Lifter problems????

superdart said

I recently changed from Castrol SAE30 to Amsoil 10W40 motor oil in the car. I waited over 1000 well driven miles before changing. A few weeks later I developed a tapping noise at startup if the car sat more than a day. I don't see how going to a heavier oil would cause anything, but I thought I'd put it out there.

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Doesn't answer or maybe it does but anyway. 10w40 is a lighter weight oil at start-up temperature than straight 30W. The 10W40 designation means that the oil pours the same at 0 degrees as 10 weight and will not thin out more than more than 40 weight at 2xx degrees. Also, the general concensus is you don't change over to synthetic oil until you have 5-10k miles on the engine.

Also, there has been lots of discussion lately about modern oils not having enough of the anti-scuff additives required to protect flat tappet cams. The zinc that used to be added to oil for scuff protection has been mostly removed for emissions purposes. Because virtually all new engines have roller cams an do not require the protection an alternative was not added. Worest case you may have the beginnings of a wiped cam.

Before going to wild, check the obvious things you mentioned. You also might want to switch to a deisel oil like Shell Rotella T 15W-40 or 20W-50 which still does have the additives. Also, a different oil filter, one with a better anti-drain back valve may be worth a try too.