Best oil for My Slant 6

[timk225]

I used Castrol GTX 10w-30 or 10w-40 in my Slants for many years. Conventional oil, not synthetic or a blend. Never had an oil problem.

 

[Mopar Pearl]

I used Castrol GTX 10w-30 or 10w-40 in my Slants for many years. Conventional oil, not synthetic or a blend. Never had an oil problem.

Thank you

 

[moparstan]

Hey All,
Need suggestions for the best oil for my 1966 Plymouth, Valiant 200. Slant 6.
I had all the specs written down in a note book but some how I have lost it.
Any help would be appreciated.
Thank you,
Mopar Pearl

I’ve been running Castrol GTX 10w-30 in my ‘73 Dart slant six since 1991. At that time I rebuilt the engine (169k mi) and found a lot of sludge (previously used Havoline). Did a partial rebuild five years ago, zero sludge and minimal wear. Currently at 387k mi. So I’m satisfied. I have some of the Castrol Classic with ZDDP and will be using it soon.

 

[Newbomb Turk]

He likes to add drama. Direct injected engines, you know the ones getting a shot from the cylinder wall is what he's talking about. At low speeds putting around town they need a special oil that has additives that resists oil dilution. I did my research on that stuff when I was buying oil from my ex-GF's 2.0 DI turbo Camaro.

We are talking about a carb'd slant 6 here.

When you argue with a tribologist, who has spent his LIFE learning and building oils is proves you a fool.

I’ve been telling people for DECADES to not use diesel oil in gasoline engines, but guys like you come along with anecdotal evidence like it’s gospel and the sad ignorance continues.

Unless you are doing used oil analysis at every oil change you don’t have a clue what you are getting.

DI or not, diesel oils are NOT for use in gasoline engines.

And WTF? It’s 2025. When will people stop being cheap and start buying oil that is at least 20th century technology?

My wife has a 2017 Durango with a Hemi. When she got it, it was using a quart of oil every 1k. That is damn unacceptable in 2024.

So I ordered a case of very expensive oil and changed it out.

After the first 700 miles it used 1/2 a quart. I topped it off.

Over 8000 miles later the oil level hasn’t moved.

What does that tell you? I know what it tells me.

It says ring seal is far Far better than it was. Oil seals the rings.

So keep using junk because you’ve always done it.

For everyone else, spend some time researching oils, additives and which brands use what base oils and additive packages and why.

FWIW, there is NO straight mineral oil or “semi” synthetic oil I would use. Ever. PERIOD.

Study base oil groups and you’ll figure out why.

 

[chryslercruiser]

I respect and appreciate the knowledge all of you who have probably forgotten more about engines, and more specifically Mopars than I will ever know!!

BUT I direct your attention to the fact that:

Rotella T6 is listed as a "SN" rated oil.. on the back of the bottle
Here is the Rotella advertisement cut and pasted for easy reference:

EDIT: T4 may not be to the same standard, with I have not looked into!

Shell Rotella® T6 Multi-Vehicle Full Synthetic engine oil performs extremely well in diesel and gasoline engines, meeting both API CK-4 and API-SN standards and allowing mixed fleets to consolidate lubricants.

 

[Newbomb Turk]

He likes to add drama. Direct injected engines, you know the ones getting a shot from the cylinder wall is what he's talking about. At low speeds putting around town they need a special oil that has additives that resists oil dilution. I did my research on that stuff when I was buying oil from my ex-GF's 2.0 DI turbo Camaro.

We are talking about a carb'd slant 6 here.

I respect and appreciate the knowledge all of you who have probably forgotten more about engines, and more specifically Mopars than I will ever know!!

BUT I direct your attention to the fact that:

Rotella T6 is listed as a "SN" rated oil.. on the back of the bottle
Here is the Rotella advertisement cut and pasted for easy reference:

EDIT: T4 may not be to the same standard, with I have not looked into!

Shell Rotella® T6 Multi-Vehicle Full Synthetic engine oil performs extremely well in diesel and gasoline engines, meeting both API CK-4 and API-SN standards and allowing mixed fleets to consolidate lubricants.

Go look up the SN specs and see how that works for the engines we are dealing with.

Those are fuel economy oils. For engines that have so little spring pressure they wouldn’t even be a stock 318 spring and cam lobes as gentle as the rolling hills.

Thin rings, small bores…I could go on.

This information is all over the web. Or better yet, call some high end oil manufacturers and talk to them.

 

[Lenni]

Here is the Gospel Truth on Pennsylvania Crude Oil. It has been referred to as being the best oil in the United States. Crude Oils are either paraffinic base or asphaltic base, or a combination. Paraffinic based oil produces the best lubricants for most purposes. Pennsylvania Grade Crude Oil has superior qualities and is free of asphaltic constituents, contains only trace amounts of sulfur and nitrogen, and has excellent characteristics for refining into lubricants. Pennsylvania Grade Crude Oil is thermally stable, has a high viscosity index, is resistance to oxidation and is high in paraffin and other waxes making it highly desirable for refinement into petroleum lubricants such as motor oil. Pennsylvania grade crude oil when seen in reflective sunlight has a green color and under ultraviolet light looks fluorescent. Products refined form this oil are particularly prized as lubricants and many oil companies prominently display the fact that they use Pennsylvania Grade Crude Oil in their products.
Wolf's Head
Pennzoil
Quaker State
(Kendall)

 

[Newbomb Turk]

Here is the Gospel Truth on Pennsylvania Crude Oil. It has been referred to as being the best oil in the United States. Crude Oils are either paraffinic base or asphaltic base, or a combination. Paraffinic based oil produces the best lubricants for most purposes. Pennsylvania Grade Crude Oil has superior qualities and is free of asphaltic constituents, contains only trace amounts of sulfur and nitrogen, and has excellent characteristics for refining into lubricants. Pennsylvania Grade Crude Oil is thermally stable, has a high viscosity index, is resistance to oxidation and is high in paraffin and other waxes making it highly desirable for refinement into petroleum lubricants such as motor oil. Pennsylvania grade crude oil when seen in reflective sunlight has a green color and under ultraviolet light looks fluorescent. Products refined form this oil are particularly prized as lubricants and many oil companies prominently display the fact that they use Pennsylvania Grade Crude Oil in their products.
Wolf's Head
Pennzoil
Quaker State
(Kendall)

Consider the source.

The notion that Pennsylvania crude was all that and then some was debunked in the 1950’s.