Gas question-

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ZR1fan

ZR1fan

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Is there a significant difference in the quality of gas at lets say an Exxon vs. some other cheap gas station? I've always been curious to know, like have you noticed your car runs better on one brands' 87 octane vs. another? Two of my cars (the Accord and Odyssey) get their gas from a discount station near here, the third one (the Pilot) I take to the Exxon down the street, sure it's more expensive (by 6-10 cents a gallon) but someone told me their car runs better on Exxon, and I have noticed it is a bit smoother on the Exxon stuff but I just wanna make sure it's not in my head.

Also- last question, I'm considering upgrading the octane of the gas I put in it from 87 to 89, does switching the gas out mid way have any ill effect on the car? My Pilot is getting up there in age and mileage, and absolutely anything I can do to ensure it runs as healthy as it does now for a very long time I want to do.
 
I have no idea which brand of gasoline is better. I do know that octane is a measure of knock resistance, so running an 87 octane car on 89 won't do much good. However, if your Pilot recommends 89 or above, and you're running it on 87, it would last a bit longer if you ran it on a higher grade fuel. Generally, an engine designed to run on a higher octane fuel will make less power when given a lower grade gasoline. I hope this helps.
 
Beeblebrox237
I have no idea which brand of gasoline is better. I do know that octane is a measure of knock resistance, so running an 87 octane car on 89 won't do much good. However, if your Pilot recommends 89 or above, and you're running it on 87, it would last a bit longer if you ran it on a higher grade fuel. Generally, an engine designed to run on a higher octane fuel will make less power when given a lower grade gasoline. I hope this helps.
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It's designed to take regular- the 87 stuff, alright yeah that clears things up a bit, good to know I'm treating it right, I just wonder what's the difference between brands now
 
ZR1fan
Is there a significant difference in the quality of gas at lets say an Exxon vs. some other cheap gas station? I've always been curious to know, like have you noticed your car runs better on one brands' 87 octane vs. another? Two of my cars (the Accord and Odyssey) get their gas from a discount station near here, the third one (the Pilot) I take to the Exxon down the street, sure it's more expensive (by 6-10 cents a gallon) but someone told me their car runs better on Exxon, and I have noticed it is a bit smoother on the Exxon stuff but I just wanna make sure it's not in my head.

Also- last question, I'm considering upgrading the octane of the gas I put in it from 87 to 89, does switching the gas out mid way have any ill effect on the car? My Pilot is getting up there in age and mileage, and absolutely anything I can do to ensure it runs as healthy as it does now for a very long time I want to do.
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If your car is meant to run on 87, run it on 87.
As for differences between brands, yeah, those additive packs really do make a big difference. Shell has been best for my Honda Fit by quite a bit. I get 30-35 more miles per 10 gallons compared to BP/sam's club/thorntons.
Then there's even differences from station to station of the same brand.
 
In regards to the OP, generally no, but that can vary, especially in NY.
 
I the UK I've noticed that my car runs much better on the petrol I can get from what I'd call actual 'gas' stations as opposed to the ones that are affixed to places like asda/morrisons/etc.

The MX-5 doesn't seem to run any better on super unleaded (97+) in comparison to when it's ran on 95 so I only ever occasionally put 97 in just for a flush through the system.

I run the AE86 on 97 at a minimum though since I really don't know if the previous owner had it mapped to run on 95 or 97+, I have noticed though that it seems to start better when ran on 97 as opposed to 99.

Talk of 95 as low grade petrol must seem weird though to all of you in the US :p

(All values are UK/EU RON numbers, UK to US values are: (97=92.15), (95=90.25), (99=94.05) )
 
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Tiddy
Talk of 95 as low grade petrol must seem weird though to all of you in the US :p
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Only because its measured on a different scale. You don't have "better" fuel.
 
Actually I was thinking of this today. Usually I fill my truck up at the Vallero down the street. It's the cheap gas station. But on the way home today I filled up at a brand new Shell station. I noted that my truck felt more responsive, like the engine was running better. I thought it could just be my imagination, but I wouldn't be surprised the quality really was noticeable.
 
The main difference between gas companies is the additives they put in the gas. The fuel itself generally comes from the same sources. I have always found that I have better luck with Shell, Chevron, and Mobil, and not so much with Arco or Valero. Cheaper gas stations are also more likely to have improperly maintained fuel holding tanks or pump equipment, which can result in water or dirt getting into the gas.
 
Another difference in gas stations is their storage tanks. About 15 years ago my mother said her 89 Honda Civic wouldn't start. I went to her work and got it running but it was missing real bad, took it out on the interstate and ran it in second gear(auto trans) for about 2 miles. It cleared up somewhat. I ask her if she got gas at this one station that I told her not to buy from and sure enough yes she did. This station must have had a hole in the storage tank because the gas always had water in it. Yes I checked the gas myself and you could see the water separate after sitting. Since then the gas station was remodeled and fitted with new tanks. So if the water table is low in a station area this could happen anywhere. If you live near where gas is stored you could go and see that as others have said most gas comes from the same place except they and different additives.
 
