Gas octane

[kjkim93]

Hey guys just a quick question. Is it fine to switch to a lower octane? I've been running 91 for the last seven years I had this car. Does it matter if I go one octane down? Just been wondering. As it ages if premium is worth it

 

[Ryda55555]

I switch it up everytime i fill up lol sometimes i'll put 91 sometimes 89 and sometimes 87
But i never let it go lower than half a tank so i'll still have some good gas to mix with the lower gas

But our trucks are meant to be running 87 and a lot of people said its useless running 91 but i still do it cause i feel it runs better lol

 

[djthumper]

As long as you don't have it tuned for the higher octane you will be fine.

 

[gmcman]

Will run perfectly fine on 87, it was designed to run well on it. Higher octane fuel will aid under heavy loads allowing slightly more spark advance and this is generally not felt in the butt-dyno under general easy driving.

The knock sensors work in an unperceivable fashion, the thing about the knock is when the ECM commands more ignition advance, the lower octane is more susceptible to detonation and the sensors will "hear" this before you do. When this happens the ECM remembers this and adjusts accordingly. There are two octane tables in our ECM in factory trim, when the ECM sees a fill up it opens the door for the higher octane map. If the ECM sees a lot of knocking with more ignition advance, it switches over to the lower octane map and stays there until the next fill up.

This makes it easier for the ECM to adjust using one table over both...less parameters to play with.

Now with a tune, I believe the parameters are set and when using a high octane tune you can end up with some knocking if you use low octane fuel since the ECM won't retard the timing as much...this is something the tuners will need to chime in on....I don't how much of that is true.

Either way, if you are driving normally and no towing then using more than 87 is a waste of money.

 

[MDBT]

If you're set on spending more for fuel (because it's sooooo cheap to operate a 15mpg vehicle already ) then you should spend your money on better quality fuel, not higher octane fuel.

 

[CaptainXL]

If you're set on spending more for fuel (because it's sooooo cheap to operate a 15mpg vehicle already ) then you should spend your money on better quality fuel, not higher octane fuel.

I swear that I have noticed this. We used to fill up at Costco with the 87 octane. But ever since we got a Sam's memberships we fill up there with 87. Sam's gas has more noticeable power to it.

Also another thing to note is that gas stations are no longer required to place those E10 stickers on the pump.

Recently I have started using 89 octane when towing and it has helped.

 

[triz]

Our trucks are meant to run on 87. With that being said, a tank of 93 every once in a while and some good injector cleaner like Techron or Amsoils PI Performance Improver go a long way to keep the fuel system clean and running top notch. Cleaning your MAF, and your throttle body every so often will also help keep your truck running smooth.

 

[CaptainXL]

Our trucks are meant to run on 87. With that being said, a tank of 93 every once in a while and some good injector cleaner like Techron or Amsoils PI Performance Improver go a long way to keep the fuel system clean and running top notch. Cleaning your MAF, and your throttle body every so often will also help keep your truck running smooth.

87 octane has the same level of cleaners in it than 93. Its the law. So with all due respect, that bit of advice is null. Keep up with the cleaners every so often though.

The reason I have been using 89 octane lately is to reduce the likelyhood of pcm retarding my spark. No retard = more power when towing. Towing a 6000lb trailer can really be a drag.

 

[DDonnie]

Federal law requires a minimum, I'm fairly certain it doesnt require that all gas at the same station have the same ammount of cleaners. Stations like shell put more cleaner in their higher octane gas and the federal minimum in the lower octane.

How is Shell V-Power® Premium Gasoline different than Shell Regular and Shell Mid grades?

•Shell V-Power is the highest octane Shell gasoline.
•Shell V-Power is the best, most advanced Shell gasoline designed to deliver optimum performance through advanced technology.
•Shell V-Power contains the highest concentration of the New Shell Nitrogen Enriched Cleaning System
•With five times the cleaning agents required by federal standards, Shell V-Power helps to clean up performance-robbing engine gunk even faster than Shell Regular grade gasolines.

 

[jonbo2002]

Federal law requires a minimum, I'm fairly certain it doesnt require that all gas at the same station have the same ammount of cleaners. Stations like shell put more cleaner in their higher octane gas and the federal minimum in the lower octane.

Donnie, I don't know about other states but in Michigan where we live all gas stations get their gas from the same place, Mobil, Speedway, BP dosent matter they all have the same additives. the only difference is some tanks and pumps are taken better care of, when I worked at a Mobil we had the filters changed regularly but we never added anything to the tanks like extra cleaners. I think alot of the ads you see on TV are just the companys trying to sound better then the next.

 

[DocBrown]

Premium is only worth it if the vehicle if the vehicle is designed to run it. I've had 2 "premium optional" vehicles, a '99 Catera and my '06 HHR. There is a difference with those but its marginal. Where I live premium is 40 cents a gal more right now. The small savings in mileage on my HRR is negated by the higher price.

On vehicles that are not designed to run premium, using it is just throwing money away. Better you run regular and send me a check for the difference. So yes, you will be able to run regular just fine. I have 150k on my TB and have never ran any other gas than regular.

