Hello Mate,
As you probably know the oil pressure senders fail at the same time as the tension rod bushes on the Z32 i.e every 10,000 miles. There was someone on the 300zx forum who was trying to fix the faults with the sender unit but can't remember who it was. Anyway people I have come acroos, scuse a bottle of wine affects my spelling, have the best results changing the oil every 3K with Mobil1 15-50, CastrolRS 10-60 synthetic or redline synthetic oil. I have used Mobil1 15-50 bigger halfords do it, and the results are great the engine runs beautifully and quietly. By the way national autocare are doing synthetic oil+filter changes on 200sx for £20, if you tell em it's a 200 sx they don't know and I think the oil filter is the same don't quote me on it though, too much wine has blurred my oil filter memory.
Mark