Is all gas the same?

A&Q about 350Z

Does it matter where someone fills up? I've been hearing that some people say mobil is the best, but does it really matter? What about citgo, kwik trip, and speedway? Does it vary that much from station to station? The reason I'm asking is because I've been hearing reports that some fuel injectors are being sent back to GM due to what mechanics believe is a bad injector, but GM is finding nothing wrong with them. Could it be bad gas? Here in WI we have the reformulated gas which I'm sure doesn't help.
I've been having misfire issues with my bonneville, which is going in next week. My mechanic thinks it's an injector problem, but someone I work with says that I should try switching gas stations and see if that helps. I always fill up at Citgo and I always fill the silverado there also. I haven't had a problem with the silverado. What do you all think?

The reports about the injectors came from my local paper.

All fuel is differnt, and not just between brands, two mobil stations 2 miles apart might have quit differnt quality fuels in thier tanks.

There are so many variables that effect fuel quality that no matter where you go you are taking a chance that you might get bad fuel.

Something as simple as whether or not the tanker that delivered the fuel was properly sealed can effect octane rating by a few points.

Try useing a differnt station, and see if you notice a change, but usualy a misfire is the result of poor fuel or spark supply, rather than poor quality fuel.

Yeah, I used to drive a semi truck. The tanker guys all filled up at the same depot(or so they said). I know Amaco used to have a little window in the handle so you could see that their gas was clear. How it was clear when others were not was a mystery if it all came from the same depot pump??? I guess some of them filter it more or put in additives. It will be interesting to follow this thread.

Every country in the world has its own standards, and its own distrabution methods.

Here in NZ we have two standards that petrol must meet.
It must have a minimum octane rating of either 91, or 96, and it must all be lead free.

We then have 4 major suppliers, BP and Shell are the biggest, with about 35% of the market between them, then Caltex and mobil share about 25%. (caltex inculdes a subbrand known as Gas)
They are known as the big 4.

Then there used to be two independants.
One was challange, started by a local corperate it only lasted a few years before being sold to caltex and mostly closed down.
The second, which has been more successful is Gull, an Australian company that has made it into the NZ market.

The big 4 all share most of thier distrabution infrastructure.
They buy 96 and 98 octane fuel, and some 91 octane collectivly from overseas refinerys, and store it at the same terminals.
Most of the 91 is refined localy, from semi-refined crude also purchased collectivly. All of the big 4 have equal shares in the local refinery, and none of them agree on how it should be maintianed or up-graded.
They then employ thier own fleet of trucks to distrbute it (usualy independant contractors, who employ owner drivers) and these all fill up from the shared terminals.
Once the fuel is in the truck a company spefic additive is often added. Caltex for example add thier "Vortex" additive, which is basicly just some basic detergents etc which are claimed to help keep the engine clean of carbon deposits.
Whether or not they help is irrelevent to thier effect on the fuels actual performance, which is the same for all the big 4, since its the same fuel.

Gull uses its own storage terminals, and imports all its fuel and desiel from Australian refinerys and depots. Some is all refined in Australia from Australian oil, and some comes from the same overseas refinerys the big 4 buy from.
You don't however know what your getting, and chances are most of its all mixed up anyway.
The diesel however is low sulpher, much much lower than product from the big 4, since it comes from Australia it meets australian standards. The big 4 still get thiers refined at the local refinery, which is incapable of producing low sulpher diesel.

Fuel quality can vary quite radicaly between stations for a variety of reasons.
Here in NZ the most remote stations are up to 24hrs away from a terminal. Fuel sitting in the back of moving truck for that long gets tossed around a lot, and lot of the octane raising agents are unstable long chains hydrocarbons which seperate from the rest of the fuel, become gaseous, and if the tanker is not sealed escape to atmosphere.
Its not uncommon for the fuel coming out of the tanker to be 1-2 points lower than when it went in.

There are also several storage terminals around the country. Our biggest city, auckland, gets most of its fuel from the terminal in Tauranga, two and half hours drive away. It can sit in the auckland terminal for 2-3 days, and the tauranga terminal for a lot longer, maybe a week.
After sitting for so long, with 2 truck rides, first between terminals, then to the gas station, then sitting in the gas station tanks for a week or more its quite possible for the fuel to lose more 2-3 octane points. In the summer it might be as much as 4-5 or more.
Iv heard of whole tanker loads of aviation fuel being turned away, and having to be sold as 100+ race gas, instead of 104 octane aviation fuel. Thats 4 points lost in getting from the tanker ship to the airfield, and thats high quality, low tolulene aviation fuel, not poor quality cheap automotive fuel.

