Tested the way they are actually used — mixed at the recommended ratio and
put through engine heat — none of these five additives improved on straight
Pennzoil Ultra Platinum overall. Liqui Moly came closest, tying the control
oil in the overall ranking and posting the lowest evaporation loss of
anything tested at 2.83 g. Bestline is the one genuine standout in a single
category: a 4.70 mm wear scar against the control oil's 5.37 mm, the only
blend to beat straight oil on wear protection after heat.
The neat-fluid results are the trap. Straight from the bottle, Archoil
(1.08 mm), Bestline (1.62 mm), and ProLube (2.08 mm) produce spectacular
wear scars against motor oil's 5.37 — and that is exactly the demonstration
additive sellers perform. Mix them properly and heat them, and Archoil rises
to 5.54 and ProLube to 5.84, both worse than the oil alone. ProLube fared
worst overall: heat exposure pushed its cold flow from 69 seconds to 128, and
the lab found it lowered the oil's total base number the most, from 7.4 to
5.8, consistent with an acidic component consuming the oil's reserve
alkalinity.
The lab analysis explains most of the results. Substituting any additive for
part of the crankcase oil dilutes what the oil already contains: every
product reduced total zinc, and all but Archoil reduced detergents,
dispersants, and TBN. Archoil was the exception because it brings its own
chemistry — high potassium and boron from its potassium-borate friction
technology, and a TBN of 12.2 against the oil's 7.4. Liqui Moly and Bestline
raised MoS2 content, and ProLube was the only one to add phosphorus. Lucas
turned out to be mostly a viscosity enhancer with little anti-wear additive,
which matches its flow results exactly.
The real-world driving results are the weakest evidence of the lot, and they
point the same way. Each additive ran in a different vehicle against that
vehicle's own back-to-back baseline, so they are three separate comparisons
rather than a ranking: ProLube gained 1.48 MPG in a 2020 Chevrolet and took
0.15 second off its 0-60, Liqui Moly lost 0.50 MPG in a 320,000-mile Suburban
driven in light rain, and Bestline cost a 4Runner 2.21 MPG. The two
acceleration changes that were not ProLube's — 0.05 second gained and 0.02
second lost — are inside the noise of any road test. Nothing here supports
the power or economy claims on the bottles.
The practical conclusion is narrow: in a healthy engine, a quality oil
changed at sensible intervals beat every additive here. Additives make sense
as a targeted fix for a specific mechanical problem, not as insurance on an
engine that does not have one.