Tom Webber wrote:

Hello all,  I have a question and would like feed back on the use of
Mobile One engine oil.  Should the engine be broken in using a non
detergent for X number of hours then use Mobile One.  Or can the
synthetic oil be used right off the jump?  All comments are appreciated.
 T.W.

Tom,
I would absolutely begin the engine's life on petroleum after a rebuild.
100% synthetic oils reduce friction so dramatically that engine break-in
lasts a long time.  This applies to products with 5-10% petroleum, like
Mobil 1, as well.

The recommendation most often seen is to run a shortened interval on
petroleum to wash out anything left inside from machining or assembly, then
run a second or third interval until oil use stabilizes (hopefully at zero).
The second half is about ring seating, though.  (This is an area that I'd
like to hear about from a rotary builder - how do we know when the apex
seals are seated?)

Many cars are shipped from the factory filled with synthetics - nearly all
the European models (VW has had a synthetic-filled drive train since at
least 1988), many Japanese cars, drive trains of many big trucks in the US,
Vettes, etc.  The initial fill of synthetic engine oil in these vehicles
comes at a price, though.  Corvettes with initial fills of synthetic oil are
taking upwards of 45,000 miles before rings are seating and the engine is
making good power.  Same with big trucks.  Cummins specifies running 20,000
miles on petroleum before switching to synthetics or blends (the best blends
are only 20% synthetic).  Running a single 10,000-mile interval on petroleum
and switching to a synthetic blend stretches break-in (including lower fuel
economy and elevated oil use) out beyond 80,000 miles.

Break-in, significant oil leaks, and very dirty/neglected engines are not
the places for synthetic oil.  Break-in due to decreased friction and
lowered wear, leaks from recurring costs, and dirty engines due to the
significant cleaning effects of synthetic base oils (clean 'em first).

Make sure the petroleum used for break-in has detergents - at least API spec
SB (the current is SL).  The engine needs the detergents and dispersants to
keep things clean.  The non-detergent SA oils should have been off the shelf
in the late 40s...
Andy

Here is a good article from Mazda Sport Magazine.

Paul Lamar

"Lemings, Bob" wrote:

I have to disagree with the long recommended periods using petroleum oils outlined below.  I use synthetics as previously stated and have NEVER had a lack of power or oil consumption problem a la unseated rings.  I drive vehicles at speeds up to 145 mph (not so much as I used to do), cruise on the interstates at 85 mph, and do not lounge around in the vehicle. (I do observe residential and school zone limits--).  I currently have in the household three vehicles - one four, one six, and one eight cylinder - that are approaching 300,000 miles.  The engines have never been opened on any of these, except for a head gasket replacement on the four cylinder.

Bob Lemings

Well that might be true for piston engines but the rotary oil has a much easier
time of it. One can drive a rotary for months and the oil looks great. Still clear.

BTW that Mazda Sport article mentioned fuel in the oil. The oil runs hot enough 
to vaporize any fuel in the oil. You just cannot extrapolate piston engine
experience to the rotary.

Paul Lamar
 
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