Please help me understand Extended Oil Drain motor oils

[Cary]

You are not doing 15k, you are doing 10k. There is a significant difference.
And I am very happy to hear about your positive experience! Seriously, that is great. But not everyone will have the same result.
$1500 over 20 years time is a relatively small expense when the owner values long-term reliability. Speaking in generalities, not your particular circumstances

Agree there is a big difference between 10k and 15k. I went 10k in the Land Cruiser based on my UOAs and those of others on the same engine. I suggested to the OP, sampling every 2,500 miles after 10k to establish when the oil starts to fail. I would recommend the same to anyone exceeding factory intervals and even then build in a bit of cushion (i.e. oil hits the used up point at 17.5k, run 15k intervals). I believe in maximizing value, but not being penny wise and pound foolish.

 

[NO2]

An NA engine with mostly highway miles should have no problem running 15K with extended life oil as long as you have a high quality filter. Running that same engine in stop and go conditions should have much more frequent oil changes. That's around the OCI we run, and we add oil as needed (2Q over the interval with a Subaru 2.5 FB).

We are sticking with 6K OCI with our DI Subaru.

 

[ChrisD46]

I'll just part the thread by mentioning that I believe what I can see or experience myself ...... so when I check my cheap used 10w30 oil & filter after 3K miles ...... it appears black .... it smells bad and contaminated .... and the filter appears full of crap.
And my crappy 3.8L Korean engine does'nt identify a difference in the bundle of different viscosity oils either after 220K miles so far.
Gullible folks are what keeps the economy humming.

So , what does your 3.8L engine identify as ? What pronouns does it prefer ? … My 2.4L Theta II GDI engine identifies as an oil thrasher and oil diluter . Preferred pronouns are : It , They and Needs Oil Added .

 

[SARG52]

Rule # 13 applies