Prefered synthetic oil for 4.0?

Almost everyone runs conventional. In really cold weather, as you may see, a synthetic might be preferable. Doesn’t matter what kind.
 
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I run 1 qt synth, the rest dino oil. That way I actually know how much synth is in the engine. All Valvoline. If you buy the 'synth blend' you have no idea what the ratio really is. I truly doubt I'm doing the engine any real favor adding the synth oil. It has become a habit for years. You would be better off saving the synth oil for where it is actually better. Air cooled engines like lawnmowers and log splitters.
 
how long in between oil changes with conventional vs synthetic?
is the 4.0 different than any other v6 in that regard? obviously keeping in mind all the different factors playing into how and where the jeep is driven...
 
how long in between oil changes with conventional vs synthetic?
is the 4.0 different than any other v6 in that regard? obviously keeping in mind all the different factors playing into how and where the jeep is driven...


Regardless of type or miles I change it every 3 months, usually 2000-3000miles. Oil breaks down with heat, so i take into account all the time the jeep is on and not moving. i used to be an aircraft mechanic and all the service intervals are a function of time.
 
I thought I've heard somewhere that once you go from conventional to synthetic, you're not supposed to go back. Is that true?
 
This topic has been beat to death and additionally unloaded with a 30 round mag into it, on every car forum.
Answers will range from what ever is on the shell in the store, to some mystical aircraft-grade science that needs to be changed every few weeks.

Cheap oil will not make your engine kaput below 200k mile, and expensive rocket science will not push it past 300k.
Odds of you making it that far before losing interest in TJ or some other non-oil-related-shit failing are slim to none.

It has been proven time and time after in every application, parts made to proper specs will last its predicted life cycle. Shit show starts when quality control is ignored or manufacturer starts to cut corners.

Proper oil type and oil change intervals, it is that simple.
 
how long in between oil changes with conventional vs synthetic?
is the 4.0 different than any other v6 in that regard? obviously keeping in mind all the different factors playing into how and where the jeep is driven...

I stick with Pennzoil high mileage and change every 6 months(about 4k miles/change). Pennzoil high mileage has additives/conditioners that help seals from leaking.

They usually have rebates going on.

https://www.pennzoil.com/en_us/promotions/do-it-yourself-oil-change.html
 
I run 1 qt synth, the rest dino oil. That way I actually know how much synth is in the engine. All Valvoline. If you buy the 'synth blend' you have no idea what the ratio really is. I truly doubt I'm doing the engine any real favor adding the synth oil. It has become a habit for years. You would be better off saving the synth oil for where it is actually better. Air cooled engines like lawnmowers and log splitters.

I've typically used high mileage synth blend, but you make a good point. I think I'll switch to dino with 1 qt of full synth.

I used to run straight dino and change at 3k miles. It was fine of course, but noticeably darker than when it went in. When I switched to Castrol GTX synth blend and changed at 5k miles it looked like brand new oil. Went to 7k between changes and that seems to be the sweet spot.

That sold me on synth blend. I personally wouldn't run full synth in an older, high mileage engine that didn't come with it from the factory.
 
After 40 years of driving over 30 different vehicles and not one single oil related failure and never having run synthetic oil with any regularity I see no need to start now.
 
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I use Castrol 10/30 dino oil, because I have generally used that brand for decades. I have no way of knowing if one brand is better than another. If I couldn't get Castrol I'd buy a name brand oil of the same weight and not be concerned in the slightest. Proper operation and maintenance is what counts. Any other hype is a sales pitch. Synthetic oil is perhaps better at extreme low temperatures. My Jeep is a toy, pleasure vehicle and hobby. I over maintain it for the shear joy and satisfaction of twisting a wrench. I have an old Ford truck with a 460. I change the oil once a year because that is how often I am in America. Doubt it moves more than 500 miles.
 
I use Castrol 10/30 dino oil, because I have generally used that brand for decades. I have no way of knowing if one brand is better than another. If I couldn't get Castrol I'd buy a name brand oil of the same weight and not be concerned in the slightest. Proper operation and maintenance is what counts. Any other hype is a sales pitch. Synthetic oil is perhaps better at extreme low temperatures. My Jeep is a toy, pleasure vehicle and hobby. I over maintain it for the shear joy and satisfaction of twisting a wrench. I have an old Ford truck with a 460. I change the oil once a year because that is how often I am in America. Doubt it moves more than 500 miles.
My feelings exactly, though I use Valvoline. 55 years of driving with never an engine falure which I attribute to nothing more than changing the oil and filter at appropriate intervals, typically every 5k miles.
 
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If Valvoline is on sale, I buy Valvoline, if Castrol is on sale, I buy Castrol, etc...etc...and I get a Fram Tough Guard Oil Filter and call it a day. Every 5,000 miles. Dino oil all the way.
 

Because synthetic tends to clean everything real good in there, and on older engines that's not always a good thing. Can find it's way around seals that dino oil and a bit of sludge would not leak through.

I know there's endless arguments about that, but I've experienced it first hand.

That, and unless you have a high performance engine that strongly recommends or requires full synth from day 1, there's no real advantage to running it.
 
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