The most likely cause is water as opposed to a bad mixture. A lot of fuels come from a few suppliers feeding a number of stations. A high use station is your best bet. Their tanks seem to be cleaner from all the constant refilling. There’s no reason to be torn to pieces over this as it’s not a problem. There’s an automotive TV show called Engine Masters. They test engine parts on an engine dynamometer . They tested a number of fuel grades on the same engine and the results were surprising. Less than a 10 HP gain from regular to high test. Using 87 should not be a problem as ANY engine with electronic ignition will compensate for any differences in fuel octane.

I don’t know about Circle K but I’m pretty sure you got a load of crap fuel. 87 to 91 will create a miniscule difference in engine operation. You can’t possibly notice it. And lay off the injector cleaner. Once is enough if at all.

According to the guys on the TV show Engine Masters it makes almost no difference these days with computer controlled ignition systems. They dyno tested regular, premium, high test, Sunoco racing fuel which is 116 octane. There was very very minor changes in torque and HP. Overall HP gain was about 10 on Sunoco racing fuel but it’s prohibitively expensive. The conclusion was if it doesn’t ping regular is fine.

Nope. That water will come back to haunt you. It takes time to do its “work” so stay away.

It’s probably not just rusted out there. Still I doubt if it’s worth a fix.