Oil Change Mix-up

[95E320cab]

Couple of weeks ago I decided to pick up some oil and a filter at Autozone. I use the Castrol Syntec blend, 10W-40 for winter and 20w-50 in summer. This time I let the oil sit in the garage for a few weeks before I got around to changing it. All went well as usual, except as I poured in the last quart, I happened to glance at the jug. It said 5W-30. I looked at the other containers and found four of the seven were 5W-30 and the other three were 20W-50. I remembered when buying the oil there was none on the shelf, so I asked the girl stocking filters to get me the 20W-50. Guess I should have checked her work.

So, the question is, what is the effect of running this oil? I have noticed a decrease in the indicated oil pressure on my gauge. Normally, because I have a bad sending unit, the pressure stays at 3 bar from idle to redline. Now I am down around an indicated 2 bar at idle. Do you forsee any potential risk? I'm at about 83,000 on the odo. Thanks a bunch.

Dave