Redline is slightly superior to Royal in terms of robustness provided you don't drive your car for short under 10 minute drives. Redline has superior extreme temperature capability (Royal is no slouch mind you, Redline is just a slight bit better). Why? - Redline's formulation doesn't allow burn off of moisture as well until it is fully heated for a while but this is because it's additive package contains more high temperature agents as compared to allowing for that space to contain a higher moisture suspension package. Read - any oil "design" starts with the base stock carrier, the quality of that (which "synthetics" use a superior stock) then the additive packages (which there are many "recipes"). If you take away part of one part of the package, you could add more of another. But in the end, a quart can only have so much of the "additive package" per given quart.
Either Redline or Royal are very superior to ANY off the shelf non-synthetic oil based on the independent "insider" testing research I've looked at. And, as the other poster pointed out, Mobil is probably the best "off the shelf synthetic". Although, they did change their formulation base stock they use as compared to the formulation they offered a few years prior (always chasing those profits).
With the above said though, I actually use Mobil One (less than 30% the price of either Redline or Royal) and keep my intervals
below 7,500 miles. All four of my cars have between 120k and 500k miles and one of them has twin turbos (which can be really hard on oil) yet I have no issue with using Mobil 1 instead of the higher priced alternatives due to the lower change interval.
As to my experience to support the informational review above and "the insider of oil and it's effects on automotive engines" - In my prior career, I was on the inside of the auto industry working directly engine design engineers along with other advance groups as well. One myth that Synthetic oil companies claim to justify their UBER high price is an oil change can now go between 10K and 15K miles. What do the engineers think of this? That this idea of changing oil with over 10,000 miles is ludicrous (at least for long term engine robustness mind you). One primary reason is that gas in this country is VERY dirty indeed. Those blow by deposits of gas get into the oil regardless of what type. And, even the best formulation can only suspend so much dirt. As you approach 10K miles the oil becomes a "dirty carrier agent" instead of acting as a primary "anti-wear" agent
