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Discussion Starter · #1 ·
This is from LN Engineering:

For current Mobil 1 users, Mobil 1 15w50 EP now is an SM formulation, with only 0.09% to 0.10% Zn and P when it's previous SL formulation had excellent levels of both Zn and P! This is even less than what is found in Mobil 1 0w40. I recommend using EOS at every oil change to increase these levels to at least 0.12%. It is worth noting that Mobil 1 V-Twin 20w50 retains an SG classification with unchanged Zn and P levels over 0.14% Zn and P, but for most users, a 20w50 for year round use is unacceptable for cold-startup protection, but as much as twice the price of the normal Mobil 1 oils. Mobil 1 also makes a 10w40 MX4T oil with the same anti-wear additive levels, but I am afraid for cars with catalytic converters, this oil will shorten their life - a small price to pay for additional engine protection.The new SM formulation of Mobil 1 15w50 seems to have in addition to reducing the Zn and P significantly, they also reduced the boron from 226ppm to 72ppm and eliminated all trace of sodium and magnesium, two other known anti-wear additives. It would look like it's an entirely new formulation than the SL it's replacing. I strongly recommend those running Mobil 1 15w50 switch to Mobil 1 V-Twin 20w50, which still is an API SG oil, which has the highest level of zinc found in any motor oil, which adding the boron at levels typically only seen in low Zn and P formulations. This should technically provide the best protection in my opinion. We will be testing their 10w40 4T Racing Motorcycle Mobil 1 formulation to see if it is similar.

Here's a link to their whole article on oil…….it's good reading.

· Premium Member
2,256 Posts
I've been using M1 for a long time. I used it exclusively in my old 422 without issue. In my 427, I haven't had very good luck. Can't say for sure it's the oil's fault, but I decided to switch. I encountered an unusual pushrod/rocker cup wear problem over the winter. To fix this I switched oils and bumped spring pressure and went to a bigger pushrod. Not sure what the culprit was, but going to a "race" oil is part of the planned solution.

I was using the M-1 5-30w that can be bought at WallyWorld for $22/5qts.
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