I have a Lincoln Weld-Pak 155 wire feed welder (220 vac) that I plan on using for some panel repairs. What type of gas and wire size do you use for sheet metal.

Argon mix.

Is that the 80/20 mix? Argon/CO2

I use a deal called steelmix from airgas its 83/17 ar/co2, IIRC. You could use a standard 75/25 mix as well.

I prefer to use .023 wire when doing sheetmetal.

.023 wire and standard mig mix works well for me.

Thanks to all.
I just checked out the cost of bottles and gas, they ain't giving it away.

Argon Mix 75/25
80 - $206 + $45 Fill
125 - $224 + $49 Fill

Oxygen
155 - $240 + $30 Fill

Acetylene
#4 - $260 + $63 Fill

Is that lease or purchase?

Purchase. Lease is about $100 per year per cylinder + gas.

That is not bad prices.

75/25 Argon/Co2 with Lincoln Super Arc L-56 ER70-S6 works really well on sheet metal, header tubing etc.

For heavier stuff I do straight Co2 with Lincoln SuperGlide, but that's really hard to find. I order 44 lb. ready reals, usually 5 at a time in order to get it brought in.

how big are those bottles? how much are you going to use them? I have tiny little bottles for my oxy/acetyln set-up, bottles are about 18" tall and 6" diameter. Had them for about 2 years now, and I'm still on my first set. I think the price was like $150 per bottle, and $20-30 to exchange them for full bottles. they won't fill your old ones, only exchange them.

I located a used argon tank, it is about 48" tall. The owner is asking $100.
From what I understand, when you buy a new tank, you lose it on the first refill. Assuming you actually receive a new tank in the first place.

I leased a tank on a 3-year lease for 30 bucks a year and 75 per fill. I can't remember what size it is off hand but it stands probably around 3 feet tall I think. Maybe a 60lb tank, I can't remember. I just remember looking into buying and if you buy you lose your tank on the first fill when you trade it in for a full one. They only wanted to sell real small ones, smaller than the one I got, maybe 1/2 or 2/3 the size, wanted way too much for the bottles and not a cheap rate when refill time comes either. I thought mine was a bit too much for what I paid but at least there's a dealer for them 5 minutes away from my house so swapping tanks out doesn't have to be a big deal.

And I also went with the co2/argon mix. It works well but when welding from the bottom I find the weld pool tends to want to blob and drip down. I heard that straight c02 doesn't do that so much. But if I start and stop as I'm doing my bead it's still very manageable to do from underneath.