For consistency, we used only 1992-93 Chevrolet Caprice cabs. Each received
a precisely rebuilt 4.3-liter V6 at the beginning of its 60,000-mile test.
We started with six rebuilt engines; after each engine was installed in a
cab, the six engines that were removed were rebuilt and installed in six
other cabs-and so on. Using that rotation, we monitored 75 cabs over 4-1/2
million miles of driving in New York City and its environs. Each oil was
tested in three engines.
A local shop completely machined each engine block and crankshaft, rebuilt
the cylinder heads, and installed new bearings, pistons, rings, seals,
gaskets, and oil pump. Though the engines originally had roller lifters and
camshafts, a design that reduces friction, we installed conventional sliding
lifters and camshafts to accelerate wear.

Before the engines were assembled, we measured or weighed the parts most
likely to show wear if the oil wasn't doing its job - the camshafts, valve
lifters, and connecting-rod bearings. Each cab went through a break-in
procedure before hitting the road. During testing, two engine timers
measured the time the engine was running and the time it was in gear.

Over the next 22 months, our engineers paid more than 100 calls - usually
without notice - on the fleet garage. They dropped off test oil and picked
up used-oil samples for ongoing analysis. They also made sure that oil was
being added to the engines when necessary and changed as scheduled.

After each 60,000-mile test, we remeasured the key engine parts. We also
examined combustion-chamber deposits, the color of the valves, scoring of
cylinder walls, and valve-deck deposits for any sign of engine problems.

After each engine ran about 60,000 miles (and through 10 months of seasonal
changes), we disassembled it and measured the wear on the camshaft, valve
lifters, and connecting-rod bearings. We used a tool precise to within
0.00001 inch to measure wear on the key surfaces of the camshaft, and a tool
precise to within 0.0001 inch on the valve lifters. The combined wear for
both parts averaged only 0.0026 inch, about the thickness of this magazine
page. Generally, we noted as much variation between engines using the same
oil as between those using different oils. Even the engines with the most
wear didn't reach a level where we could detect operational problems.

We measured wear on connecting rod bearings by weighing them to the nearest
0.0001 gram. Wear on the key surface of each bearing averaged 0.240 gram -
about the weight of seven staples. Again, all the tested oils provided
adequate protection.

Nobody said the test is BS.
It is, however, old and outdated, and somewhat flawed in it's original
form. MUCH has changed in lubrication science in the intervening 10
years, and as pointed out, Taxi service is hardly representative of
most daily driving. You are free to believe whatever you care to
believe, and the last poster's suggestion that you buy a couple cases
of Pennzoil and attempt to get 200,000 miles (or even Km) out of your
engine on it is good advice if you truly believe the published test.

As for evidence, how's 37 years' experience? From a professional auto
mechanic?