it all. lol

thanks all!

shawn

[LouisG]

I have a 1999 Ford Expedition - It has a 4.6L engine - I was told to use regular 87 octane and have since I got it - 21 MPG Highway

I also own a 1990 Buick Skylark GranSport 3.2L 6cyl - used to use regular 87 but it seemed to be getting a little sluggish coming out of a complete stop so I went up to mid-grade 89 octane and the sluggishness was gone - It really helped the performance.

I've only owned my 2004 PT for 3 weeks. It has the turbo-lite and I've used only 87 octane - like it says I should.

I don't know if I helped - but all data collected is a plus when it comes to homework.

LouisG

[1 bad white turbo]

ohhh! those days of homework!
I have 3 cars but one is my beater i use 87 in it.
my other two cars my PT Turbo and Mercedes s500 i use premium so i think its like 93? my 2 new cars perform awesome with the more expensive gas.
hope it all helps.

[GOLDMEMBER]

I have noticed that I get can drive at least an additional 50km on a tank on Super however in Canada Super runs $.10 + per liter more than regular

[PT_Sean]

Interesting observations so far. Technically, there is NO REASON why running high-octane would IMPROVE your gas mileage. Octane is an ignition arrestor, meaning that the more octane in the fuel, the later in the compression /ignition cycle it is until the fuel ignites and the power stroke begins.

The turbo (GT) requires high octane to ensure that the ignition takes place LATER in the compression stroke. Gasoline WILL "deisel", that is, ignite with compression/heat only. By having a higher octane fuel, it resists early ignition which would do major damage to your engine.

Here are a few articles talking about the octane/mileage thing...

Sean

http://www.car-forums.com/archive/t1288.html

http://www.handymanusa.com/articles/octane.html

http://www.leeric.lsu.edu/bgbb/7/ecep/trans/b/b.htm

http://www.google.com/search?hl=en&i...ne+%2B+mileage

[my80volare]

I've switched occassionally in my '91 Ford Probe (2.2L). I never noticed either an increase in milage or performance. Milage is about 320 miles/tank.

[Comedy Cruiser]

My PT runs about 22mpg on 87 octane.

I have noticed no difference in mileage or power when running 89 octane or higher. I'm just throwing money away when purchasing anything higher than 87.

Now a diesel, that's a different story!

[JOEM]

Originally Posted by PT_Sean

Interesting observations so far. Technically, there is NO REASON why running high-octane would IMPROVE your gas mileage. Octane is an ignition arrestor, meaning that the more octane in the fuel, the later in the compression /ignition cycle it is until the fuel ignites and the power stroke begins.

The turbo (GT) requires high octane to ensure that the ignition takes place LATER in the compression stroke. Gasoline WILL "deisel", that is, ignite with compression/heat only. By having a higher octane fuel, it resists early ignition which would do major damage to your engine.

Sounds like Sean has done your son's research for him.

[MX-5]

http://ptdoityourself.net/pitpass/report_octane.html

Here's the text:

February 11, 2001



There have been many "bench racers tales" about the use of high-octane gasoline over the years. The effects are worthwhile if you have three things: compression, octane and timing. High-test fuel and increased timing advance are only productive if there is sufficient compression.


Compression and Octane

The "Muscle Car" era is a perfect example. The Big-Iron domestic arena is full of 10.5 to 12:1 high compression engines. Those pressures are high enough to turn a few degrees of timing and 7 points of octane into horsepower; the first step in increasing motor efficiency. Keep in mind that 100 octane was the cheap stuff when those cars were built.

Today's cars, with 9 to 9.5:1 compression ratios, can't take advantage of high-octane fuel. Without the large cylinder pressure ratios, additional horsepower can not be generated.


Timing

Timing is no longer adjustable. The computer utilizes a pre-programmed timing curve with a knock sensor for safety. New engine designs bring up several questions:

1. Will high-octane fuel allow the (PCM) Powertrain Control Module to increase timing higher than standard fuels?

2. Does the PCM adapt to new octane through (STFT/LTFT) short and long-term fuel trims?

3. Does a "Block Learn" change the adaptive fuel strategy? (Resetting the PCM may teach it to advance the timing further than originally programmed.)


