Synthetic or petroleum lube

[98 cobra s/c]

amzoil 5w-30w, when it get's too dirty i change it, but with how few mile's the cobra gets thats about fall anyway's and the car is ready to be put away..... daily's get valvoline dura blend and so far they have been great and start good in the winter....

[Guest]

Is anyone running non-detergent diesel oils like Rotella 15w40? It's suppose to still have the zinc-phosphate (ZDDP) additves that are being phased out of oil cuz it damages CATs or emissions.. Anyone else have any insight on this? Sounds like if your running a roller cam you don't have to worry though. CI4 or CF4 are the ratings to look for if your running a flat tappet cam.

Shell Rotella actually has more detergent for diesel applications which is OK in an already clean engine. Non-detergent is only good for old engines that still have sludge build up to keep it from coming loose. Rotella is supposed to be phasing out ZDDP also. Racing oil have more zinc-phosphate than regular oils but are designed to break down in 1000 miles. I've heard GM EOS additive will add ZDDP, but is no longer being produced? I've also heard STP 4 cyl additive has ZDDP also. As far as synthetic vs. conventional oil goes, syn makes more power and does not break down as fast, but it still gets dirty just as fast and cost more to change. I used to be an oil snob, but now I buy the in house brand at the parts store which is almost always Valvoline in their own bottle.