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How much you save depends on how much you drive... I have 90,000 Miles on my car.


If you are running a Turbo.. They yes its probably a good idea to run Higher ocatne... But dont fool your self, it doesnt burn better or any thing. It just resists exploding under preasure better. (Turbos just UP the compression ratio of the engine to make more power)

 
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Your inquiry has been forwarded to us here at Chevron Fuels Technical Service.

Heat Content

Chevron does not and is not required to test its gasolines for heat content.

The Auto/Oil Air Quality Improvement Research Program calculated that conventional (non-oxygenated gasoline whose composition and boiling profile were equal to the U. S. averages for these properties would have a net heat content of 114,900 Btu/gal. Oxygenating this gasoline with 10 volume percent ethanol or 15 volume percent MTBE would lower its heat content about 3% to 111,400 Btu/gal.

Traditionally, premium grade gasoline has had a slightly higher heating value than regular. The difference-less than 1%. The differences likely to be less or non-existent between grades of reformulated gasoline.

There can be differences in heating value among batches of gasoline from the same refinery or among brands of gasoline from different refiners because of compositional differences. The differences are small and there is no practical way for the consumer to identify the gasoline with a higher heating value.


Burn Rate

There is no credence to the idea of different rates of burn for the different octane fuels.

There is no correlation between octane (fuel grade) and the concept of slower or faster or hotter or cooler running of engines. Chevron supreme gasoline will not burn hotter than the other grades.

Gasolines with oxygenates (ethanol or methyl tertiary butyl ether - MTBE) may burn hotter than those without oxygenates, but the octane has nothing to do with it.

There are a number of text books on internal combustion engines. Two well known authors are J. B. Haywood (MIT) and E. F. Obert (Northwestern University). They both discuss flame speed.

Flame speed in a spark-ignition engine is more controlled by the engine design and operating conditions than by fuel hydrocarbon composition. The design of the combustion chamber and inlet ports and how they affect turbulence is most important. A turbulent motion of the fuel-air mixture increases the speed of flame propagation by rapidly intermingling the burned and unburned portions of the flame front. Increasing engine speed increases turbulence and flame speed. Fuel-air ratio also is very important with the fastest flame speed occurring at slightly rich of the stoichiometric (chemically correct) air-fuel ratio.

Fuel composition also can affect flame speed. The gaseous fuels, methane and propane, have higher flame speeds than gasoline. Methanol has a higher flame speed than the gaseous fuels. In gasoline, isooctane (a paraffin) is about 20% slower than benzene (an aromatic). Benzene has a similar flame speed to 1-hexene (an olefin). Flame speed does depend on composition. However, it is just not directly related to octane level, but, rather, on the compositional makeup of a particular fuel. Thus, there is no direct correlation between octane rating and flame speed. Octane rating is only a measure of resistance to knock, or delay before autoignition.

From the above fuel discussion it is concluded that although the composition will vary between regular and premium gasoline the difference in flame speed is very small and no correlated with octane level. Further, the fuel composition effect is small compared to the engine design and operating factors.


Additives

Most gasolines contain negligible amounts of gum when they are manufactured, and most contain ("stabilizers') to retard gum formation. It is stabilizers that make it possible to store Chevron gasolines for a year when the conditions are good.

Detergent type additives:

Our Supreme gasoline contains the same ratio of Techron as our regular and mid- grades.

All our grades of gasolines have the same amount of Techron to maximize performance and minimize emissions in the great majority of vehicles, Chevron Supreme is designed for use in those cars that perform better with a higher octane gasoline.

If you are able to access the INTERNET please visit Chevron's website at www.chevron.com. Within that site there is a listing of available Chevron publications that deal with the subject of fuels, additives, oxygenates, etc. The publication entitled, "Motor Gasolines Technical Review" should be

of special interest to you. Just click on the titles to open the publications. The site is at:

http://www.chevron.com/prodserv/fuels/

Other sites to visit that talk about Techron would be:

http://www.chevron.com/prodserv/fuel...dvantage.shtml


http://www.chevron.com/prodserv/fuel...ch%5Fcon.shtml


http://www.chevron.com/prodserv/fuel...ch%5Fgas.shtml

http://www.chevron.com/prodserv/fuel.../history.shtml

http://www.chevron.com/prodserv/fuel...as/index.shtml

 
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Maybe the condition of your pistons have to deal with the way u broke in your engine. I know this article may go agaisnt what most people think is the proper way to break in your engine but give it a read.
http://www.mototuneusa.com/break_in_secrets.htm

 
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There is so much misinformation in this thread its unreal. I'm glad zzyzx and usafstud has shed some truth on the subject.

