Regular unleaded vs premium

[john99gtp]

ahhhh

 

i just paid $30.15 to fill up the GTP

 

:willynilly::willynilly:

 

 

she was really empty though, took 13.2 gallons (usually takes 12.4-12.6)

[sonyman87]

...It dosnt burn slower but it takes longer for it to combust ...

 

HUH ?

 

Please splain dah differnece Lucy

 

ok. say each '*' represent an Octane

*******************************//***(87)

*******************************//*****(89)

*******************************//*********(93)

if they burn at the same rate wich one will finish last.

[ursus]

 

okay I keep track of MPG religously on all my cars.

 

I buy gas at only Holiday stations

they have 87/89/91 non oxy

 

 

94 GA GT 3100 Auto.

 

87 I get 22 mpg city/hwy Driving

89 I get 25.5 city/hwy

91 I get 28.0 city/hwy

 

take into acount I dont have Overdrive in the car damn leak in the vac.

 

in My STE I get 23 MPG city/hwy with 89

and I get 32 city/hwy using 91

I have only used 2 tanks of 89 in that car and missed the power and milage.

 

 

on a properly tuned and clean car you will notice a differance. the computer will notice the differance in the burn after about a tank or so and adjust to make maximum use of it.

 

 

Send these results to exxon/shell/sunnoco et al, Im sure they would like to advertise you get 25 to 40% get better mileage with premium, I wonder why they don't, gee, I guess its because the FTC (a gov agency staffed with dopey kids I guess) won't let them because in test after test it has been shown to be completely untrue, no difference.

 

A few pudrs can and do recognize the dif, the 3.1 has no facilities to and does not! The northstar for eg does and indeed because it does and advances the timeing a couple degrees when you fill with premium you get 2-5% better milleage, thats 2-5% according to GM not 25 to 40%, I guess you should send your results to GM to so they can advertise they get up to 40% better mileage as well. I wonder why they don't , perhaps their ad execs are just a bunch of dopey kids to.

 

This is waht exxon says and the other big oils blogs on the subject are similar just go check their web sites, nowhere do they claim better mileage not even 1%

 

"To find out what octane your engine needs, first check your owner's manual. The recommended level is often 87 octane. Some models have high compression engines which are designed to utilize the octane levels of 89, 91 or higher.

 

Ordinarily, your vehicle will not benefit from using a higher octane than is recommended in the owner's manual. But if your engine knocks or pings at the recommended octane level, you may need a higher octane gasoline to prevent the knock. Knocking may occur under certain conditions. A small percentage of vehicles may knock because of variations in engines of the same model due to manufacturing tolerances, or because of an unusual build-up of engine deposits during the first 15,000 miles of driving. Other factors such as extremely hot weather, changes in altitude or hard driving conditions (like towing a heavy load) may also cause knocking.

 

Many modern vehicles are equipped with an electronic device that detects and eliminates light knocking before you hear it. The devices suppress knock by retarding the spark. We believe that some of these vehicles may experience some deterioration of acceleration performance, without knocking, when operating under high engine demand conditions. "

 

And the reason that mileage doesn't improve is even in the few special cases they define is that it corrects knocking "under high engine demand conditions" not while cruising down the highway. If your engine is pinging while leisurely cruising down the hwy yuo have a serious problem that needs to be corrected.

[ursus]

...It dosnt burn slower but it takes longer for it to combust ...

 

HUH ?

 

Please splain dah differnece Lucy

 

ok. say each '*' represent an Octane

*******************************//***(87)

*******************************//*****(89)

*******************************//*********(93)

if they burn at the same rate wich one will finish last.

 

Octane levels in different grades are set by the ratio of isoctane versus heptane and other additives in the gas not by different length molecules, you are thinking of viscosity improvers in oil which use longer/coiled molecules. i.e. 87 and 91 are made of the exact same ingrediants they just have different ratio of those ingresiants

[f_399]

filled up the lumina for $31.00 at $2.06

 

how many gallons do Luminas have?

[ursus]

filled up the lumina for $31.00 at $2.06

 

how many gallons do Luminas have?

 

~16.5

[sonyman87]

...It dosnt burn slower but it takes longer for it to combust ...

 

HUH ?

 

Please splain dah differnece Lucy

 

ok. say each '*' represent an Octane

*******************************//***(87)

*******************************//*****(89)

*******************************//*********(93)

if they burn at the same rate wich one will finish last.

 

Octane levels in different grades are set by the ratio of isoctane versus heptane and other additives in the gas not by different length molecules, you are thinking of viscosity improvers in oil which use longer/coiled molecules. i.e. 87 and 91 are made of the exact same ingrediants they just have different ratio of those ingresiants

 

you are probably right i wanna go slap my chem 2 teacher now. tobad he quit the school.

[GnatGoSplat]

If there are any disbelievers that octane is nothing but an anti-knock measure, look at this from a company that would stand to gain by people needlessly buying Premium:

 

http://www.quiktrip.com/gasoline/myth.asp

 

Maybe I'm just a skeptic, but I think people who notice a difference on a low compression engine like 3.1's and such are really just noticing a placebo effect.

[joey b]

It is true. Octane ratings do not at all depict the length of the molecule. Pure octane has a horrible octane rating, 58 may be the number I've heard. Anything longer would not be octane, so the name octane in reference to gasoline is very misleading. A higher octane rating as mentioned is a measure of how volatile it is, but in reverse order. A higher octane fuel is less volatile, and hence does not ignite as easily.

 

However, a volatile molecule may or may not have as much energy as a less volatile molecule. I believe the term is initiation energy(ie). A high octane fuel will have a higher ie and not ignite as easily but may still have more energy overall. Acetylene has a very low initiation energy but overall has only 2 single bonds and a triple bond. This may seem to yield a very high energy release but it really just due to its extremely low ie.

 

As Jeorge stated. On the first tank of a different grade fuel you most likely will not notice much of a change in mileage, but in later tanks I have noticed a change.

[Dan94Z34]

My camaro does this. If I put 87 in it, the computer will automatically retard the timing to keep the engine from knocking. I've been putting in 90 octane 10% ethanol. I can;t tell much of a difference from 90 to 92 premium fuel. Plus 90 is about 15-20 cents a gallon cheeper than premium fuel.