I do not think Mobil or others have VARNISH DISSOLVING properties sufficient to warrant using them to try to fix a lifter stuck.... fine to change to it after fixing it... but usually 15 minutes at high idle of the Rislone or Barhdol (sp?).... just added to your present oil ( don't overfill though )... will tell you if it is going to work...
I leave it in my engines like 100 miles and then change oil and filter....

Some cars you only have to take the valve action stuff off ... and you can pull the lifters with a little tool... I have done this....

Funny story... or tragic.... my 1964 Lincoln allowed any EXCEPT THE END LIFTERS to be pulled this way... end one bad ? YOU HAD TO PULL THE HEAD !
Bummer.... I got lucky when one of mine stuck... not outside ones....

How much does changing to Mobil One cost ? and filter would be needed also.. then wait 5-10 K will banging the camshaft ? Not a good idea... sorry..