Thicker oil causes pinging, knocking?

[SoulKeeper]

Awhile ago I posted a few messages concerning my 2000 GT making a pinging or knocking noise when I would rev the engine or drive it. I took it to Ford today for the low low price of $89. They told me that the grade of oil I am usig which is Moble 1 10W30 is to thick to be using for that and it could cause the engine to ping or knock. Making the lifters stay up to long. Anyone ever heard of this happening before? I wasnt sure if my 02 Sensors were fried so I unplugged the front 2 and started the car. It wanted to shut off. I have the bypass sensors on the rear. When I plugged them back in, my Check Engine light came on. Why is that? I have had the car for about a year now and when I got it, I put an H-Pipe on it with the Bypass sensors for the rear and the Check Engine light never came on. So why is it on now? Ford told me to use 5W10 oil. If anyone knows of which oil I should be using, please let me know. I pick the car up Fri. evening and changng the oil this weekend. The car was almost 2 months out of warrenty and Ford would NOT fix it or change the oil. Great huh? Any help in this matter would be grealty appricated.