Oil Selection F134

Hello,
I'm about to do my first oil change in my F134 engine. It has been rebuild at some point in the past and has a spin on filter. I had the rocker arm cover off and it looked fairly clean but there was some gunk on the inside of the cover. The previous owner said he ran VR1 oil.
I'm aware that most modern gasoline engine oil might not be the best choice due to the cam. In my 4.0L I6 Wrangler engine I'm running Rotella T6 5w40. My concern about Rotella in this engine is that is supposedly has more detergents in it. This may break up any sludge and clog oil passages. Does this sound like a valid concern? Does anyone have suggestions on what oil to use? I'm running the engine year round in Michigan.
Thanks,
Ken

 

rotella 15w40 or any dino oil don't overthink it

if you are worried about sludge, drop the pan and take a peek

 

Thanks for the reply. I'm replacing the pan gasket this week anyway so that should tell me how things look inside.
What would you think of 5w40? Not sure if 15w40 would be too thick in the cold weather
Overthinking things is my specialty

 

Brad Penn 40 wt. Supposed to be good for old flat tappet motors and hot rods. Also comes 30 wt.

 

These old engines have looser tolerances as compared to modern engines. Straight 30W in winter, 20W-40 or straight 40 for summer.
In winter, start the engine and let it warm up a bit before driving.
-Donny

 

Curious...Why not a 10-30 in winter?

I use a straight 30w in summer, but that is because it is a Non-Detergent.

 

Why do you run non detergent oil in an engine that has an oil filter?

 

I always heard never switch an antique engine to detergent. Never once (until now) heard any mention of the filter one way or the other. True though that most of my antiques do not have filters.

I could imagine however that disturbed crud might wind up somewhere bad, even with a filter. Why is it advised never to flush a high mile automatic transmission, even though they are filtered?

 

The odds that whoever had your jeep before running non detergent is slim. Non detergent oil lets crap settle, detergent oil keeps it in suspension for the filter to catch. Most stores haven't carried non detergent oil in quantity for 45 years. I haven't been able to buy it off the shelf around here for more than 30 years. I can get it locally but its not in most auto parts store, I would have to go to a tractor supplier. Since these engines came with an oil filter they probably weren't recommended to run non detergent oil from the factory.

The auto trans is usually ok depending on how hard the trans was used. The thinking is dirty oil provided part of the friction for the clutches and removing it makes the clutches slip from excess wear. I have done it several times in my life with no problem, getting ready to do it on my 2012 Challenger.

 

Thanks for the replies. The '77 Jeep manual calls for detergent oil and I know my engine was rebuilt, probably in the last 30 years. I've had the oil pan off, it's very clean inside. I do know the theory about not switching to detergent oil, it can break crud free and clog oil passages. That's why piston aircraft engines don't use detergent oil.
Donny, I'm interested to hear more about why you recommend such heavy oil. Much heavier than the '77 manual calls for.

 

Just run the cheapest 10w30 you can get. Its still probably better than anything around 45 years ago.

 

Even though back then they were using "Pure Pennsylvania Crude" etc?

A lot of fancy engineering these days, in all fields, is to make up for poorer raw materials or to cut expense. I am not always convinced that newer is better.

 

I use whatever 10-40 is on sale at my FLAPS, usually store brand (napa).
These are tough engines. Any clean oil is better than dirty oil.
If no crud in pan, add a qt of atf, run 20-30 min,then change oil.

 

Run 30 WT Quaker State with A pint of STP. Have used this for 50 Years Plus with no problems.

 

Ok. I know we all like old stuff. I know we like antiques. We all agree that newer isn't always better, But..

Its not like you can go back in time and buy some 50 year old oil to run in you 50 year old engine..

And if poor raw materials are the reason why we run special synthetic oil in my truck, why do I have to do nothing but change the oil every 7500 miles to get better milage, at least twice the HP off the showroom floor and to run 300k miles with a gas engine? At 75K those old engines needed a rebuild or a wrecking yard.

Just saying.

 

Agree with above statement!

 

My plow jeep leaks oil so fast it's not worth buying new oil for it. I dump in the pure synthetic drain oil from our cars. It's fine. Dirty synthetic is still better than the oils that were available when this engine was new, IMO.