Rhodrich, first of all, thanks very much for taking the time to share your experience and help the community, that's what makes our hobby great
I am here also sharing my experience i aquired over the couple decades involved with these engines. Not only the stock ones, but specially with the high revving and stroker engines. On these we need to modify the oil system to have an adequate supply in order to make the thing stay together :msn4:
The engines people build on the Samba are mostly highly modifed, the-most-bhp-i-can-squeeze type, so if they use a thinner oil it will make more power, but tolerances have to be tighter in order to have a decent oil film and therefore protection. It's all in the building and blueprinting process, so without knowing how tight or loose an engine is, it's hard to give a proper oil recommendation.
So what i am posting here is what works for me, and for those who know me, they know i do not settle for nothing less but the best and all the engines i build i treat like my children :mrgreen: :mrgreen:
This has been taken from the 1979 owner's manual, the year with the last improvements for the ACVW engine. As you can see, the SAE 30 is recommended up to about 25 deg C. Note the 20w50 though; it has a wide range of suitability which well fit our current climate. Vw never recommended SAE 50 and i never did that too.
An SAE 50 is not the same as a 20w50, and also an SAE 40 is not the same as a 15w40. The straight oil will be thicker at higher temps then the Multiviscosity, so they cannot be compared.
Also i never use straight 50 as they are really thick and also indequate due to not having modern additives, etc.
You said that a thicker oil has increased pressure, that's true. What is not true is that it bypasses the oil cooler and the cooler does not see any flow of oil. Even with a 30mm pump and thick oil like an SAE50 on a stock unmodified engine it will always have some flow of oil, but not all of it, therefore under these circunstances, the engine can run hotter.
On the engines i build, i recommend the 20w50 mineral with the correct amount of ZDDP. I invalidate the warranty if the customer does not use it. By the way, i offer 24 months on a certain range i have and even 12 months on performance engines which normally nobody warrants them.
On this forum, there is quite a few people that have i built engines for, mostly 1776's, 1 1600 and 1 1955 cc's. All of them do not have any external cooler, only the full flow filter as i fit to all my engines regardless of what they are. The 1955 for Brad is on the verge of getting an external cooler for not being possible the install of a deep sump, but i told Brad it was likely the case when we decided to go from the initial 1776 to a stroker 1955.
There is a customer of mine on the Late Bay forum that has one of my 1955's exactly the same as Brad's but with the deep sump, he uses the Bus for work and camping the whole year and has no need for the external cooler.
One thing though; i insist in using only Gen VW complete set of tinware, that makes the cooling system properly adequate. And off course there is the building process and the tuning, which the latter is also ultra important.
As time went on, the oils have evolved and we got some of that evolution while the ACVW was still being produced, so for that reason VW decided to suggest the use of the Multyviscous oil. And i did that too. Only mineral oil here that is, if the question arises
Abel
