Seems like about 25 to 30 years ago Consumer’s Reports magazine tried to evaluate motor oils by having engines rebuilt by the same company, then running motor oils in those engines for 1500 miles change out periods in Taxi Cabs service in New York City. After 1000,000 miles of service the rebuilt engines were torn down and wear parts were measured. Consumer’s Reports wrote that this method “failed” because they could not measure “statistically significant” differences in the dimensions of the wearing parts versus new.

But to me the most interesting part of that long ago CR report
was that some taxi cab companies in New York City had a long term policy of changing conventional motor oil at 500 miles,
and claimed that they could prove by their records that it was cost effective in the long run.
This was before synthetic oils were widespread.

I wonder if any NYC Taxi companies still use conventional oil and change it at 500 miles?

I know in the mid 1990s there were big 18 wheeler trucking companies that claimed that
non-synthetic Shell Rotella changed frequently was doing better than synthetic oils run longer.

Today overnight radio stations run synthetic Shell Rotella ads about every 20 minutes all night.