The e-mail below was posted to the North Carolina MG Car Club list by
Max Fulton, of the Flying Circus English Cars in Durham, NC. To me, it
seemed to have some new information on the subject related to the
level of ZDDP to detergents in the oil. Max gave me permission to post
it to 6-Pack and the Triumph list. I am posting in 2 parts due to size
limitations.
NFI in Flying Circus. :-)
Thanks,
Larry Griffin
71 TR6
Max Fulton to ncmgcc
Hey All:
I attended the BMTA (British Motor Trade Association) conference this
weekend. There was an excellent presentation, done by Lake Speed Jr of
"Driven", a Joe Gibbs Racing subsidiary. He is a Tribologist-- "the
study and application of the principles of friction, lubrication and
wear."
He explained the concerns with oil and flat tappet camshafts (which
they use in NASCAR as well.) From what I've learned elsewhere, his
elaboration of the facts and data made a lot of sense and I found
nothing to disagree with.
For your edification, I'd like to share the highlights.
a) It's the phosphorous in the Oil (NOT the Zinc) that forms the
barrier to abrasion on the surface of the lifters and camshaft.
However, the phosphorous is carried in ZDDP-- Zinc
dialkyldithiophosphate--and thus why it's sometimes just abbreviated
as "zinc".
b) the amount of detergent in the oil prevents the further deposit of
the phosphorous. So, while an oil might claim a certain quantity of
ZDDP (say, 1200 ppm), IF the amount of detergent is greater than this
number, this is a worse oil for our engines than one, say, with a
lesser amount of ZDDP yet an equal amount of detergents. (And more
ZDDP than detergents, esp. with some hi anti-friction additives, is
best). Non-detergent oil, esp. for Break-In, is required. (This lays
down the all important first layer of phosphorous, a polar molecule
which requires heat to activate.) Racing oils have high ZDDP, high
anti-wear additives, and low detergents. (The oil is NOT expected to
be in the car very long!)
b-2) Corollary: Any HIGH-MILEAGE oils will have high detergents! Just
like there is no need for high-mileage tires in your old classic car,
a high-mileage oil is the exact opposite of what you want!
c) Boron and Molybdenum are the anti-friction additives. Moly, though,
is the best and most expensive, but is also magnetic (boron is not)
Therefore, using a magnetic pickup (drain plug or magnet on oil
filter?) to trap metal particles is only rendering your oil less
effective!
d) The FINISH on your cam and lifters is also very important! The
rougher the finish, the deeper the phosphorous film required, and thus
the more phosphorous needed in the oil.
**** This explains the raging debate on this issue: One guy claimed to
have wiped out a camshaft in only 900 miles using oil <x>, and another
guy claimed that oil was fine, the first guy must have done something
wrong, blah blahb& and it turned into a pissing contest. IF one allows
for the first cam to have a rougher finish, then the oil would not
have sufficed for that camshaft but may have been passable for the
other guys, etc. ****
e) Zinc Additives. (This is what we've been doing at FC). These are
actually hit and miss. Depending on the detergents in the oil used,
you STILL might not be adding enough zinc to make a difference. (Mr.
Speed showed one unnamed oil that was 3 times the amount of
detergents, and in a 20w-50 blend no less!) Also, the
detergents/dispersants might view the "external" zinc as a foreign
object and actually work to remove it! It is best, then, to use an oil
that was blended with the appropriate amount of ZDDP to begin with!
f) Diesel oils have a high level of ZDDP, but often more of detergents
(as it's a filthier combustion process). Recently Rotella changed it's
formulation, so it's now suspectb&
________________________________________
6pack@autox.team.net
Archive: http://www.team.net/archive
Unsubscribe: http://autox.team.net/mailman/options/6pack/mharc@autox.team.net
|