I watched a 60 Minutes episode a few years back where Consumer Reports took 10 New York City taxi engines apart, inspected, photographed and documented engine wear then rebuilt the engines. They placed new motor oil in all 10 taxis. 5 taxis had oil changes every 3,000 miles or every 3 months for one year. The other 5 taxis also got new oil but went a year with no oil change, only weekly level checks and filled to proper level.

After the year was over all 10 of the engines were torn apart, reinspected and no difference was found in engine wear between the two groups.

Something to think about...