[AZTEC MUZZY]

Hey there just looking to see if any one would recomend what weight engine oil to use with my 289 (no mods) some one told me 10w 40 semi synthetic
any help would be great

[Jonk67]

A 10W40 would be a fine all around wt., didn't say where you live or what climate, that may make a difference depending on extreme heat/cold. What's more important is to make sure there is enough ZDDP in the oil you use. They have recently lowered the ZDDP (ZincDDPhosphorous) in most oils and this is needed in our older hyd. flat tappet engines for lubrication of the cam primarily. From what I've researched you want between 1000 and 1200 ZDDP preferably.
Some Mobil 1 full synthetic have 1000 ppm ZDDP, or you can use an additive - Zddp+, compcams additive, GM EOS, etc. at every oil change with whatever oil you use.
Jon

[AZTEC MUZZY]

Thanks yer its pritty fine weather all year round here no extremes, so it is ok to run a full synthetic oil then as long as it has resonable zinc leavles?

[Jonk67]

Yes synthetic is fine with proper ZDDP levels.
Jon

[Potro65]

I just did a complete job to my original 289, 1965 engine.

Flat tappet technology calls also for "old" oil technology as far as oil content or ingredients.

My engine builder (and CompCams) say to use MONOGRADE 30 W oil with ZDDP additive. I am using Shell, Rotella T, 30 W + additive.

Basicaly speaking, that is what those engines used and were engineered for back on those days. Zinc and phosphorus were almost eliminated for new enginges because of environmental reasons.

For what I know the use of modern multigrade oil on "old" technology engines is not adequate. Critical internals will wear more rapidly. If you try to get this old engines to the extreme (even if they are just rebuilt) you wil have a blown engine in just a couple of thousands miles, or less.

So, I will go: old technology engine = old technology oil.

Hope this helps.

Potro65