Motor Oil

I change my own oil.  I have a 2003 GMC Sierra with 5.3 liter V8 with 106,000 miles.  I use synthetic oil started using it from new.  Last night I changed oil.  Engine takes 6 quarts.  Dumped in one 5 qt container and one single quart container.  When I was finished I discovered I had mistakenly bought a 5 quart contianer of 5-20 oil.  Consequently I put in one quart of 5-30 and 5 quarts of 5-20 oil.  Manual recommends 5-30 oil.  I hate to drain out $35 worth of brand new oil.  Should I be concerned with 1) mixing viscosities, 2) Using 5-20, too light?  Hate to waste the money but would still be a lot cheaper than engine trouble.  

no problem,it is a little thin,but no damage to engine.  

106,000 miles on a 2003, you must drive everywhere in your sierra. What kind of motor oil do you use? My car is up there too and I use Pennzoil, is that a good oil or should I switch.  

50 mile round trip to work each day before anything extra it adds up.  I'm not loyal to any given brand of oil although I do not use the "no-name"brands.  I pick which ever name brand, Valvoline, Mobil 1, Pennzoil etc. in full-synth, that is cheapest at the time.  I'm  believer in the synth oil though... this is the third vehicle I've used it in and have never had a problem...in this day and age however, you don't even change spark-plugs until 100,000 miles so I guess I shouldn't have a problem regardless of the oil.  

Pennzoil not my #1 choice I have had engines come to me for rebuilding that used pennzoil all there life and they were sludged up pretty bad.  

Bill I feel for you on how miles add up. I do a 80 mile round trip to work and the miles add up quick.

Pontiacman8 what are your opinions on Castrol Motor Oil; just wondering because thats what I use for my daily driver?  

Both castrol GTX and valvoline are what I use they are good oils.  

i think gm uses castrol gtx but valvoline is very good but personally i use royal purple  

I would use royal purple if I could afford it; how much does a quart cost?  

Royal purple is not all its cracked up to be.  I've see lots of evidence online of it wearing down metal.  Ever heard of Schaeffer's oil?  They're a word of mouth brand.  There stuff is #1.  I think richard petty in nascar used it.  Also Pennzoil Platinum is what the "oil guys," on ls1tech and ls1.com say.  I use PennPlat because it's easy to find and works WELL.  I was having a problem with burning oil with quaker state, mobil 1, schaeffer's, but PennPlatt is easy to find and I think the best from the way my car doesn't burn oil any more.  Some of these guys get a sample of their oil and send it off to labs and they send back results telling what all they found inside the oil.  It is a very fine and complex print out they get.  BUT PennPlat(pp) is the best.  get it at walmart for like $23/5qt.  GOOD STUFF!  
http://www.fquick.com/garages/viewvehicle.php?id=8666

NO I haven't but all I used in my high performance engines is valvoline 40wt and lucas oil stabilizer.