Frequently Asked Questions

What oil should I use?

I have included here a question from the Mobil Oil website and their answer, followed by my comments. ( All data in the answer may not be current as of Nov. 2011 and there is an update below.)

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
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 -

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 phosporous additives that 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. 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.

Nov. 1, 2011 Update:

The main issue with current oils is that the zinc and phosphorous compounds needed to lubricate non - roller lifters have been taken out of current oils for emissions purposes as the additives degrade the function of catalytic converters. The last street regular street oils sufficicient levels of these additives were rated SL. The newer SM and SN oils have most of the additiives removed. There are some oils for older engines that still have them, as do racing oils, but the companies change the oils often so you just have to keep checking on those that are available to you. Mobil 1 synthetic for cars with high milieage may still have the additives - hard to tell as some stores are still working through old stock and the newer stock of an oil with the same label may be a new version with lower additives. Mobil 1 15 - 50 does notstill have the higher levels unless it is the racing version of the oil. And some of the website info on the oils is not up to date.
Royal Purple still has synthetic oils with high additive levels. We like synthetics as they will lubricate at both higher and lower temps than petroleum based oils.
I have heard of the Brad Penn oils but have not used them. Looked them up today in answer to a customer's question and it looks like the partial synthetic Penn 1  10 - 30 might be a good choice for an all around street oil.