winter oil thickness and my poor car :(

[Yoshi]

okay guys, this is painful for me to say, but here goes.
in the past week or so temp has been fluctuating A LOT. You have to understand that where I live, temp can change as much as 60degrees over a 12 hr period, its nuts.

My car currently has 20w50 in it, which was fine and great (redtop)... this morning winter offcially hit, it was 45 yesterday evening, and when i got up, it was 17degrees. I had no choice but to drive my car to work, I think the oil is way too thick and can't handle the cold. I had a very bad feeling, but I was late as it was, so off i went.

Now my car stutters above 4k or so, and I boost is all over the place I haven't had time to go back out and check for pipe leaks or BOV leaks for the boost, but I'm really worried. I think I'm going to get some 5w30 during my lunch break... but someone please tell me I didn't severely screw something up!

I'm in the middle of the "oh sh|t-what-if-my-engine-is-fux0r'd" panic stage, since I can't go play with it