Watch the deals on here, and get the rebates in.
My last 10 oil changes have been mostly full syn, or semi syn oil for no more than $1-$1.50 per quart, and sometimes even cheaper due to price error or whatever.
The key is to pounce on a deal. I just used up my Pennzoil synpower jugs from a walmart price error, I had 9 jugs.
My latest deal has been the havoline semi syn, it ended up being $1/quart after rebate.
If you have Fleet Farm, they have deals also.
It's been QUITE A WHILE since I spent more than $10-$15 on a complete oil change for any of my vehicles. And I do not use junk oil, all name brand stuff with the latest API spec.