Oil selection.

I have included here a question from the Mobil Oil website and their answer, followed by my comments.  Since originally posting this some of the oil specifications have changed.  As of 2018 you can find the current specs for Mobil 1 oils at: https://mobiloil.com/~/media/amer/us/pvl/files/pdfs/mobil-1-oil-product-specs-guide.pdf

Question:

Does Mobil 1 Contain the Additive for Flat Tappet Cams?

I build a few engines a year as I do muscle car repairs and I have been having a lot of camshaft failures.  I just read that it is because the oil no longer has the additive for flat tappet cams. Can I use Mobil 1 to break in fresh rebuilt engines of '60s and '70s tech? Is it too slippery for new ring break-in? Will it give protection on new cam and lifters?

-- Frederick Neidlinger, Dover/Dover AFB, DE

Answer:

For older, flat tappet engines where wear may be more of a concern, we offer a number of oil products which are higher in phosphorus than API SM/ILSAC GF-4 oils.  These include Mobil 1 15W-50 (1,200 ppm), Mobil 1 0W-40 (1,000 ppm) and Mobil 1 High Mileage 5W-30, 10W-30 and 10W-40 (900 ppm).  For all newer engines and flat tappet engines in normal service, API SM/ISLAC GF-4 oils are preferred for better fuel economy and for the protection of catalytic systems with lower phosphorous (800 ppm).  See details on our chart - http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf

Vintage Performance Comments:

In general newer oils labled SM ( Mobil 1 15W-50 is an exception ) and SN, in order to meet those standards have smaller amounts of the zinc and phosphorus additives than were in SL and older rated oils designed for older flat tappet/lifter engines. We strongly recommend using oils that have the older/higher levels of these components in all of our engines. Review the Mobil Oil chart above for current levels of additives in their oils. Other oil companies should have similar information available on their oils.  Make sure that you are looking at the most up to date information as levels of additives in specific oil products are subject to change. 

The oil that we used in street engines was Mobil 1 High Mileage 10W-30, SL rated, ( also available in 5W-30 for very cold weather use ).  This oil is usually available in auto parts stores and is often on sale, but as of 2018 the SL rated version with higher zince an phosphorous may no longer be available.  We use synthetic oil as it provides better lubrication at both high and low temperaures, and for street cars such as the Volvo 1800S that used an oil cooler, it eliminates the need for the cooler. 

For break-in, even higher levels may be beneficial and we use break-in additives, such as Lucas break-in additive. We also use a petroleum based oil for break-in, on the theory that the rings will seat better and faster with an oil that is less "slippery" than the synthetic oils.  We change the oil once or twice during the first couple hundred miles, and this can get expensive with synthetic oils. For many years we have used Mobil 1 15W-50 in our race engines. These engines have been designed for use with multi-grade oils. We do not recommend the use of straight 50 weight race oils.