My '99 V10 lived most of its life on dino 5w-30, and based on the amount of heavy varnish I could see in the valve cover - I suspect it did not have the oil changed as often as it should have. I purchased it with 80,000 miles, and have run synthetic oil in it ever since. It seems to do fine on 5w-30, but I did notice reduced oil consumption the few summers I ran 5W-40 HDEO.
Mine had the same exhaust manifold issues mentioned above. I had both sides replaced with Dorman manifolds, which have held up well. The only other problem I have had with the engine was the harmonic balancer. The rubber dried out, and the outer ring got loose enough to move forward and hit the fan. Thankfully it just barely touched the fan and I got it shutdown without disaster.
Mine had the same exhaust manifold issues mentioned above. I had both sides replaced with Dorman manifolds, which have held up well. The only other problem I have had with the engine was the harmonic balancer. The rubber dried out, and the outer ring got loose enough to move forward and hit the fan. Thankfully it just barely touched the fan and I got it shutdown without disaster.
