I agree with post #2. Also, you may be finding out that different oils have different qualities. For instance, a long time ago, in my Omni, I used Quaker State oil. Changed to Pennzoil for some reason, anyway, started having oil pressure issues. Pennzoil had a higher cleaning/detergent capability, and it started loosening all of the crud up inside the engine . Now that took a week or two, not right away. Just be aware about switching oils down the road. I have also heard that going from synthetic to fossil oil is OK, but not the other way around.