As a general rule here in NZ the best fuel will come from the busiest gas station that is the closest to the terminal.
The worst fuel will come from smallest quiteist gas station the furtherest from the terminal.
Its a rule that should work generaly all over the world, but in differnt countrys differnt gas stations have differnt supply, storage, and distrabution methods, which all effect fuel quality.

Excellent answer from Moppie.
The fuel system in Canada has a couple of extra variables.
All refiners make a 'winter' and a 'summer' grade of fuel. The winter fuel is more volatile and more easily vapourises at lower temps for quicker and easier starts in the winter (but the winter formula would increase evaporate emissions if used in the summer). It usually has a small quantity of ethanol (alcohol) to reduce the effects of water contamination from condensation, like a frozen fuel line. However, fuel may contain up to 10% ethanol anyways. It's sometimes added to reduce emissions.
Most fuel here also gets an additive called MTBE, which is an 'oxygenator' additive to reduce emissions. Its presence is contrivertial since it is a proven carcinogen and is banned in some other markets, like the US.
We have 4 major suppliers in eastern Canada, Petro-Canada, Esso, Shell, and Sunoco (Suncor).
Eastern Canada also has Irving.
There are several smaller independent chains, such as Pioneer and Suny's.
All the fuel seems to be interchangeable in terms of performance and appearance (perhaps their distribution systems are integrated??), except for Shell. It's stuff has a distinctive aroma and seems to ping slightly less than the others.

Did you maintance them? I saw this product on Two guys clean the fuel injectors... maybe you should try it or maybe you did already

ok i have studied gassoline and shit and taken test cot certified to work for the major corps and ues additives are different in different places like countrys and even states but in your own area its all the same like here in ny theres certant laws that state theres some additives in the whole state but different ones in nyc but it doesnt change how the gass works or anything and about if u should go to 1 gasstation or another the only thing that would should determine that is how long the gass sits in the tank like it will go bad after sitting there for a year but what gasstation dont refill there takes a little more often than that so what im saying is 1 all the gasstation in your area 1 probly get the gas from exactly the same place even if the delivery drucks arnt the same and 2 the area u live regulates whats in it. and about people thinking whater is mixed in with it the only way thats posible is if there were condensation in the big tanks and the gas was sloching around but it seperates into a seperate whater holding tank and the gas is also checked with a special paste that detects water

How did you study "gassoline and shit" without a dictionary? This post is very difficult to read.

Moppie, i talked to a guy in the UK a long while back and we got into a discussion about octane ratings. In Scottland they have ratings similar to Octane but they are slightly off. He said the lowest he could get was 91. but after doing some research, the way they rate their gasolien (petrol) is different so 91 over there is equal to about 87 octane.
a little food for thought.

I always forget this is an international board that is often used by people in more than just the USA. So...ya i live in the USA.

Florida is still part of the USA?? Who knew?

I am feeling more Canadian/Mexican these days. LOL

The area formerly known as florida is now the deviding line between the atlantic and the gulf of mexico.
its always funny to ask the wendy's Person:
"Co'mo donde tu' haga 'el aqui' después nadar et Rio Grande'"
How did you make it here after swiming the Rio, im so raceist. they usualy look at me funny or get very angry. i think the ones that look at me funny are the cubans.
anyway, back on subject.

'el Rio Grande' sorry

Within regions, the gas for the most part starts out the same. It arrives at a depot by pipe, gets stored, and is then loaded onto trucks. When the truck is nearly loaded an additive is added. The additive varies by cutsomer and is what makes Shell different than Mobil or whoever. Shop around and let your car decide which fuel it prefers and stick to it. (i.e. less knock, better starting, no hesitation, etc.) Realize also, that small non-franchise stations can buy their gas from anyone with any additive. Usually price will select their gas.

Octane rating is something that just gets more and more complex the more you talk about it.

There are two international standards, RON and MON, both tested for in differnt ways, mean slightly differnt things, and just to make it confusing, some countrys use the average of both as thier octane rating.
Its why US fuels are labeled as being lower than New Zealand fuels, when infact they are mostly about the same.

ROn and MON. jogging my memory. ya. i beleive the US uses MON? still not sure. octane, as you said, is very complex. as long as i know my engine is just on the verge of knocking but isnt then im good.

In the US we actually use the average of the two, (RON+MON)/2, which you can see on every gas pump in the US.and the numbers are achieved and averaged. RON stands for research octane number and MON stands for motor octane number. Both numbers are derived by testing the fuels in a variable displacement combustion apparatus, the difference being RON tests at i believe 800 rpm and MON at 1600 rpm. The way it works is the compression ratio is raised until the point of knock and the fuel is compared to standards.

As far as gas being the same, Public is right about all the fuel going through the same lines. Different refiners will all pump there fuel through the same lines, not all at once but some mixing does occur, to the designated depot and then the the refiners additive packages are added (Shell v-power for example)
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