Fouled Plugs- Bad Gas?

[Kolbaso85]

Question for the group. Has anyone had issues with bad gas causing fouled plug?
I have a 2019 GT PP1 with a Roush intake and tune I got from the dealer before delivery. 80% highway driving and only 28,000km. Stored winters in a heated garage but warmed up to operating temperature and taken around the block every 1-2 months during storage and on a tender.
a few weeks ago when I took it for its first fill of the season there was a bit of a stumble and the CEL came on. By the time I got home it was flashing.
Called the dealer and they said better to tow than drive it to the dealer. They ran a diagnostic and I had a misfire on 3 cylinders. They swapped coils, did compression check, checked cam timing and even an oil analysis. All that they could find wrong was fouled plugs that they said must be from bad gas. I was told they were so bad they strongly recommended I don't drive it home to change them myself.
So now I'm out about $800 and I have never heard of bad gas fouling plugs that quickly and easily. I always use 91 or 93/4 octane from a name brand(PetroCan) station.
Has anyone else had a similar issue?

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[DDS]

Have you been using octane boost?

 

[Kolbaso85]

I have not been using octane boost. I only use 91 or 93, whatever the premium is at the station I am at. With my tune they said to run 91.

 

[Postal Bob]

You didn't say whether you used gas stabilizer during the Winter storage. But starting it up, even to operating temperature, and then only driving around the block, will cause condensation to build up within the engine.
Either leave it untouched all winter, or take it for a long, spirited drive, where all engine components will get hot, and burn off any built up condensation.

 

[Kolbaso85]

I don't use stabilizer and I keep my tank relatively empty. The dealer suggested a hard drive as well. I was just surprised that it was so bad that I was shuddering with that little use.

 

[Firsttexan]

I don't use stabilizer and I keep my tank relatively empty. The dealer suggested a hard drive as well. I was just surprised that it was so bad that I was shuddering with that little use.

Isn't it best to keep the tank full during storage? Keeps condensation down. Winter storage is not something we have to deal with down here. Except on our boats.

 

[Kolbaso85]

I was told to keep it low due to the ethanol content now. Fill it with fresh fuel in the spring. Its in a heated garage and its winter so I don't think there is much of a humidity concern. Its usually much drier here in the winter.
What I don't understand is how I went from fine to 3 cylinders misfiring in less than 30 minutes of run time even if it was bad gas.

 

[DDS]

Yes, the ethanol fuel will start to separate after 6 weeks. Shell, Costco and Canadian tire all have 91 with no ethanol. I use that in everything I own, even the weed eater and lawnmowers, never had a carb gumming issue since. There is an app for your phone called Pure Gas, it lists all stations with no ethanol. Shell seems to be the best one, no pinging at all in our old 67 390.

 

[br_an]

There is an app for your phone called Pure Gas

'Pure Gas' was my nickname in college

 

[Qcman17]

I always store my cars with a full tank and fuel stabilizer too. I never start it unless it is going to get at least a 30 minute long drive or more. I would try to avoid ethanol if possible and use a stabilizer too.

I have always been told to fill the tank not keep it low and it’s always been no problem doing that. It sounds like fuel could be the issue to me.

 

[Postal Bob]

I don't use stabilizer and I keep my tank relatively empty.

Exactly opposite of what you're supposed to do. Keep it full right up to the filler neck if possible. And use a good fuel stabilizer in the tank, and take it for a drive, before topping off. This way the stabilized gas is in all the fuel lines. As for stabilizer, I use Stabil Marine formula. It has extra protection against water buildup in ethanol gas.
Keeping the tank empty in a warm garage, then taking it out for a ride in the cold Canadian weather, will immediately cause condensation when the warm gas tank, hits the cold air.
My car sits outside all Winter, on a battery tender, with just a cover on it. It sits from Dec to March/April. I treat the gas just as described, and never start it once. When I'm ready to take it out of winter storage, it starts up immediately. I let it warm up, then take it out for a long drive getting engine and oil temperatures to full operating temps. This way any condensation that might've been in the engine will be burned off. Been doing this for 2 years now, and never a problem

 

[cmxPPL219]

Couldn't agree more with and second Postal Bob's comments.

If folks take nothing else away from Bob and do one thing only, and reiterate, don't just start the car in winter on a warm day, look at the coolant temp gauge (or other gauges if you have them) and think the car is at operating temp by just sitting and idling - it's not. You're doing more harm than good the vast majority of the time.

The engine needs load on it, car needs to be run for a good while, and on highway preferably, a few harder pulls if you want.

 

[cmxPPL219]

You didn't say whether you used gas stabilizer during the Winter storage. But starting it up, even to operating temperature, and then only driving around the block, will cause condensation to build up within the engine.
Either leave it untouched all winter, or take it for a long, spirited drive, where all engine components will get hot, and burn off any built up condensation.

This. Thanks Bob!

 

[Joe B.]

To the OP, no and in your case highly unlikely. Did you check back at the filling station?

 

[Cobra Jet]

So what “tune” did the selling Dealer do to it?

Why would a Service Center tell a Customer not to drive their car due to the condition of the plugs AND tell the Customer to “change them in their own”, while the car is there at the shop being diagnosed???? What?

You paid $800 for what - a Service Center to tell you it needs plugs, but they won’t do the plugs?

What did the plugs look like, any pics, or did they even show you?

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