A guy at my work with a 2003 ram 3500 with the cummins just told me his current OCI is 20,000 on Rotella 15w40 .... thats CONVENTIONAL!!!
wow!
We have truck drivers load NH3 in our plant everyday!
Most have specialized filtering kits installed on their engines that keep the oil super clean (Filtered) down to a really small micron rating. Similar to Amsoils dual by-pass kit.
These drivers change the filters every 10K miles.
Most run Rotella or Delo 15W-40.
They also run samples every so often!
BUT!
They change their oil every 40K-50K miles.
Granted very little stop/go driving -- Mostly highway / Interstate driving as well as idling.
The oil Never wears out only the additive package gets depleted .
Most of those additives are replaced with makeup Oil.
I do know many of these truck drivers fairly personally and I do talk to them quite rarely about oil as you could imagine.
There are many who visit our plant that have well over 1,000,000 miles some close to 2 million with no major rebuilds in the past using this method so there's no use disputing it works.
If you do attempt to you really make yourself look foolish.
Though these over the road rigs driving habits a far different then your daily driver.
Filtering oil I feel is far more important then most might consider.