New to the Group

[tbucketnut]

I use the NAPA 90 weight mineral oil in the sm420 and recommend it for the ones I rebuild for people, I found the newer more slippery 90 weights can make for bad shifts with the 3rd and clutch gear synchros in my opinion. Runs about 15 bucks a gallon takes between 6-6.5 pints.
I dont think you can go wrong with any hypoid gear lube for GL-2 through 5 for the diff. If you have a clutch type limited slip or posi you will need friction modifier.

Steve

[LEWISMATKIN]

Use a high quality 85w140 gl-4 gear oil. Personally, i use sae140 gl-4 gear oil, but i know that can be difficult to find.

[LEWISMATKIN]

Originally Posted by tbucketnut

I use the NAPA 90 weight mineral oil in the sm420 and recommend it for the ones I rebuild for people, I found the newer more slippery 90 weights can make for bad shifts with the 3rd and clutch gear synchros in my opinion. Runs about 15 bucks a gallon takes between 6-6.5 pints.
I dont think you can go wrong with any hypoid gear lube for GL-2 through 5 for the diff. If you have a clutch type limited slip or posi you will need friction modifier.

Steve

The only problem with using mineral oil in any gear box is the fact that mineral oil won't mix with EP rated lubricant-if any EP lube is introduced into the lube, it will cause a chemical reaction causing the mineral oil to coagulate like blood clotting and causing all the bearings, syncronizers, and bushings to fail. If you use it, make sure that is all that goes in whatever you put it in.

[tbucketnut]

Good point Lewis, The 64 will get an R&R in the next couple months, its gear oil looked to be original when I changed it out last month. It was the nastiest I have seen too.

Some of the latest and greatest synthetics lubes I have found are so slick the synchros (especially worn used components) have a hard time meshing the gear as smoothly.

I believe mineral oil was oem until mp gear lube came along it was gl-1. When that happened must of been into the 60s some time.
I believe some sm420s found there way into many new vehicles after that into the 80s maybe abroad.

Thanks for your point.

[jmfurgason]

Sooooo is Shell Rotella T4 the best oil to use in a 305E gas motor???

[LEWISMATKIN]

Originally Posted by jmfurgason

Sooooo is Shell Rotella T4 the best oil to use in a 305E gas motor???

it depends on your climate. If you are in a climate that averages 32 degrees F, or below 6 months of the year, yes if you use 15w40 T4.

[jmfurgason]

Not that cold in southern New Mexico, 3 months at night are cold . Just looking for the best oil for 305E V6. Thanks for input, any other suggestions?? JM

[LEWISMATKIN]

Originally Posted by jmfurgason

Not that cold in southern New Mexico, 3 months at night are cold . Just looking for the best oil for 305E V6. Thanks for input, any other suggestions?? JM

I would use the Shell T1 SAE-40 or something with similar ratings.

[jmfurgason]

Thanks Lewis ,will check out Shell T1 40W, Have a great Sunday. JM

[Ed Snyder]

Originally Posted by jmfurgason

Not that cold in southern New Mexico, 3 months at night are cold . Just looking for the best oil for 305E V6. Thanks for input, any other suggestions?? JM

I'm sure we all have our own favorite oil for our V6 engines, JM. This topic seems to come up every couple of years. My favorite is Amsoil which I've been using in all my vehicles successfully since 1974. Amsoil has developed dozens of different engine oils since then, and many other lubricant products as well. My favorite for our old V6 engines is a high zinc oil available as a 10W30 or a 20W50. See https://www.amsoil.com/shop/by-produ...?code=ZRTQT-EA.