Post Sandy gas quality
 

After a long search and an even longer wait, I finally found some gas for my z at*a local gas station. *The brand of gas I cannot actually recall, but was definitely not a big chain like sonoco, which I usually use. I told them to fill me up with 91. Shortly after the trip home, my SEL turned on. I immediately checked my gas cap to make sure everything was tightened properly, drove around for a little bit, the light was still on. *The next day I turned on my car, warmed her up for a good 5 min and noticed an unusually high idle rpm. With the car warmed up, the tach read 1000-1100. * This worried me, so I took the car to autozone to check the SEL code. Came back to the dreaded p0300 aka multiple random misfire. My father mentioned earlier that no named brand gasoline companies sometimes dilute their gas with water. This suspicion was confirmed by the gm at autozone. So I purchased some injector cleaner to help remedy the problem.*

This message goes out both as a WARNING and a PLEAto the z community to help diagnose my problem. Keep in mind that I have installed gen 3 intakes along with motordyne exhaust. Untuned. This never threw a SEL for the 6 months I had these parts on. Any comments on what I should do to trouble shoot and or resolve this problem will be appreciated.
Thanks!

Looks like i will keep sticking with my Sunoco 93...

The cheap stations don't deliberately dilute there gas with water (that rumor is as old as gasoline itself) but when the underground storage tanks get old and rusty then water can seep in and mix with the gas. Gasoline is lighter than water so the majority of the water sinks to the bottom of the storage tank, but when supplies run low you are getting stuff from "the bottom of the barrel" so to speak.

Add some stabilizer to the tank top off with some more gas and burn it up and you should be fine.

Cool, thanks for input.
Anyone else have similar issues?
I forgot to mention that this gas probably didn't have ethanol additive since NYS governed abolished requirement for faster gas distribution post-hurricane.

mixed 2 liquids with different densities? woodoo physics?

Water and gas wont mix, so you cant dilute as two layers are formed when combined.
Gas = nonpolar hydrocarbons
Water = polar molecule

Guys, thanks for the chemistry and physics lessons (as if my bioscience major didn't teach me enough of that), but what could be the source of my unusually high idle rpm and SEL. I thinks it's more than a coincidence that the light went on after refueling...

The high idle is a result of the CEL. Certain CEL's put the engine into a failsafe mode with high idle and restricted timing. You can reset the CEL and you might be good for a little while, check for any exhaust leaks near the cats that might throw off O2 sensor readings.

I had similar issues after installing the Stillen G3's in combination with high-flow cats and cat-back exhaust. Once I got a tune everything was good.

Does nobody think this is a result of bad fuel? Lol

Were you using 91 previously or 93?

Ethanol in the fuel can bond with water at a ratio at up to 10%, so with 10% ethanol in the fuel you can end up with 1% water by volume. Seems unlikely if the fuel was being sold quickly but anything is possible.

The other thing that is possible given the situation is that it was actually 87 or 89 octane gas. When you are nearly empty get some fresh fuel elsewhere and reset the CEL and see how it goes.

It _could_ be bad gas, but one event does not establish a trend. ;) Reset everything and see what happens. If you don't get the misfire error again, then it was just coincidence. If the misfire reappears, you have another piece of evidence that the problem is bad gas. I would then check the fuel filter for water and/or trash. Matter of fact, at this point, I'd check the filter just for peace of mind.