Test Conditions and Parameters

The test procedure took place over a 2000-mile range with information gathered in blocks. Results are grouped by similar variables. Temperature, humidity, barometric pressure, and calculated load values were the variables. Weight, track conditions, test equipment, driver, and vehicle are all constants. Tests were performed with the OTC 4000 Enhanced Scan Tool.


Test Results

The average of all recorded tests indicate these timing numbers:

1. Timing will increase to 23 degrees and build power 26 degrees at maximum rpm.

2. From a standing start, (CLV) calculated load value will increase from 76% to 88.2% with (WOT) wide-open throttle launches accelerating to maximum rpm. Rpm is electronically limited by the PCM.

3. No differences were recorded between regular and premium fuel, before or after a block learn.


Summary

These tests prove that the most efficient fuel is the lowest octane recommended by the manufacturer. Since the additive packages are the same for all grades of branded fuel, it's a proven waste of money and efficiency to run premium fuels.

The test results are real. No opinions or guessing was involved, only recording real information from the PCM datastream.

I have been proven wrong by my own tests. I honestly thought that I could squeeze a few degrees of timing advance from a block learn and premium fuel. Let's bask in the glow of knowing that we can keep $.30/gallon in our pockets.


Recorded by Motor- Mike



http://ptdoityourself.net/pitpass/re...fuelguide.html

Here's the text:

Fuel and Octane

A vehicle's fuel economy depends on the energy content of the fuel on which it runs. This has been determined by EPA and others and is consistent with combustion theory. Ethanol blended fuel may decrease mpg by about 2%. MTBE (Methyl Tertiary-Butyl Ether) oxygenated fuels reduces mpg by about 2-3% because they contain less energy than non-oxygenated gasoline. In addition, the energy content of gasoline varies from season to season. Typical summer conventional gasoline contains about 1.7% more energy than typical winter conventional gasoline.

Octane ratings measure a gasoline's ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders.

Most gas stations offer three octane grades: regular (usually 87-octane), mid-grade (usually 89-octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.

Stock PT's should use 87-octane fuel for optimum mpg. PT's with a supercharger or turbocharger should use 92-octane. Expensive high-octane gasoline (premium) does not give your car more power or better mpg. According to the AAA premium gasoline sells for an average of 17 cents more per gallon than regular gas. Only about 6% of cars sold in the U.S. need premium gas. Still, premium gas accounts for 20 percent of all gas sold. Resist the urge to buy higher-octane gas for "premium" performance.

The only reason to use high-octane gasoline is if your car knocks or pings on your normal grade of gasoline, and your mechanic has been unable to find any other easily fixable cause. The PT uses a "knock sensor", which detects knocking and protects the engine by retarding the ignition timing, however it can't compensate for a severe malfunction, a condition which can affect engine performance, fuel economy, or even damage the engine.


There is a lot more info about all this at www.ptdiy.net

[bigjim]

The word Octane is only used to tell you the point in which Gasoline will Knock. You can raise or lower octane by adding products like Toleune or mtbe or butene. or alcohol.Most gasolines today start off with a base of around 65 octane then other cheap products are added to get the Octane up to the average of 87 Octane. If you put 93 in your car or truck you will not get any more improvement in anything in your engine. Unless that engine is designed to run on a high Octane.Our test engines are designed to knock on 87 octane. Or any other grade of fuel that you put in them. As hard as this is to understand the engines that are used to test Octane have a cylinder that raises or lowers as the engine is running. These engines are made special by one company in the world and all testing labs that test Octane use the same type of engines. One is the reaserch motor and the other is the Motor motor .The best way to get the true meaning of Octane is have your son go to the Library and look up the ASTM manuel for Octane testing ,that will Explain a whole lot. or try www.waukesha.com That the company that makes the test engines.