Thread: Is 0W40 more resistant to forming sludge? - Bob Is The Oil Guy

Originally Posted By: Gary Allan Quote: Hi, tig1 - Like you I have never seen sludge or excessive varnish formed when using an appropritae M1 product I have. Not that it's a bash on the product. I used it whenever possible from the day it arrived on the market ..well, as soon as I had a new enough vehicle to use it in. My mother's (I think) 1980 or 81 Citation 2.8 did one year oci's with M1 5w-30. Did filter changes at...

Hi, tig1 - Like you I have never seen sludge or excessive varnish formed when using an appropritae M1 product Further than that over the last nearly 50 years I can say that in many direct line comparisons with other similar specification lubricants I have always seen an appropriate Mobil or Delvac keep engines clean - and significantly cleaner than the others! I cannot say the same for some other Oil Co. products but Caltex-Chevron and Shell...

I believe 0W oils have to be made from better base stocks. As for preventing sludge. I wouldn't worry about sludge though. If you are running any high quality oil, especially synthetic or a blend, and you aren't using a known sludger, you should be fine.

Stick with what served you well for the last 225k miles. I also don't think a 40w is recommended for that engine.

Either will work fine. Run out the oci with the 0w40 and then go with which ever is less expensive.

To my knowledge, the M1 HM oils are high in detergents. I remember reading that at some point... I've been happy with the times I've used it (off and on over a few years) Never used 0w40, so no comment on that grade.

I doubt anyone can really answer that except Mobil, who won't. I see your point, the higher spread oils probably have more esther content which in addition to having a high VI also dissolve a lot of stuff. So maybe. It's sound reasoning, but for all we know they pump a bunch of VII's into the 0-40 and they both contain the same portions of grp 3 and 4/5. But to worry about sludge on either M1 is a bit of a stretch, and really EP...

Quote: Hi, tig1 - Like you I have never seen sludge or excessive varnish formed when using an appropritae M1 product I have. Not that it's a bash on the product. I used it whenever possible from the day it arrived on the market ..well, as soon as I had a new enough vehicle to use it in. My mother's (I think) 1980 or 81 Citation 2.8 did one year oci's with M1 5w-30. Did filter changes at recommended intervals with top offs...

In reading about mobil 1 5w40 formula M and mobile 1 0w40 it turns out that the pending poor quality of usa gasoline causes sludge problems with the extended 20 thousand km drain interval which is why MB approved 5w40 for gas engines in the usa, but then withdrew that. Apparently the 0w40 has a better tbn to deal with the [censored] 10%+ ethanol based gas. Interestingly the gasoline approval sheet for MB suggests only 5% max ethanol.

If you purposely left the oil in too long, ran it too hot, and fouled up the PCV system, you could probably get sludge. But in normal use, an engine should not get sludge with any oil. Maybe a little varnish.