Motor Oil Fact or Fiction - Engine Builder Magazine

Motor Oil Fact or Fiction

1. Synthetic motor oil is too slippery. It causes roller bearings to
slide instead of roll, and that causes the bearings to fail.

Fact or Fiction? – Fiction

If you have ever flown on a jet airplane, you have enough experience to
debunk this myth. All jet turbine engines utilize rolling-element
bearings, and every jet turbine engine runs on synthetic oil. In fact,
only synthetic oil can handle the high speeds and extreme temperatures
found in turbine engines. This myth is very popular among the motorcycle
crowd, and the roots of this myth are based in the misapplication of
passenger car motor oil. The power density of motorcycle engines place
greater shear forces on the motor oil than passenger car engines do. As a
result, most passenger car motor oils are not appropriate for use in a
motorcycle engine. This is especially true of passenger car motor oils
optimized for passenger-car fuel economy. These oils are the least shear
stable, and should not be used in motorcycle engines.

Failures in motorcycle engines have long been blamed on synthetic oil.
However, the problem was is not the synthetic base oil, it’s the fact
the synthetic oil is not formulated for a motorcycle engine. A
properly-formulated synthetic motorcycle oil will provide superior
performance in a motorcycle engine. Likewise, a properly-formulated
synthetic passenger car motor oil will provide superior performance in a
passenger car engine as well.

2. Flat tappet engines can’t use synthetic oil because the lifters won’t rotate – the synthetic oil is too slippery.

Fact or Fiction? – Fiction

This is a variation on the first myth that has become popular since flat
tappet camshaft failures began to increase about 10 years ago. Like the
first myth, the origin of this one also relates to misapplication of
passenger car motor oil. About two decades ago it was common for racers
to use off-the-shelf motor oils in their racing engines. At that time,
these motor oils contained enough ZDDP (aka Zinc) to protect the
aggressive camshaft designs found in racing engines. Because NASCAR
teams raced for hundreds of miles each weekend at very high oil
temperatures, it was common practice to use synthetic motor oils.

You could purchase premium synthetic motor oil right off the shelf back
in the early 1990s that was capable protecting a flat tappet race
camshaft. By the time 2005 rolled around, however, the ZDDP levels in
off-the-shelf motor oils had been reduced due to EPA regulations for
passenger cars, and this reduction in ZDDP found these formulations to
be deficient for protecting flat tappet camshafts. As a result, the
racers using off-shelf-motor oils began having camshaft failures, and
because many racers used synthetic passenger car motor oils, it appeared
the cause was synthetics.

Today, every NASCAR team still runs engines that use flat tappet cams,
and every one of those flat tappet engines are lubricated with synthetic
motor oils. However, these synthetic motor oils are special
formulations with more ZDDP to protect the flat tappet camshaft. Again,
misapplication is often the cause for problems that appear to be oil

3. Once you use synthetic motor oil, you can never change back to conventional oil.

Fact or Fiction? Fiction

An engine running conventional motor oil can change to synthetic motor
oil, and you can change back to conventional if you would like. The
likely start to this myth stems from an actual good practice – it is not
a good idea to switch back and forth between different brands of oil.
You’ve probably heard an old-school mechanic tell you to pick a brand
and stick with it. That is a pretty good idea. However, it is more
important to use the correct type of motor oil for your engine.

Most high performance and racing engines are actually initially broken
in on conventional motor oil (specially formulated for engine break-in)
and then switched to properly-formulated synthetic motor oil for use
after the break-in process. Again, the key lesson here is to select an
oil formulated for the specific needs of your application and then stick
with that product.

4. Synthetic oils are bad for engines with old seals.

Fact or Fiction? Fact

You thought all of these would be fiction didn’t you? Well, this one
turns out to be true in most applications. Notice we said most
applications. While some exceptions to this rule can be found, the
majority of times this rule does apply – don’t use synthetic motor oils
in old engines with original seals.

When we say old engines, we mean engines that were built before 1992.
Synthetic base oils are not compatible with many of the traditional seal
materials, and even with "seal conditioner" additives, synthetic oils
are harder on traditional seal materials than conventional oils. To
avoid leaking seals, avoid very light synthetic motor oils in older
engines. The low viscosity and resulting free flowing nature of the
synthetic makes it easier for the oil to find a leak path.
Higher-viscosity oils tend to leak less. Thus, most old-school hot
rodders use thicker-viscosity conventional oils like a 15W-50 or 20W-50
in their engines.

Modern engines and modern seal materials are designed to be compatible
with synthetic motor oils. This is so you can use a synthetic in a
freshly rebuilt Small Block Chevy for your 1969 Camaro. If you have a
‘69 Camaro with the original seals though, then you should use a
conventional oil. Now if you also happen to have a 2013 Camaro, you
should use a synthetic motor oil in that engine.

Hopefully all of this puts to bed any worries or fears related to any
myths you’ve heard about oil. More importantly, we hope you now see the
importance of selecting the proper type of oil for the needs of a
specific application. Just like a tailored suit fits the person it was
tailored to better than an off-the-rack suit, application-specific
formulas provide a better fit for the unique needs of performance
enthusiasts than off-the-shelf motor oils.

Source: Driven Racing Oil

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