As far as all gas stations getting the same gas, this is true. What isn't true is that they all have the same additives. The additives are added when the gas is delivered to the station. Each company has their own formulas for additives. That's what separates Top Tier gas from others.

 

[DDonnie]

As far as all gas stations getting the same gas, this is true. What isn't true is that they all have the same additives. The additives are added when the gas is delivered to the station. Each company has their own formulas for additives. That's what separates Top Tier gas from others.

That's what i figured. Also, love your avatar.

When i have my tune done, I plan to tune for 93 because costco and sams (both of which i have memberships too) always have it for 20 cents more than regular. $4.00 a fillup doesnt seem bad to me.

 

[Playsinsnow]

I'll add that on my first road trip in the TB out west I filled with shell all the way to Cali thinking using the same "gas" can not hurt it because I was filling up in some off the wall locales. After a month in Cali my O2 sensor went out. Service advisor told me TB's, he and his head mechanic own one, hate Cali shell gas and that they were tested with chevron(?). My TB ran like total crap, stalling/cel, with shell but only in CA! seriously! Maybe why chevron tech cleaner is so good for our rides?
Also, Colorado offers 85octane, no 87 on all my trips there. Supposed to be fine because of the elevation, but I put 89 in while there.

And the station I fill up at, only one on the way to work without deviating from route, offers 87&89 octane at the same price. Keep the tank wet with unleaded and the cap tight and all will be good.

They all get their gas from the same place. A refinery. Go watch the trucks pull out.

 

[DocBrown]

That's what i figured. Also, love your avatar.

Thanks! Too bad its the last season. But how long can Michael Westen remain a fugitive and still help people? I'll miss it when its over.

 

[Sparky]

I know there are differences in brands of gas because my old car would get the best MPG from BP gas. I'd consistently get an extra mpg from it. Thought that was interesting.

The Trailblazer, well, it doesn't seem to care mpg wise what I put in its tank.

 

[Wyle]

The base gasoline that comes from the refinery is the same for all dispensed brands. It's the custom additives, like Chevron's Techron, that makes them different at the pump.

 

[CaptainXL]

The base gasoline that comes from the refinery is the same for all dispensed brands. It's the custom additives, like Chevron's Techron, that makes them different at the pump.

Yeah well in reality its kind of the other way around.

Gasoline is manufactured by different distillers which varies in its composition/blending to a certain degree. However little. So is the amount of ethanol. Hense the reason people can tell the difference for both of those reasons.

Additives are usually kept at the lowest possible level which is legal. However higher octane blends sometimes have more cleaners in it. But that doesn't mean it will clean any better.

My local Costco gas with 5x the EPA level of detergents makes the truck run worse than the Sam's gas. Sam"s doesnt advertise the level of detergents in their gas so I am assuming it's the EPA legal minimum.

It appears that more and more vehicle manufacturers that recommend a minimum of 87 octane are indeed recommending higher octane when towing. In this case it would help sustain horsepower which is just what I am after.

 

[Wyle]

Yeah well in reality its kind of the other way around.

Guess that depends on where you live. Here in Tucson, practically all our gasoline comes through one Kinder-Morgan pipeline from El Paso and all tankers (shell, chevron, unocal, arco) drink from the same hose for local distribution. Its the main reason we often have lowest gas prices (currently $3.15).

http://www.azenergy.gov/doclib/energy/az_motor_fuel_and_supply_distribution.pdf

 

[tblazerdude]

12.75 mpg on thorntons, 13.9 mpg on BP. Last 2 fill ups. $4.19x19.8 gal and $4.35x18.9 gal (Both premium octane with a tune for premium.) I feel I may have driven more on the highway with BP gas, not sure. I struggle feeling a difference in any stations fuel. I try to use BP/Shell, but that doesn't always work out. I will try to pay more attention.

 

[willn513]

Yeah well in reality its kind of the other way around.

Gasoline is manufactured by different distillers which varies in its composition/blending to a certain degree. However little. So is the amount of ethanol. Hense the reason people can tell the difference for both of those reasons.

Additives are usually kept at the lowest possible level which is legal. However higher octane blends sometimes have more cleaners in it. But that doesn't mean it will clean any better.

My local Costco gas with 5x the EPA level of detergents makes the truck run worse than the Sam's gas. Sam"s doesnt advertise the level of detergents in their gas so I am assuming it's the EPA legal minimum.

It appears that more and more vehicle manufacturers that recommend a minimum of 87 octane are indeed recommending higher octane when towing. In this case it would help sustain horsepower which is just what I am after.

