Engine What oil do you use ?

[PRM]

What's the recommended oil for a 1986 AMC 258 i6 / 4.2l I6 here in the mid-Atlantic area?

Is synthetic the way to go?

 

[caveman]

I've been running a straight 30 W for years with no problems. I also add some ZDDP additive.

 

[Manic Mechanic]

in my 85 ive run royal purple 10w40 since rebuild. on used motors not rebuilt yet i run rotella diesel oil 15w40 b/c it still has zddp in it

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[PRM]

Thanks for the replies. I think I'll look for some rotella 15w40. I'm thinking straight 30 in sub freezing might be pushing it a bit

Also, how many quarts?

 

[PRM]

Is Rotella T-4 correct? It specifically mentions acid resistance, whereas T-5 & T6 don't. It's also the only non synthetic of the three.
Also, do you use a regular oil filter, or is a different filter required with diesel oil?

 

[Manic Mechanic]

I'll double check pretty sure its T-4 but ill check. 6 quarts same as all the inline 6s and reg oil filter of ur choice. me i use whatever is on sale. except i never use fram they are trash.

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[Scout1067]

I run Valvoline 5w30 high mileage in mine year round with the Lucasoil ZDDP additive on top of that in my AMC 258 i6 / 4.2l .

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[hole]

15w40
Around me Delo and Valvoline trade off on who has it on sale from week to week. Heck, just picked up 3 gallons for $26 at Costco a couple weeks ago. Wix or Napa brand filters (Wix makes Napa's )

 

[007]

Oooooooo I love these religious discussions! Brands are more religious than weights and zinc. I run 15w40 Lucas Magnum with 20% Lucas Oil Stabilizer. High detergents and high zinc for these flat tappet engines that are sometimes dirty runners. Stabilizer will quiet down those often-noisy AMC 258 i6 / 4.2l top ends. They run a tad cooler with it as well.

 

[caveman]

I only run my rig in the summer. Currently tucked in the shed so the straight 30W is good enough for me.

 

[Lumpy Grits]

Castrol 20W-50, WIX filter.

 

[Manic Mechanic]

i know ur new here and all but look what you started.....

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[Belizean]

Castrol 10-30 since new. 238,000 miles with no problems

 

[cleg]

I did a lot of research on motor oil before settling on one.
It turns out that almost all motor oil available via retail has intentionally low levels of the additives that would be in there to protect flat tappet cams.
The good news about the AMC 258 i6 / 4.2l is that it is not trying to be a racing engine.
The force required to open the valves is not huge.

I contacted the tech data folks at some of the oil manufacturers and the best I could get was some charts on chemical composition.
It seems that they are not allowed to market high ZDDP oils for highway use.

The only retail-available motor oil I could find with documented percentages of ZDDP that were like what was offered in the 1970s when these motors were built is Rotella T1 SAE-30.
It's sold as motor oil for tractors/heavy equipment, maybe to avoid the "highway use" problem.
Not all Rotella oils use the same chemistry.

I wrote all of this down at the time so I'll look for the numbers and post them when I have time.

Bought my 84 CJ7 with AMC 258 i6 / 4.2l inline six and some bad valve tapping realizing I was probably looking at some major work.
One cam lobe was worn off and I replaced the camshaft & bearings.

Running the Rotella T1 SAE-30 since the rebuild.
So far so good.

Cleg

 

[j6824]

Another vote for Rotella

 

[Manic Mechanic]

its all emissions . mostly steaming from comyfornia. i even read that the new camaro ss, 1LE etc cant be sold there after jan 1 2021

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[cleg]

I am not a chemist so please take this for what it's worth.
It is the best answer I could come up with from the available info.

I located the note I had concerning the ZDDP level in Rotella T1 SAE-30.
It was identified as a percentage that can be converted to ppm.
Also in the attached MSDS sheet on page 2 1.0 to 2.4% zinc dialkyl dithiophosphate (ZDDP).

It seems that the manufacturers do not (are not allowed to?) advertise the ZDDP level to prevent people like me from using it in old passenger vehicles.

Rotella T1 SAE 30 non-synthetic.
1.333% ZDDP = 1,386 ppm zinc and 1,240 ppm phosphorous.
Suitable for flat tappet cams.

 

[007]

It seems that the manufacturers do not (are not allowed to?) advertise the ZDDP level to prevent people like me from using it in old passenger vehicles.

I think a lot of them just assume no one cares and those that do will ask. A vast majority of newer oils are of course made for newer engines that have tighter specs and tighter requirements and specifically don’t need the zinc like older engines do.

Like I stated earlier, the religious part of this is mostly based on brand and loosely based on experience regardless if it was fair or not. I won’t tell anyone why I won’t use Shell or Quaker State because I even know it’s stupid.

Likewise I’ve seen first hand several scenarios where an oil was replaced with Lucas and the results were beyond impressive. One was in a fleet of semi’s (80+) and the other was in diesel tractor pulling. The results in semis were confirmed by lab testing and the pulling tractors by the life of main and rod bearings.

Their use of a pre-screen before the filter makes it super easy to inspect fragments that obviously indicate wear, but can also indicate what part based on the type of fragment. Brassy fragments indicate severe bearing wear.





Now, back to religion, I guarantee there’s someone on this board they would never use Lucas because of some experience or stupid reason. That’s fine. I get it. Doesn’t make either of us right or wrong.

That said, here’s the TDS for what I use for what it’s worth.




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[Belizean]

This is what the machine shop that did my machine work said to use. Has the zinc that is needed .

 

[007]

This is what the machine shop that did my machine work said to use. Has the zinc that is needed .

It does. Have a buddy running it in a race car...mid 90’s small block Ford.


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