The leaks are indeed from older gaskets where dino oil would plug the microscopic holes becuase the molecule sizes vary... some bigger some smaller.
Synthetic oil has smaller uniform molecule sizes and tends to seep thru older gaskets... it doesn't cause the leaks, just exposes them.
As to getting crap for running Mobil1 or any other synthetic oil... just ignore them.
Yeah it may be overkill for highway driving... but in town driving and in extreme heat/cold it is the best thing going.
Besides you can leave it in for 10K + miles. BMW did a study where they tried all sorts of different driving and testing of the oil.
With Mobil1 the lowest milage they changed was 100% short trips, lots of cold starts... it was 8K miles. The highest was 18K miles, mostly highway and few cold starts.
Other independant studies show that longer drain intervals are a truth and that you can recoop any extra cost by simply extending your drain interval.. heck you could just change your filter every 3K miles if you want the peace of mind.
