I have a 98 z28 beefed up some and my wife accidentally put 91 nonethenol in. I have always heard it should make a difference. But went and drove it after she got back and the idle is rough and it's lacking power. Any thoughts on if I should just run the gas through or syphon it out

 

What HAD you been using? A little info goes a long way....

 

I had been running regular 91 premium with ethanol. Here in south dakota can't find 93. When we saw 91 non figured would be better fuel but not sure now

 

Octane ratings are what they are. Your O2 sensors will keep the A/F ratio straight. I wouldn't worry about it.
If it's running crappy you have something else going on.

 

In theory it shouldn't make a difference as the PCM is basing fueling on stoich ratios, and E10 vs. ethanol-free (E0) wouldn't require changing timing. E0 is usually better as it's not hygroscopic like ethanol; and E10 if sitting for long periods, can leave a gummy residue possibly plugging small orifices. However E0 still also has a shelf life and that could be what's happening here. If there's low demand for 91 E0, it could sit in the underground tanks for several months (maybe even more than a year), in which case it's not going to improve until you put in fresh fuel. You may want to siphon out as much as possible, and then dilute the remainder with fresh fuel.

 

Thanks guys. I just found it odd it was running fine til we filled it. I put of vp octaing boost in and drove it and seemed to clean out some not sure if bad gas or what but seems ok now. Appreciate your input