i have been looking into this a bit since i have a new engine that will hopefully get installed sometime soon ... i have read a bunch of technical articles that i got from a porsche specialist / master mechanic friend who now focuses on vintage and race cars these days ... but also keeps up with some very high end P cars for a mutual friend of ours. we had a chat about break in procedures and everything said below is on target with his thoughts, with one exception ... use a break-in oil and only keep it in for 500 miles, changing oil and filter. the break-in oil should be a high detergent oil to collect and get all of the crap out of the engine (assembly oil, etc.). a couple of mineral break-in oils i know of are Brad Penn break in oil (sae 30) and Motul break in oil (10w-40). you can also use the same oil that you are going to run in the engine.
we then got into a lengthy discussion about engine oils in vintage cars. i expected to hear the typical - 'stay away from synthetic oil' in this age of cars. we talked about a few conventional (mineral) oils - his favorite was a high ZDDP oil - Motul classic performance 20w50. he thinks that valvoline vr1 and kendall are very well priced and easily sourced, and also have good ZDDP content, but what he doesn't like about conventional oils is the propensity to become acetic which is problematic ... they also have a condensation problem and the oil not getting hot enough to boil it out.
here are a few things you should watch - perhaps overly simplified
this talks about some oil basics and what happens to conventional oil as it ages - additives breaking down, becoming thicker at cold temperatures and thinner at high temperatures (neither are good)
the second -
synthetic vs conventional oil - a little interesting content
his recommendation is to use a partial synthetic at a minimum ... Brad Penn 20w-50 or Motul 2100 15w-50. the downside is that Motul no longer has the 2100 on their website ... it was a partial synthetic (similar to the 4100), but was made for engines made after 1970. he is going to have a discussion with Motul on the former 2100 vs the current 4100 partial synthetic oil.
he also feels that a full synthetic would be the best choice, especially an ester based synthetic like Motul 300v 15w-50 (its just ungodly expensive - about 15 bucks / liter). the important aspect is to use similar viscosity oil and not the majority of the synthetics available with 0w-20 to 0w-40 ... or possibly 5w-40.
that being said, i know full synthetic is really good as my 911s has been running mobil 1 0w-40 its entire life and with 80k miles it still reaches all of its original specs. but i can't get over having heard to stay away from full synthetic in vintage cars - even with a new engine. so, unless somebody convinces me otherwise, i am probably going to run Brad Penn 20w-50 (partial synthetic) in my new engine.