So help me understand this better. Is it more expensive (for the retailers) to add the different cleaners/detergents to the gasoline or do they end up saving money by cutting it with those chemicals? I am just wondering why most add the lowest legal amount. It seems weird to me that Costco would add 5x more than they needed to legally unless they had something to gain by doing so(as in saving $ by having put more additives in)

 

[Ryda55555]

So help me understand this better. Is it more expensive (for the retailers) to add the different cleaners/detergents to the gasoline or do they end up saving money by cutting it with those chemicals? I am just wondering why most add the lowest legal amount. It seems weird to me that Costco would add 5x more than they needed to legally unless they had something to gain by doing so(as in saving $ by having put more additives in)

Well thats what they do with drugs, so i dont see why gas is any different lol. Everyones out to make money, and if you think about it nitrogen is probably a lot cheaper

But i stole this from a website

To understand octane rating, you need to understand a little bit about how car engines work.

The engine's power comes from carefully controlled explosions of gasoline/air mixture inside the engine. To control the explosions, the gasoline must burn at exactly the right rate. This is controlled by the gasoline's chemical composition.

Gasoline is a mixture of many chemicals that burn at different rates. One chemical that burns at the right rate is isooctane. A chemical that burns too quickly is n-heptane. To describe how fast a gasoline burns, a scale was developed using these two chemicals. Isooctane is defines to have an octane rating of 100, which n-hepatine has an octane rating of 0. Octane ratings compare the burning characteristics of gasoline to mixtures of isooctane and n-hepatane.

For example, if a cheap gasoline burned the same way as a 50:50 mixture of isooctane:n-heptane, the octane rating would be 50. Gasoline with an octane rating of 87 burns he same way that a mixture of 87 percent isooctane and 13 percent n-heptane would burn.

 

[Ryda55555]

Heres anoter thing i stole haha just found out lower octane burns faster and higher octane burns slower because n-heptane is explosive while isooctane burns at a slower controlled rate (always thought higher octane burned faster giving more power)


Octane rating scale
n-Heptane is the zero point of the octane rating scale. It is undesirable in petrol, because it burns explosively, causing engine knocking, as opposed to branched-chain octane isomers, which burn more slowly and give better performance. It was chosen as the zero point of the scale because of the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey Pine and from the fruit of Pittosporum resiniferum. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings and do not give as precise a zero point. ChevronPhillips Specialty Chemical produces a specialized grade of high purity n-Heptane (>99.0%) from crude oil through precision refining and distillation that is used in the measurement of octane rating for fuels.

 

[CaptainXL]

12.75 mpg on thorntons, 13.9 mpg on BP. Last 2 fill ups. $4.19x19.8 gal and $4.35x18.9 gal (Both premium octane with a tune for premium.) I feel I may have driven more on the highway with BP gas, not sure. I struggle feeling a difference in any stations fuel. I try to use BP/Shell, but that doesn't always work out. I will try to pay more attention.

That's more proof.

... and just to back up what I was saying I stole something as well.

Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 4% more or less than the average, according to the US EPA.

Gasoline - Wikipedia, the free encyclopedia

 

[Playsinsnow]

[SAVEDGMAP][/SAVEDGMAP]

Heres anoter thing i stole haha .

... and just to back up what I was saying I stole something as well.



Gasoline - Wikipedia, the free encyclopedia

Thanks for citing the source
Wikipedia though? Lets find a better source

I wasnt going to say anything but now I had too

 

[CaptainXL]

It's a quote from the EPA. They said it. I am sure they know.

Check the end of the paragraph on that Wikipedia page about gasoline again. See the Note? Go down to the bottom of the page to #6. That entire paragraph is cited.

But I don't need a quote or PhD in petrochemical engineering to tell me that gas from separate refineries is different in some ways. The info is easy to find. You can just grasp that much by reading up on the ways gasoline is reformulated. Hell the bulk oil comes to refineries in different flavors from all over the word.

 

[Playsinsnow]

It's a quote from the EPA. They said it. I am sure they know.

Check the end of the paragraph on that Wikipedia page about gasoline again. See the Note? Go down to the bottom of the page to #6. That entire paragraph is cited.

Guilty. Didn't even read the link! Wiki has stepped up their game in recent years but ever since college I watch what I read. I should start a few wiki pages related to this site and the "greatest platform ever produced" lol. I'll take your word.

 

[seanpooh]

Just some trivia, all the gas stations in Wisconsin claims that "there isn't any ethanol in 93 Premium". They make a big deal about it putting signs everywhere on the pump.

Maybe someone from Wisconsin could give some insight on this.

 

[Playsinsnow]

Just some trivia, all the gas stations in Wisconsin claims that "there isn't any ethanol in 93 Premium". They make a big deal about it putting signs everywhere on the pump.

Maybe someone from Wisconsin could give some insight on this.

Well I can say that here in the great state of Minnesota that Oxygenated premium fuel is much better for classics and older motors. Buddy with a '36 chev coupe went head over heels when his local station had 92 oxygentated. Signs go up more so in summer than winter I would assume...

 

[MDBT]

Oxy fuel leans out the mixture and depending on the additives used can also have damaging effects on fuel systems when stored for significant periods of time. On modern EFI engines which adjust mixtures and whose fuel systems are hardened against ethanol this is less of a concern but for seldom used classic cars running older carbureted engines with more reactive components in the fuel system I might be a little queasy about running it.

No idea on the Wisky ethanol levels, would be interesting to test them though.