I am having the same issue with my 454 this year. The engine oil doesn't have anything to do with this. In an extreme condition, maybe but not likely in this case. If your engine is well broken in, no reason to run Rotella or any other special engine oil. Due to EPA regulations, oil has to meet minimum specs anyway and for these older loose tolerant engines, and then add some wear on top of that, you're not going to have any issue, no matter what engine oil you use. It's not a tight tolerant engine like LS engines are, so don't be running 5w-30 in it, that's probably or could be to thin. I'd run at bare minimum 10w-40. If it's well worn, I'd probably run SAE 30 or 20w-50. If you want to run the latest hype, you could run 10w-40 High Mileage.
When I got my 454 is was a 30,000 mile Jasper crate engine. I ran some SeaFoam in the gas tank, sucked it into the combustion chambers and then the crankcase. After that, I run Super Tech FULL SYNTHETIC 10w-30 and a Mobil 1 or K&N filter. I change the oil once a year (12-15 months to be exact) or 10,000 miles whichever comes first. I've probably got about 8,000 miles on the current oil and I'll assure you, it's still golden clean oil that will look as new as most conventional grades of oil does right out of the bottle. It's a very clean engine, and it stays that way. This BS of changing your oil every 3000 miles is just that, it's ********. In my K1500 with a 10,000 mile crate 350 in it, I ran conventional 10w-40 Super Tech and a Wix Gold Filter. Changed it about 5000-6000 miles and gave it to my bro to burn in his oil burning ricer since it was still dark golden when I changed it. How often you change your oil isn't near as important as how clean you keep your engine. Motor Oil NEVER wears out. It last's forever. What does happen to it and why we need to change it, is because it gets dirty and it gets diluted. Diluted by combustion gasses and water from condensation in the oil pan. Obviously my engines are in good shape, and combustion gasses obviously don't get past the valve guides or rings as of yet or the oil wouldn't still be as clean as it is after 8000-10,000 miles. If it's clean, not dirty, not diluted, no reason to change it. If I keep it this clean, it helps keep the wear down too. There's probably 60,000-70,000 miles on the 454 now and it's still clean as can be oil and not a bit of smoke out the tailpipe, and no blow by. I hope to keep it that way.
Sooooo moving on, fan clutch has already been mentioned and is the 1st thing likely to be the problem. In my case, mine is running about 215 when I'm in traffic. Get moving it's back to about 185. Fan clutch seems fine. I replaced the water pump not long ago and it had some white calcium looking junk in the old one built up in the corners. I have a feeling the same **** is in my radiator and I probably need to flush the radiator and hope that helps since I'm not aware of radiator shop I can take it to to have it rodded out and cleaned. Coolant level is fine, recovery bottle system is working perfect as in recovering coolant when hot and sucking it back in as it cools, but it still runs 210-215. Do keep in mind, Big Blocks are cold natured when first starting, and they also tend to run hotter. This is due to all the heavy cast iron in the heads.
