...it does not smoke upon start up or while driving....
...checked the plugs and all of them were oil fouled....
These two statements are contradictory.
If the spark plugs are oil fouled, the engine is burning oil and should be anticipated to emit bluish gray smoke from its exhaust, though it might be slight and difficult to observe. A momentary bluish puff of smoke at cold startup indicates worn valve guides and/or valve guide seals - bluish smoke under acceleration and cruise is more consistent with piston ring wear/damage, cylinder glazing or oil dilution.
Allow a drop of engine oil to fall onto your clean fingertip from the dipstick. Does the oil hold together in a tight, well-defined circle or does it quickly track outward along your fingerprint? Tracking your fingerprint indicates fuel dilution of the oil that can easily pump past the piston rings. Fuel dilution can result from a faulty mechanical fuel pump or prolonged fuel leakage from the carburetor directly into the intake manifold. You can perform a dry/wet compression test, or better under the circumstances, a cylinder leak down test to determine cylinder condition.
1
