Variances in Gas Quality and Octane

SMILEY · Aug 30, 2005

I have always wondered which gas stations carry the best gas. I realize that most of the gas comes from the same refineries and the companies just add their own additives. One day, here in California, I spoke with the owner of a Unocal station regarding the 91 octane premium (Highest Octane available in CA). I noticed that it stated "Minimum rating of at least 91". I asked if the octane was higher at times than the 91. He said yes. He informed me that the octane is tested on occasion and it was at 93 on the last test. That was good info as I have a modified GTP that has a hard time on just the 91 by itself.

So my questions: Is there a listing of octane tests at local gas stations that can be accessible to the public?

What effect do the additives (Techron and V-Power) have on the octane rating? I realize they are a cleaning agent but once you add chemicals it can alter other aspects of the mix.

Rob

k1xv · Sep 4, 2005

I hate to break the news, but octane being much different by brand is a thing of the past. The EPA/CARB so closely dictate gasoline formulas in your area that there isn't much wiggle room on making gas significantly different.

And additives do nothing to the octane of the fuel itself, but a cleaner engine reduces the octane demand of the engine.

SMILEY · Sep 4, 2005

quote:

Originally posted by k1xv:
I hate to break the news, but octane being much different by brand is a thing of the past. The EPA/CARB so closely dictate gasoline formulas in your area that there isn't much wiggle room on making gas significantly different.

And additives do nothing to the octane of the fuel itself, but a cleaner engine reduces the octane demand of the engine.

91 vs. 93 is a big difference for me. Granted, this conversation was 3 years ago. If the EPA/CARB monitors/regulates the fuel what say does it have over maximum octane and what are the tolerance levels? Most importantly, where can I find this information? A link would be great!

I see your from Vermont. I am looking for CA info in particular as our gas (I can almost guarantee) has more crap in it than yours.

Thanks for the info.

wileyE · Sep 4, 2005

I think gas varies so much from one part of the country to the next that to say one brand is better would be hard. It could even change from delivery to delivery at the same station. I've seen the state inspection sticker on the pumps around here and the dates are often 2-3 years old. Not even sure I buy into the "top tier" list, it's probably something you buy on to like "motor trend car of the year". We used to use a vapor pressure tester on our race fuel, I also checked some local pump fuels with it. Results were such that there was no good conclusion, only that "fresh" seemed the best. Fresh super with todays prices may be hard to find? LOL, everyone is finding out there car runs just fine on 87 thank you, at least for the time being.

MolaKule · Sep 5, 2005

Are you asking because you're going to race?

This is a Racing Thread.

Warstud · Sep 6, 2005

quote:

Originally posted by wileyE:
I think gas varies so much from one part of the country to the next that to say one brand is better would be hard. It could even change from delivery to delivery at the same station. I've seen the state inspection sticker on the pumps around here and the dates are often 2-3 years old. Not even sure I buy into the "top tier" list, it's probably something you buy on to like "motor trend car of the year". We used to use a vapor pressure tester on our race fuel, I also checked some local pump fuels with it. Results were such that there was no good conclusion, only that "fresh" seemed the best. Fresh super with todays prices may be hard to find? LOL, everyone is finding out there car runs just fine on 87 thank you, at least for the time being.

This guy thinks so:

http://www.lubedev.com/articles/

SMILEY · Sep 6, 2005

quote:

Originally posted by MolaKule:
Are you asking because you're going to race?

This is a Racing Thread.

Is that why it says RACING ENGINES/CARS?

LOL

Jaybird · Sep 6, 2005

If your motor is not experiencing detonation, there is no need for increased octane.

For throttle response and other reasons, you will never be happy using pump swill in a race engine. Too inconsistent for performance tuning.

SMILEY · Sep 7, 2005

quote:

Originally posted by Jaybird:
If your motor is not experiencing detonation, there is no need for increased octane.

For throttle response and other reasons, you will never be happy using pump swill in a race engine. Too inconsistent for performance tuning.

When I scan at WOT I experience 10 to 11 degrees of timing with about 6 degrees of knock retard (computer pulling timing due to knock via knock sensors). I should be running 15 degrees of timing with no knock retard.

What kind of inconsistencies are you referring to?

CovertRacing · Sep 7, 2005

I think Molekules point was pump gas is not for racing. Get racing fuel.

michael harris · Sep 8, 2005

exactly.. pump gas is for getting there, not for racing. to tune with consistancy, accuracy, and performance use a race fuel. if you decide to go race fuel route and say only need 93 or 94, then bump the compression some to take advantage of the added octane etc.. if ya can get , then get it.
44H

SMILEY · Sep 8, 2005

quote:

Originally posted by CovertRacing:
I think Molekules point was pump gas is not for racing. Get racing fuel.

No. He thought I was posting off topic.

quote:

exactly.. pump gas is for getting there, not for racing. to tune with consistancy, accuracy, and performance use a race fuel. if you decide to go race fuel route and say only need 93 or 94, then bump the compression some to take advantage of the added octane etc.. if ya can get , then get it.
44H

Not exactly. This is a daily driver that is raced on occasion. Race fuel would be ideal but the goal here is to run pump gas. I race on pump gas. If I wanted the extra timing then I could run race gas to get that extra timing. I like to race my car in street trim with no other tweaks so I can see the real world result. The goal here is to find the highest octane rating at the pump. Oh, and I wouldn’t up the compression. Just the boost

It looks like an intercooler is in my future.

