I use Aeroshell 15W-50 and rarely need to top it up.
It may be of interest to some that the LW-16702 anti-wear additive required by AD 80-04-03 R2 (Textron Bulletin 446D) for Lycoming 0-320-H, 0-360-E, LO-360-E, TO-360-E and LTO-360-E engines is not required if you use this oil. Apparently the oil has an additive which provides the same anti-wear protection as LW-16702 and the FAA approve this as an alternative method of compliance. Does anyone know what the CAA say about this?