Pretty much the title. I need to make some hard lines to go from the oil tank to the front of my stock car. I technically could mig weld aluminum with the welder I have, but steel is much easier and cheaper. If I made hard lines out of steel tube and welded steel AN bungs to the ends, would it be a terrible thing to mate them to the aluminum fittings on the hoses?
Totally fine.
Depending on tube thickness, you may be able to just put a tube nut and sleeve on it, flaring the tube directly, then attach to a bulkhead fitting. That reduces the Colander Effect of welded high pressure fittings, and the bulkhead connector gives you a way to solidly attach the connection so it doesn't vibrate the snot out of the hardline.
They will seal up fine but may be vulnerable to galvanic corrosion in the long term, be sure to oil the fittings to avoid that.
Awesome, that's good news, thanks! What is the Colander Effect?
In reply to AMiataCalledSteve :
That is when your patched together welds hold liquids as well as a colander 
In reply to Pete. (l33t FS) :
Lolol
In reply to GameboyRMH :
They are also vulnerable to effects of thermal expansion and contraction.
Yeah I wouldnt weld a fitting to a tube. Flare it and use a sleeve and tube nut and the bulkhead fittings. They also make compression fittings. For an oil cooler I would want steel lines due to the burst strength/pressure rating. Dont want a reverse Titan situation.
In reply to 93gsxturbo :
You need steel for PS systems that run 4-5 digit PSI, but for oil coolers in the low 3-digits aluminum is fine, remember that the cooler is made of fairly thin aluminum.
In reply to GameboyRMH :
And air conditioning systems run thin aluminum lines and aluminum condensors and run pressures up to 450psi before safety blowoff.
One of the Old Farts on Nopistons used to talk about TIG welding AN fittings on 70s GM evaporator cores for use as a cheap racing oil cooler. They see up to 130-140psi inside the cabin on a hot day when the system is off, so they handle the pressure. I'd trust a TIG welded fitting over MIG, having MIG welded fuel rails before.
I've welded steel fittings to steel lines and connected aluminum hose ends to them a bunch of times. Mostly in power steering systems but occasionally on oil likes like OP is asking about.
I would see if you can find someone to TiG them for you.....that's what I did with my fuel lines for my Mini project.
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