That's true, Critic. As I've told tig1 before, I'm a skeptic at heart and tend to use a lot of conventional at manufacturers' recommended intervals (except the taxis, which were significantly extended on conventional, but which were good candidates for a variety of reasons). Nonetheless, we see very few UOAs here where a synthetic isn't acceptable for an extended OCI (assuming the engine was speced for conventional in the first place).
Yes, I'd be very shaky taking M1 to 10,000 miles, but that's an emotional response, and a skeptical response. I've seen that it can be done through UOAs. Tig1 has done it for a long time with nary an engine explosion.
Let's take one thing - M1's warranty - and see what we can draw from that. One possibility is that XOM is telling the truth. Their oil can go that long in almost every application, or at least enough applications that they're willing to guarantee it.
Few, if any, other oil companies offer such a warranty. So, that brings up other possibilities. XOM says I could use EP in my car for 15,000 miles. SOPUS says I could use PU for only 3,750 miles. So, either SOPUS is being very conservative or XOM is making a far superior product to everyone else on the planet. I'd believe the former, first.
Also note that those applications where we've seen significantly extended OCIs across the board tend to require synthetics. The Germans moved to synthetics for a couple reasons, and a significant reason was that their OCIs were overly optimistic for the specified conventional. Instead of reducing OCIs, they actually lengthened them and introduced their own specifications. Look at what Doug Hillary accomplishes in his fleet with synthetics.
And we can never ignore cost. If I'm spending double the money on a product, I want my ROI to make it worth it. And, regardless of any sales, synthetic up here is double the price of conventional. I know people can cherry pick PP or Synpower rolled back to $19.99 at WM or NAPA and compare that to the gas station's $32 jug of PYB, but that's nonsense. Certainly, there are extreme cold and extreme heat benefits to synthetics and a better additive package. But let's be realistic. I live in a place that can have some of the world's coldest and hottest temperatures. I haven't had issues using 5w30 conventional in -40 C. And I haven't had engines heat themselves to the seizure point in +40 C on conventional, either.
But, I do understand your point, and I'm jittery, despite all the evidence and my own experiences. I'm not afraid to admit that I'm very, very likely wrong in my skepticism, and if I were so inclined, I could likely prove it to myself by trying it and backing it up with my own UOAs. But, I know you're very meticulous with your maintenance, as am I.
Then again, so is tig1, but he still does 10,000 mile OCIs on M1.
My dad would have been proud of him. If I did 6,000 mile OCIs on synthetic, much less 3,750 mile OCIs on it, he'd have told me I was nuts.