Eric.
Only because its measured on a different scale. You don't have "better" fuel.
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yeah I know, I don't see why it is though, doesn't make sense to me. To make mine comparable to the US I'll go back and edit my post :)
 
Tiddy
I the UK I've noticed that my car runs much better on the petrol I can get from what I'd call actual 'gas' stations as opposed to the ones that are affixed to places like asda/morrisons/etc.
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Following a "discussion" on another forum with a guy who designs engines for a major manufacturer and refuses to believe that supermarket fuel makes any difference because of EU standards and directives, I pulled this from my old, old records:

jumpinjackflash.png

Shell average: 34.21
BP average: 33.47
Esso average: 32.17
Tesco average: 28.24

The driving routes were pretty much standardised. Of course your mileage - literally - may vary and the results are not applicable to anything but the car that the tests were conducted on (my MX-3 V6) - not even to other cars of the same kind with the same engine - but they are reflected in similar behaviour from my other cars.

Tiddy
Talk of 95 as low grade petrol must seem weird though to all of you in the US :p

(All values are UK/EU RON numbers, UK to US values are: (97=92.15), (95=90.25), (99=94.05) )
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They're not quite directly comparable like that, but it's certainly a good ballpark to say 95RON is about the same as 89 octane/AKI, 97 as 93 and 99 as 95. It's not quite true, but feh, how many of us run a car in Europe then export it to the US and run it there? Even the manufacturers don't necessarily make the same cars the same on both continents with regards to fuelling.


For everyone's reference, there are two different ways of measuring petrol/gasoline stability. These are the Research Octane Number (RON) and the Motor Octane Number (MON). Each has a different test cycle - RON, for example, is tested with a "test engine" at 600rpm at various compression ratios, where MON is tested at 900rpm at various ignition timings (also preheating the fuel, as would occur in reality) - and the knock resistance (the tendency to ignite early) compared to iso-octane.

The number equals a knock resistance equal to that percentage of iso-octane in a mixture with heptane, so 95 RON = equivalent to a 95%:5% iso-octane/heptane mix on the RON test cycle. Typically the same fuel run through the MON test cycle will score 10 points lower, so a 95 RON fuel (95:5 iso-octane equivalence on RON cycle) will typically be an 85 MON fuel (85:15 iso-octane equivalence on MON cycle).

In Europe (and Australia, I think. And Japan), fuel is measured on the RON test only and sold on that basis. There are probably laws governing the mix beyond that - I know the EU fuel standards require a minimum MON rating for a given RON rating (but I don't know what it is). In the US they take both the RON and MON ratings and average them out to a third number, called the PON (Pump Octane Number) or AKI (Anti Knock Index) - or, more commonly, just "Octane" - (MON + RON)/2.

So where a European fuel might be 93RON with a minimum (unknown - it'll be in the EU/BS standards) MON rating, a US fuel will have an 89PON rating with, probably, an 84MON and 93RON rating. But since the mixes aren't guaranteed to be the same, a direct comparison is a little moot.
 
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Famine
Following a "discussion" on another forum with a guy who designs engines for a major manufacturer and refuses to believe that supermarket fuel makes any difference because of EU standards and directives, I pulled this from my old, old records:

Shell average: 34.21
BP average: 33.47
Esso average: 32.17
Tesco average: 28.24

The driving routes were pretty much standardised. Of course your mileage - literally - may vary and the results are not applicable to anything but the car that the tests were conducted on (my MX-3 V6) - not even to other cars of the same kind with the same engine - but they are reflected in similar behaviour from my other cars.



They're not quite directly comparable like that, but it's certainly a good ballpark to say 95RON is about the same as 89 octane/AKI, 97 as 93 and 99 as 95. It's not quite true, but feh, how many of us run a car in Europe then export it to the US and run it there? Even the manufacturers don't necessarily make the same cars the same on both continents with regards to fuelling.
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Interesting, so the fuel really is/could be different then between the super market brands and places like shell and esso.

To be honest I've never really looked at actual mileage I've just noticed the car feels different/better depending on where I go for fuel. Some people I speak to seem to agree with me but others tend not to notice, for example I have a friend who swears blind that his '96 mini doesn't run properly if he fills up at a super market petrol station.

The numbers I brought up in regards to the RON/AKI numbers were from a quick google search that told me a rough conversion of RON x0.95 would give me AKI numbers so I didn't expect them to be entirely accurate, it gives a decent indication though.
 
I've edited in an explanation. Bit tl;dr :lol:


The thing with supermarket fuel is that there really is no such thing as supermarket fuel. They get pretty much anything delivered that's cheap at the time and their tanks are filled with all sorts of mixtures. What's under your local Tesco might not be the same as what's under the next Tesco...

Some people will state to the point of insult that it all comes from the same depots so what brand it is is irrelevant. This is true to a point - depots have different areas for different suppliers, so what brand it is is very relevant indeed. The basic petrol has the same basic composition due to the various regional laws and standards guaranteeing that composition, but the manufacturers have their own additives on top of that.
 
87 gas is very inconsistant.
The 91 is much more stablilised between fill ups.
That's why we have to run premium in the karts now, the 87 gas gave too big of tolerances with the gas testers.
Although 91 should burn slower and if you had 87 of the same quality than the 87 would be a bit better for power.
 
What exactly do the additives do? I have always been told that because the additives are in the fuel, you get less actual Petrol...
 
eSZee
If your car is meant to run on 87, run it on 87.
As for differences between brands, yeah, those additive packs really do make a big difference. Shell has been best for my Honda Fit by quite a bit. I get 30-35 more miles per 10 gallons compared to BP/sam's club/thorntons.
Then there's even differences from station to station of the same brand.
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The extra MPG can also be attributed to differences in the way the pumps are calibrated at different stations....
 

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