What type of antifreeze should be used for a 2001 subaru outback

My advice is go to your local Subaru dealership and purchase the fluid or have it changed there. Also, be sure that you only use a genuine original thermostat , radiator and water pump for your Subaru. They're specially designed for this car.

Only go to a Subaru dealer if you want to pay way too much for service. Any competent mechanic can take care of your Subaru's cooling system. Do use Subaru Anti-Leak in the radiator!

I installed an after market radiator and water pump in my 2003 Forester and they worked great and never had a single problem with them and saved a ton of money over Subaru prices.

ATM and Grasshopper (Mark) are wrong again. You CAN intermix red and green, and don't sweat it. The older additive dealers poured into the radiators for $8 was just an attempt to prevent HG failures. It didn't work. Mark's correct in learning from me that the OEM LARGE ORIFICE t-stat is required; but since the originals NEVER fail, don't even bother to remove the original UNLESS you've clogged the system with oatmeal or fishmeal sealers. Sourcing the rad or water pump (also almost never needed!) is easy, and does NOT require OE sourcing. So FOR is correct again. On a 2000+ OB it's hard to drain the rad unless pulling off the t- stat cover or its hose clamp. If the former, ensure the 0-ring seats nicely when you bolt the cover back on.. If you find that the t-stat and its o-ring pop off with the hose/cover, then be careful not to splash yourself with tumbling hot coolant. If you've ruined the 0- ring be sure to use a new one...but again the t-stat is always good if OE and should be reused. Your rad is probably ok unless the front lower half is externally blocked by mud, leaves, sand, etc; spray-cleaning usually works. If rad is internally blocked...or cracked from age and past overheating just chase a generic cheapy. They're all fine.... Subie's cooling system is robust as long as it's kept full, as, after all, it also is used for the 50% larger 6 cyl motor successfully. So don't sweat the coolant. Just make sure you fill the top rad hose (burping all air out of the system) and then the outer expansion tank. Note that parking with the front raised helps purge any trapped air from the rear heater core hoses too. It's not rocket science, and doesn't require a dealer.

Just saw FOR's additive note. SOA rad additive is just a red-tinted version of premixed, cheaper Bar's Leaks. ..for twice the price for half a bottle! That said, 3-5 oz of Bar's Leaks can take care of MINOR hose clamp, waterpump seal, etc leaks, but will NOT repair nor prevent head gasket failure. So many of us wish that it had...!

The SOA additive does not look like Bar's leak to me but I will take your word for it but I think it is only $3 on Amazon. I used the Subaru stuff and once Alumaseal and got 200,000 on my original head gaskets. I was loosing a small amount of coolant (maybe a quart or two a year) and the additive did slow it down a lot.

You got lucky. BL is available both as the original coarse pellets AND pre-shaken in a gravy-like pour that's like the SOA red one. It MAY help slightly in slowing a coolant leak at #4 cyl, but of course the subsequent oil leak on the right head will prevail, necessitating replacing the gaskets anyway.

The stuff I used must have been the pre-shaken stuff. In any case the car was running like new when I sold it at 200k. There was a slight oil leak but it never left a spot on my garage floor.

Haven't used Alumaseal in decades. Pro mechanic said that he stooped up a few Subies with the newer annoying multi-step sealer ($30) from Bar's Leaks, but I've not heard from any other trusted sources that it works at all. Bar's now has an even newer One-Step HG sealer that appears to me a fine copper powder dispersion in a pourable glop. May be useful for minor peripheral leaks,but I've never found ANY additive prevented the older gaskets from opening up. I remember someone complaining that Alumaseal also clogged fine passages, but not as badly as the tan oatmeal sealers.

All I can say is Alumamseal has worked for me over the years without any unwanted side effects. It seems like the lesser of evils when compared to all the other stuff.