When I put my '15 GT away for the winter, do I fill her up before storing her in my garage?

 

Yes. A full tank prevents condensation, or so I've been told. At the very least that's one less thing you have do after the thaw so you can just jump in and drive 'er.

 

A full tank means less moisture from the air in the tank, hence less corrosion risk.

 

Don't forget the STA-BIL (storage type). Run the engine a bit with it in there to get it throughout the entire fuel system. Keeps the fuel fresh all winter and you'll be set to go in the Spring.
In the Spring add a bottle of HEET (red bottle about $3.00) to suck up any moisture, even with a full tank of gas in there. I've done this ritual for my 'collector' cars for many years.

 

Do you think that's necessary if the car is run regularly during the winter? Once the snow/salt/slush hits the roads mine's in the garage but I run it once or twice a week for 20 minutes each time.

Opinion?

 

Running it can cause more harm than good. Moisture forms in the crankcase and you never get the oil hot enough to boil off the moisture.

 

Yes, still do. I also run my AMC (and a Chevy before that) for 30 minute runs during the winter (actual drives, not idling which is bad). I don't put enough gas in there over a 4 month period to use it all up. The Sta-bil keeps it fresh and the HEET will suck up any moisture that accumulated in the tank.
As an example: I would run my Trans Am all winter but usually short 20 minute grocery trips. The moisture accumulated in the full tank (didn't realize it) from the exhaust heating up that cold gas tank numerous times. On a trip to Florida I started sucking that moisture right in, causing misfiring. Two cans of HEET dried it all up and it has become my standard procedure in all my cars since. Never had an issue again using just one bottle every so often. I get 4 packs of the stuff from Walmart for around $2 per bottle. It's $3 at the auto parts stores. I get the red bottle (vs yellow) as it also contains a 'cleaner' which certainly doesn't hurt.

 

Put mine away beginning of November.
Fill her up, add some fuel stabilizer, put on a good battery tender, cover if needed.
No need to run until she's out for the long haul

 

It's always good to fill her up before putting her in storage.