I'm glad the Mobil 20k topic came up. I've noticed the ads, and have many questions about this. First and foremost, who will guarantee it? Will GM support 20k miles between changes? If there's any engine failure due to using tired oil, will Mobil pay for a new motor? Will the other oil makers follow suit?
There already appears to be a trend towards longer life oils - it seems the lube guys are all steering towards synthetics as their mainstream products. I think OEM requirements such as Dexos are driving them that way. But 20k miles? Wow!
And who here wants to find out the hard way that GM is not in line with Mobil's claim?
I assume that, besides cleaner burning engines, another benefit of electronic fuel management is longer oil life. I've seen that trend in recent years with the oil life monitor systems calling for oil change intervals which average around 6000 miles, twice the 3000 miles of yore. But 20k is a quantum leap beyond 6k.
And, besides the lube makers and the car makers, where are the filter makers on this topic? Are their filters up to the task?
When I hear the 20k claim in the ads, I cannot help wondering how Mobil can back that up. In order for them to declare that, it seems lots of other players have to be in alignment.
Lastly, if someone's engine did fail due to the oil not lasting 20k miles, how does that show up in the tear down? That is, what other engine issues - eg, coolant leaking into the crankcase, using the wrong oil filter, stuck rings - can leave similar scars as oil failure? What might prevent the blame from being placed somewhere other than oil failure, resulting in the car owner being stuck with a dead motor and no warranty?
20k miles is an extraordinarily bold claim. But my instinct is to proceed with caution - lots of caution. Oil changes are still way cheaper than new engines.