<VV> Zinc and Oil

Eric S. Eberhard flash at vicsmba.com
Thu Oct 8 18:11:59 EDT 2009

Opinions on oil vary so much, and the more you read the more confused 
you get.  Here is a good technical article on the problem with cams 
and flat tappets and 
zinc:  http://www.compcams.com/Base/pdf/FlatTappetCamTechBulletin.pdf

These are my opinions:

I would make sure my oil was designed for flat tappet engines.  For 
break in and everyday use.  Many companies (go to their Web Site) 
have at least one oil for "racing/flat tappet engines"  Some people 
believe in additives, some say they don't mix well and hence do not 
work.  And too much zinc is worse than not enough.  So I prefer to 
buy mine ready to go.  These come in synthetic and dinosaur.

I use Mobil 1 15-50 in almost everything -- diesel tractors, 1957 2 
cyl John Deere gas tractors, Powerstroke diesel, Land Cruiser 3B 
diesel, and a bunch of others.  I have had great luck, but this is 
only anecdotal.  We live in central AZ which has "odd" 
weather.  First of all, 50 degree swings between night and day are 
the norm.  Second, the summer highs are 105 and the winter lows 
14.  In other words, extremes.

We have a 1980 4x4 Toyota we bought new.  245K miles, finally I see a 
small puff of smoke when I start it, never have to add oil between 
changes.  It has always (except the 1st) had Mobil 1 although 15-50 
came out later.

We have a 1992 Ford 460 big block and 1999 Powerstroke Ford diesel 
with well over 120k -- no work ever, no loss of oil, no smoke in the 
gasser (the diesel, depending on how I set my chip, can burn 
black!  but it is not oil).   Both, except for the dealer's oil, only 
had 15-50 Mobil 1.

I rebuilt two Corvair engines, one at a Corvair specialty shop that 
breaks in the engine the "traditional way" using 30 weight Castrol or 
whatever.  The other was a mechanic that does a lot of Corvairs.  He 
also did things the traditional way.  Both engines got flat cams in 
under 20k miles.  I rebuilt two others -- one myself and one by a 
shop that does a lot of old cars.  Both have only had Mobil 1 15-50 
in them -- 20k, no cam problems (or other problems).  I broke them in 
with initial firing, and break in, and normal use, all with the same 
oil.  Mobil 1 15-50 is listed as "for racing/flat tappet engines" -- 
it has a large amount of zinc and related, just like the oils of 
yore.  They have 3-4 other oils with fairly high zinc, but not as 
high.  Mobil says their synthetic is fine to break in an engine, 
Amsoil says no ... so check that as well as the zinc and preferably 
specific reference to flat-tappet engines.

Again -- this is proof of nothing except that I have had very good 
luck with this oil.  I read the link post earlier here about oils and 
that author is not hot on 15-50.  Having said that, he was careful to 
mention that oil should be chosen based on the operating temps ... 
and few people have the extremes I have here in AZ.

If I were you I would break it in with Mobil 1 15-50 and run it on 
that forever.  Or find another oil you like that is specifically 
recommended by the oil company for flat tappet engines.  Skip the 
additives (I have a few bottles if anyone wants to buy them :-) ).  I 
prefer synthetic because generally you can go longer between changes 
which saves time, money (less oil to buy, fewer filters to buy) -- 
Mobil 1 recommends 15k miles between changes (I change at 5k no 
matter what).  It does not leak on Corvairs any more than any other 
oil.  In fact I have 3 Corvairs now that do not leak a drop (of 
engine oil, the PG is another matter).  I would also make sure the 
builder really prepares the cam correctly (grease, etc, lots of 
little rules and tricks on this).

Good luck,


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