For the record, the last car made that had elastomer compatibility issues with synthetic oils was a Mazda rotary. Since then the seals are better, the oils have to meet seal compatibility test requirements, and the OEMs have upped the elastomer types. No model year Viper falls in the category of needing to watch what oil type is used.
By the way, as the API category has changed from SG to the current SN, so has the base oils. Due to the volatility of all-mineral formulations (i.e. evaporates when hot, gives appearance of oil consumption) better quality mineral oils and synthetic-like mineral oils are used. If you've heard of Group II, II+ and Group III base oils, these are the "newer" versions of what is now called Group I. In the good old days, there were no "Group" designations and mineral oils were mineral oils. There is an extremely high probability that any 5W30 and maybe 10W30 oil today has Group II, Group II+ and maybe Group III base oil in it.
You can't go wrong with the factory fill recommendation. But like a lot of OEM parts, sometimes the decisions are based on costs or marketing. Better oils are (not what you think) those with more additives, not simply better base oils. A synthetic base oil will allow lower and higher temperatures, but at extremes that you would want the engine at. The real performance comes from additives that provide anti-wear, detergency, dispersancy, oxidation protection, corrosion protection, and more. While a gasoline engine oil has enough of these, a diesel engine oil has far more, probably 2X. A higher performance oil would be a mineral diesel oil (I would put this above a synthetic pass car oil) and the "best" oil would be a synthetic diesel oil. Due to the specific nature of diesels in the US, they are really only available in 15W40 mineral and 5W40 synthetic.
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I found Shell Rotella synthetic diesel oil in a 10W30 grade at Walmart. This would be the "fuel economy" version of a diesel oil, but ideal for any pass car and Viper, too.
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A very very worthy alternative is the 0W40 synthetic oils that have European ACEA performance. In Europe half the cars are diesels, so it would have similar high additive treat rates and high protection. It is also factory fill for newer model year Vipers.
Coolants - highly recommend a long-life coolant. The green factory fill coolant is old technology and this is one automotive fluid that has taken a quantum leap forward.
I have a '94 also now with ~109K miles. Enjoy it!
