Modern oil in old motors

[pls01]

Some recent articles suggest that modern oils won't properly lubricate older engines.  An extreme pressure additive, zinc dithiophosphate (ZDDP), has been removed to protect the catalytic converter on newer cars.  This causes flat tappets to spall and cam wear.  Recommended fix is an oil additve package or diesel rated oil.
   
   I'm thinking of Shell Rotella 30 wt.  Anyone have experience with this issue in a Bristol engine?

[administrator]

There's an article on this topic generally and ZDDP in particular in the current FBHVC newsletter (page 5):
   
   http://www.fbhvc.co.uk/assetts/newsletter-pdfs/FBHVC%20Magazine-Dec-08.pdf

[aex125]

Over the last couple of years (starting in 2007) zinc levels have been cut in most oils and so the Rotella-T no longer has the same ZDDP levels as before. For diesel oils the Standard used to be CI-4 which had around 1300PPM of ZDDP and the new designation is CJ-4 which has <1200PPM. For regular oils the old higher ZDDP formulations were SL rated and the new SM rated oils are again lower. If you can find oils with the CI-4 or SL designation you should be able to use them, if not you may want to look for oils that have higher ZDDP levels. From what I read in the past, older engines do best with 1200-1500PPM so that is the target range to look for. The following web site gives some good comparison info on some different oils that are out there
   
   http://www.lnengineering.com/oil.html
   
   It is geared for Porsche/air cooled drivers, but in the FAQ portion, they show Zinc level comparisons. As stated in the article, if you go to racing oils you can ensure you get hi levels of ZDDP; and from the admin post it looks like there might be a new Castrol formulation to use although I have not personally seen it on the shelf in my neighborhood. On a final note, with the formulations changing all of the time, you may need to confirm the ZDDP content of the oil you are buying to confirm what its content is at that particular time.
   Jay

[pls01]

Thanks the articles and Jay's information confirm what I read.
   
   I checked the Shell web site.  The Rotella T single grade straight 30wt is listed CF-4, CF-2, CF and SJ.  This may be old infomation and it doesn't mention the concentration of ZDDP.
   
   Unfortunately, parts suppliers only carry the latest oils, usually API SM.  The local suppliers stopped stocking racing oil.  Castrol USA doesn't list any vintage oils.  Looks like mail order racing oil or ZDDP additive.
   Peter