I buy my Mobil1 at COSTCO & all they carry is the regular full syn stuff. I would guess that there must be a better "cleanning additive package" in the extended life stuff....can't hurt anything and it proly has better sludge control than the regular stuff.
The only thing I try to be sure of is that I buy the full syn stuff...seems there are still some partial sys oils out there, even Mobil has partials.
Tom