[Brian]

Indeed, where I work in a printing company, we have big gearboxes that have removable covers for access/maintenance. these covers [up to roughly 12 foot x 10 foot] are assembled back into place using only a smear of grease on mating surfaces; no gasket whatsoever, the grease alone provides an oil proof seal. Admittedly, the retaining bolts [m8- about 5/16"] that hold covers in place are spaced 3" apart around the entire periphery, but the grease IS the gasket.