CARS that aren't regularly driven can develop problems. Seals dry, belts harden, oil drains back into the sump, leaving the engine dry. Running an engine circulates oil through the engine and coolant through the cooling system, but it doesn't help the gearbox or rear axle. It's a good idea to give your car a run once a month. If you can't,, keep the battery on a trickle charger and change the oil regularly.

ADVANCING the timing will exacerbate any pinging. Retard the ignition to eliminate it. LRP has an octane rating of 96, lower than the 98 super the Nissan would have been developed for, so try a 98 fuel. You don't need to add anything to LRP because it already contains upper-cylinder lubricant. On oil consumption, try to identify when the smoke appears. Is it when you start, accelerate, decelerate, or travel at a constant speed? If it's the rings, I would expect smoke to be there most of the time. Otherwise, check valve-stem seals or valve guides for wear.

THE problem may not be with the tail shaft. Have you had your wheels and tyres balanced? Try swapping the front wheels to the back and vice versa. Also check the transmission path the vibration follows to get to where you feel it. There are many components in the path -- suspension bushings, body seals -- that can dampen the vibration and all these should be checked for damage. Also check the alignment of the shaft, and ensure the drive-line angles are within specification.