Mitch Alsup · Sep 9, 2005

I have used several different barrles of racing fuel all within a very small span of octanes, and tride some self blends. Some of these made more power (+1.5%) on the dynos and some made for better throttle resonce on the track. Not all of the ones that made good power on the dyno had good throttle responce on the track.

One can do their own blending experiments; For example, one can take 91 octane pump swill and increase the octane be adding ethanol, and power will drop and so will milage and throttle response. You can take the same pump swill and add Tolulene and Xylene (ending up with equivalent octane) and both power, throttle response, and milage will increase.

Its not the octane, its the blend.....

SMILEY · Sep 9, 2005

quote:

Originally posted by Mitch Alsup:
I have used several different barrles of racing fuel all within a very small span of octanes, and tride some self blends. Some of these made more power (+1.5%) on the dynos and some made for better throttle resonce on the track. Not all of the ones that made good power on the dyno had good throttle responce on the track.

One can do their own blending experiments; For example, one can take 91 octane pump swill and increase the octane be adding ethanol, and power will drop and so will milage and throttle response. You can take the same pump swill and add Tolulene and Xylene (ending up with equivalent octane) and both power, throttle response, and milage will increase.

Its not the octane, its the blend.....

Thanks for the info. I did not know that ethanol had that effect. Coincidently, I picked up a gallon of Toluene and Acetone. I will be experimenting with 5oz of Acetone with a quart of Toluene for my 17g tank. I will see if it effects the MPG as well as the timing.

I will post back if I find any interesting results.

CovertRacing · Sep 11, 2005

It would be cheaper and better on your engine if you bought racing fuel and mixed it with pump gas.

slugsgomoo · Sep 12, 2005

i agree with covertracing, though it might be a PITA if you are taking your DD on trips, and are unable to find racegas.

I'd be inclined to say that you should look into AVGAS. It's a lighter fuel than racegas, and has less lead than say VP C14/C16, though i think it has as much as Sunoco 110 (though only 100 oct). It's also dirt cheap compared to "true" racegas.

If you have a catalytic converter, get a test pipe before you run too much lead through there though, or you'll be having one verrrrry unhappy feline.

SMILEY · Sep 12, 2005

quote:

Originally posted by slugsgomoo:
i agree with covertracing, though it might be a PITA if you are taking your DD on trips, and are unable to find racegas.

I'd be inclined to say that you should look into AVGAS. It's a lighter fuel than racegas, and has less lead than say VP C14/C16, though i think it has as much as Sunoco 110 (though only 100 oct). It's also dirt cheap compared to "true" racegas.

If you have a catalytic converter, get a test pipe before you run too much lead through there though, or you'll be having one verrrrry unhappy feline.

Dont forget I would be frying my O2 sensors along with the cat.

I agree that race gas is the way to go but its just not practile in my area. It will be easier to just add an intercooler to reduce the need for higher octane. In the mean time I will finish with my little test...

slugsgomoo · Sep 12, 2005

i can get Bosch wideband o2 sensors for $40/ea when not in bulk. I'm not too worried. I've got a buddy who's been running 110 only for the past two years (maybe 8k miles) and still hasn't gone through his first one.

Smiley: what are you driving that is blown, and doesn't have an intercooler?

SMILEY · Sep 13, 2005

quote:

Originally posted by slugsgomoo:
i can get Bosch wideband o2 sensors for $40/ea when not in bulk. I'm not too worried. I've got a buddy who's been running 110 only for the past two years (maybe 8k miles) and still hasn't gone through his first one.

Smiley: what are you driving that is blown, and doesn't have an intercooler?

I have a 1999 Pontiac Grand Prix GTP. It comes factory with an Eaton M-90. Its great off the line but turns into a hot air blower in the high rpms. I have modified it a bit and am putting out around 10 to 11 psi (compaired to 6.5 to 7 psi stock). I have a high flow downpipe, custom CAI, colder plugs and t-stat, 3.4" blower pulley (3.8 is stock), 1.9:1 rocker arms (1.6:1 stock), and a custom programmed PCM.

Bosch's O2 sensors tend to not work well with this car... Im not sure why. Most people end up with poor MPG's and an ofset AF ratio.

Makes me wonder though... if the Bosch's are taking the lead just fine then wouldnt the AC Delco's do just as well?

slugsgomoo · Sep 13, 2005

it probably would, either way, O2 sensors aren't very expensive.

In your case, i'd definitely get an intercooler and get the intake temps down. Do you have any fuel upgrades on the car? Do you have any tuneability other than a custom chip?

I've been using a piggyback (Apex-i AFC) but i'm going to switch to a quasi-standalone (DSMLink) and tie in a PLX-250 wideband so that I can just tune by AFR rather than wasting my time trying to tune with knock count.

Variances in Gas Quality and Octane

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