 
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what gas do you pump?
arco, chevron etc...

 
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yes i was thinking the same! i was "misinformed" at one point too.

 
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anybody know anything about costco gasoline? is it cheap like arco or what??

 
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Read this!

http://www.garage-pak.com/pat%2Dgoss...-hot-stuff.cfm

 
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Just to let you know my info was all from the arco website. I didn't know how to put it all into words for u. So i just jacked their crap....I think people bascially just get confused on octane and hp. Its all misunderstood...and for a good point to because when people don't understand a product they just buy the "best" stuff and thats how companies make their money.

 
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newb

Please show me better evidence why I should use 87 octane on my civic with nitrous. If you think 87 is ok go try it out yourself and please let me know when your ordering your new engine.

 
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this thread didn't specify which octane to use for which type of car whether it be na or fi. don't instigate.

i just use 87 all the time. or if diesel is cheaper than unleaded (which it isn't anymore here in CA) you can do like they do in the philippines and run all your "unleaded fuel only" cars off diesel

 
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I really dont think it was the gas that left the carbon deposits... But rather the use of Nitrous on a relitivly stock engine.

as far as if you should use higher octane on a car running nitrous... Depends, are you getting detonation using the lower octane? if not, then its still a waste to run Higher then 87, If you are.... Then that would be a reason to run Higher octane rated gas.

 
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it was to my understanding that whatever your car calls for is what you should run in it. isnt there research that shows using higher octane can be worse??

 
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Unleaded car run with diesel.... BAD.... Are you familiar with soot. Diesel will clog your cat (take a look at a diesel engine and tell me if you see a cat), wiat untill you go to emmisions. Not to mention diesel has a higher sulfur content, that poisons your cat and creates acid rian. And diesels combution force is 32, gasoline is 16, diesel explodes with twice teh force of gasoline.

 
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Just for the record, octane rating is this:

pure iso-octanol (the harder to get of the two forms of octanol) is considered to have an octane rating of 100. 87% iso-ocatanol and 13% n-octanol has an octane rating of 87. Every other compound is then measured agianst 100% iso-octanol, for instance methanol, has an octane rating of 104, so it is 104% harder to ignite than iso-octanol.

You see this has little to do with carbon build up. Really it is more like the adative they put in to the fuel, try changing gas stations. But from what I have seen of other peoples pistons on this site, it isn't abnormal. Gearbox had heavy build up after only 20k (i think it was 20K) and he never sprayed or anything (that I know of).

What a company can do is take a low grade fuel, like say 80 octane octanol, and mix 5% methanol (which has an octane rating of 104) and get 87 octane. These addative have are more likely to cause carbon build up. Some of these addative are to raise the octane while other are for the enivroment.

Also keep in mind, methanol is bad, not for your engine but for all the plastic lines and O-rings, Shell uses methanol in their gas.

 
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I had the same buildup after 20k miles with regular use of chevron techron additive. So we know that one does nothing already. Are you gonna try different fuel treatments and see which one cleans that stuff off? I always use 89 now since compression is a bit higher.

 
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And yea, this was after 20k miles on 87 octane with normal driving. Keep in mind these pics were taken AFTER scrubbing them with brake cleaner. Still couldn't get them clean so we left it.

 
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Interesting! I'll just stick with what works, 87... worry about the expensive gas when I get a swap!!

 
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Those cylinders pictures(both sets) dont look bad at all. Looks pretty normal from what I've seen(my dad is a mechanic, I've been around cars all my life). What you should be more concerned about is the build up of carbon around the valve stems.

 
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Thank you for crying out loud.

 
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I'm staggered at the amount of misinformation in this thread, especially since me and zzyzx have covered this so many times over.

I will reiterate what zzyzx said then lock this.

Octane rating determines how resistant a gas is to detonation, ie, combusting before the ignition spark.

Some cars require higher octane due to the compression ratio or being FI'd.

If you put high octane gas in your car, you will NOT get more power. It does NOT burn cleaner, and it will NOT give you less carbon buildup.

Also, BECAUSE higher octane has a higher detonation resistance, it actually must get HOTTER than regular gas in order to burn properly. In some cases, you may actually cause more wear and tear and more unclean burning since your car will not be able to maintain a high enough temperature to burn the fuel efficiently.

Do not use anything over 87 gas in your car. It's a waste, and will burn more inefficiently in your engine, and will even cause you to run lean, hence the reason some of you notice the gas seems to "run out" quicker. It's your engine compensating for the fact that the a/f ratio is coming out of your engine lean, since not all of the gas is mixing and burning properly.

 
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great info by the way. good post.

you also reminded me, often times gas companies get midgrade by mixing the high and low octane gases.