Royal Purple vs. Mobil 1 Oil Analysis

In the field of commercial motor oils, there's a longstanding rivalry between synthetic brands Mobil 1 and Royal Purple. To the brand loyalists, the competition is every bit as fierce as Ford vs. Chevy, Coke against Pepsi or (locally) Alabama opposed to Auburn. Additionally, advocates of each brand feel compelled to dole out unsolicited advice when they see you buying the offending brand. Recently, when I bought six quarts of Royal Purple at my local Advance Auto, I was practically interrogated by the sales clerk who ended the conversation by succinctly stating, "You should have bought Mobil 1" even though he could present no compelling evidence it was better.     

Although my Ion Red Line came from the factory with Mobil 1 5w-30 in the crankcase, I was persuaded to try the purple stuff by friends, co-workers and in-laws who purportedly gained fuel economy and horsepower just by switching to Royal Purple. Unfortunately, these results were not substantiated by dyno reports and no two engines respond exactly the same. 

The biggest difference I've noticed between RP and M1 is the price. A 5-quart jug of Mobil 1 can usually be found at Wal-Mart for around $25 and it typically goes on sale elsewhere. A current promotion at Advance Auto has 5 quarts and a Mobil 1 oil filter for just $29.99, a savings of more than $20 off their retail prices. Royal Purple, on the other hand, is about as rare as Kobe Beef and just as expensive. It never goes on sale and retailers who do carry it, don't budge off the price which is close to $10 per quart. In essence, I wanted to determine if Royal Purple was worth twice the cost of Mobil 1.

So I figured the best way to settle the dispute was to obtain samples of both Mobil 1 and Royal Purple from my engine after 5,000 miles of use. While it wouldn't conclusively demonstrate a gain or loss of horsepower (a dyno would be needed for that), it would illustrate which provided more protection from engine wear. I had already debunked Royal Purple's alleged increase in fuel economy as after 5,000 miles I hadn't come close to exceeding my all-time high set in July 2011 with Mobil 1. 

One of the criteria Blackstone sets for its used oil samples is that they prefer it come immediately from an engine that has been properly warmed up. Typically, this can be achieved through thirty-minutes of highway driving which helps burn off any moisture and other particulates which might skew the findings. This sounds easy and convenient on paper, but in reality means exposing tender bodyparts to various hot exhaust pieces that can exceed 800 degrees. Furthermore, with the RL on jackstands in my yard and only a couple inches of clearance, it really makes things interesting. Suffice it to say, after two separate oil samples from my car and one from my wife's Ford Freestyle, I'm glad I won't be needing to gather any more in the near future.

I shipped the sample on Monday and by Friday afternoon had the results in my email inbox. While Mobil1 doesn't acknowledge any specific properties in its synthetic oil, Royal Purple likes to point out its patented Synerlec additive which utilizes high concentrations of zinc and phosphorus as anti-wear additives. When guys stand around and toss out the old adage, "They don't build them like they used to", it could very easily relate to today's fancy motor oils.  Tightening emissions requirements are primarily responsible for squeezing zinc almost completely out of new motor oils. The American Petroleum Institute (API) has continuously cut the amount of zinc down to just .08 percent, from .15 a few years ago, and even higher than that in the early '90s.  Royal Purple's Synerlec attempts to correct this by adding more zinc and phosphorous than currently allowed by API-certified oils. They also point out that this should not be used by newer cars still under factory warranty due to potential problems.

The higher levels of zinc and phosphorus are present in the findings below, but surprisingly didn't seem to really help. The flashpoint is also lower in the Royal Purple sample which is not desirable, although in all fairness it is slightly above the minimum value. But the big news is the Total Base Number (TBN) which determines the remaining acid-neutralizing effectiveness of the oil after 5,000 miles. Royal Purple scored a commendable 6.1 but the Mobil 1 sample was nearly 15% higher with a 6.9 TBN.

Disappointingly, the conclusion based on these results is that Mobil 1 is the obvious winner. It clearly provides better protection at half the cost. I had honestly hoped for a better showing with Royal Purple but it wasn't in the cards. It looks like my next oil change will be with Mobil 1.