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Discussion Starter · #1 ·
I know that there is a difference between different octane gas (89 vs 91 vs 93+), but is there a difference between, for the same level of octane, say Shell 93 octane, vs BP Amoco 93 octane, vs Mobil 93 octane, vs Citgo 93 octane, etc..... The only difference I can think of is maybe the "additive" they put in?? And those "additive" even make any difference?
Thanks! :wink:
 

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I think most of them are about the same, given that some additives are different. I think Shell and Chevron market their additives heavily. Since prices for gasoline are rising so rapidly, the AAA here is advising everyone to shop aggressively. (Premium hit $1.96+ over the past week for the cheapest stations in the South Seattle area. In the north end it is higher.)

HOWEVER, Arco regular is the pits. I think they have some method of getting to the ragged edge on octane...I mean BARELY there. Even my Dad's old Chevy wagon wouldn't burn it.
 

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Discussion Starter · #3 ·
Thanks, SeattleSheila!! :)
The reason I asked is because around my area, the gas stations are mainly "non-premium" brands, and I have to drive out of the way if I want the "branded" stuff. :roll:
 

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Here's a simplified answer for your question - I can go into the chemistry of it all, but I think that would be overkill:
Every batch of gasoline produced by a refinery has to meet very specific government specifications for quality. Thus, every refinery has to make their gasolines to meet these specs. There are different specs for different octane rated gasolines. So, it is true that all gasolines are the same, at least when they come out of the refineries. In fact, it is common practice for refineries to buy gasoline from eachother to meet their individual demands.
However, the difference lies in the additives packages for each brand, and these additives DO matter. You may not notice in just trying out a few tanks of cheap gas in a relatively new car, but, over time, deposits from combustion build up in your engine which will adversely affect the performance of your engine and ultimately result in problems such as engine "knocking." The additives help clean these deposits and some additives are better than others.
Another effect of a good additive is that it helps the fuel burn cleaner and may give you a little better mileage. I personally do not know enough about gasolines to explain this, but it is likely true since it is a fact that the big three car companies all get good gasoline (Chevron) trucked to them for EPA testing. (Note, that they go through the trouble of trucking this gasoline hundreds of miles since Chevron does not market gasoline in the midwest, as you probably know).

There is no doubt that you also pay for marketing when you go for a big brand, but unfortunately, they are also the ones who spent money coming up with the good additives.
One option is to buy cheap gas and separately add a bottle of additive (i.e. techron) every so often. I don't know if that would actually be any cheaper though - plus it's a pain in the ass IMO.

Given all that I just wrote, no matter what brand the gas station is, still beware that it isn't unheard of for a service station to tamper (i.e. dilute) gasoline. Because of that, I try to be careful not to get gasoline from place that seems too cheap or if the station looks sketchy....

Hope that answers your question.
 

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VP500 said:
hell i paid $44 bucks for a full tank :pissed:
How did you manage that? :eek: :-?
~$2.75/Gal seems a little high. :-?
 

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Yah, well...my baby always gets Chevron. I guess I'm sold on Techron!
 

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Yeah, the bigger companies have different additives. Shell, exxon, chevron, etc they have their additives that they market. However, the advantages of the additives are up to the user. It really nothing you can feel and notice but I still fill up with it because it can't hurt either way. Also, i work at the costco gas station in west plano, and the reason why we have gas so cheap is because we use generic grade gasoline, no additives. This goes the same with all sams clubs, albertsons, and those big grocery or wholesale places becasue they need to keep it cheap. just an fyi
 

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Shiznit said:
Yeah, the bigger companies have different additives. Shell, exxon, chevron, etc they have their additives that they market. However, the advantages of the additives are up to the user. It really nothing you can feel and notice but I still fill up with it because it can't hurt either way. Also, i work at the costco gas station in west plano, and the reason why we have gas so cheap is because we use generic grade gasoline, no additives. This goes the same with all sams clubs, albertsons, and those big grocery or wholesale places becasue they need to keep it cheap. just an fyi
all gasoline has additives, regardless of brand. It's federally mandated.
 

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Cleo said:
Shiznit said:
Yeah, the bigger companies have different additives. Shell, exxon, chevron, etc they have their additives that they market. However, the advantages of the additives are up to the user. It really nothing you can feel and notice but I still fill up with it because it can't hurt either way. Also, i work at the costco gas station in west plano, and the reason why we have gas so cheap is because we use generic grade gasoline, no additives. This goes the same with all sams clubs, albertsons, and those big grocery or wholesale places becasue they need to keep it cheap. just an fyi
all gasoline has additives, regardless of brand. It's federally mandated.
yeah it has additives, but not any that will make any difference. It's still classified as generic grade. The trucker that drops my gas into the tanks told me about the generic grade, i'll look on the invoice the next time i get a load.
 

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It does get confusing when there is 55 different types of gasoline (in terms of additives and what not) being sold in the US depending on the market area, and what time of the year.

We in CA are screwed because we cannot import refined gasoline from other states. Gasoline here in CA is refined here to meet our states' requirements. Other states requirements for their gasoline will not fly here in CA.
 

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Those government mandate additives are there to meet local emissions regulations, depending on the area and time of year. They don't do anything to keep your car running right.
 

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what do most people here use?

i used to use sunoco all the time cuz they have 94 octane :crazy:
 

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Discussion Starter · #15 ·
Wow, these have been very informative to me!!
Guess I will drive the couple of extra miles to top my for gas the next time. :lol:
 

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^^^^^^^^^^^^^^^^^^

WTF? :eek: I hope nobody ever has that much spare time to read through all of that. I'm sure it's all good information if you planned on making your own gasoline, but even a chemical engineer and someone who has worked in the petroleum industry like myself, have no interest in staring at that text for more than 5 minutes :lol:
 

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Not all brands are equal.
I used to have a long commute that had very consistent traffic conditions.
I always filled my car up the same way, topping it up to the overflow tube, and on a level spot, I let the pump click off then topped off slowly to get consistent fills. Of course I always checked milage on the tank with the trip odometer.

Different brands of gas gave me differences of 3 to 5 MPG! This was repeatable week after week. The moral of this story is that the less expensive gas was not always the best bargain. That is my cost per mile driven was often lower when I paid up to 10 cents more per gallon.

What I don't know is what the root cause was. It could have been higher octane fuel allowed my engine to run more total advance and that allowed greater efficiency. On the other hand the fuel that gave the higher MPG may just have had a higher BTU content. Gas companies will adjust octane by adding things like alcohol, toluene, & zylene(spelling?).

I have been told that, all other things being equal, the fuel with the highest octane will have the lowest BTU content. It makes sense on the face of it, you start with crude oil in the refinery, and crack it(basically heat it and pull off components at different heights, according to volatility), a type of distillation process & the lower fractions contain more BTUs than the higher fractions, ie oil has more BTU than kerosene/diesel, diesel has more BTUs than low octane gas, & low octane gas has more BTUs than high octane gas.

My apologies to all you petro-chemical engineers out there for over-simplifying the process. Please chime in if I have screwed this up badly.
 

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vlad_a said:
VP500 said:
hell i paid $44 bucks for a full tank :pissed:
How did you manage that? :eek: :-?
~$2.75/Gal seems a little high. :-?
:lol: I paid the equivalent of US$2.55 per gallon for premium in Whistler, BC, Canada a few weeks ago...

Thank goodness for liters and a different currency. It didn't hurt until AFTER I figured it out... :wink:
 
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