Before anybody attacks!! I have used the search function and it seems that it is so hit or miss so I would rather get a few direct opinions on the matter.

I'm wanting to run a little thicker oil in my Jeep. It has 211,xxx miles and has had conventional run in it it's whole life. Would it be a bad idea to start running Rotella T6 5w40? Would this hurt my engine more than help it? I have read the Bob the Oil Guy articles, so please do not post that. Just looking for first hand experiences.

Thanks guys.

 

lots of guys run the t6 in the 4.0

 

I've read that. I'm simply asking if anybody thinks it is a bad idea to switch to syn. this far in the engine's life.

 

Just run 10W30 and a quality filter and you'll be fine. Conventional or synthetic, doesn't really matter at this point.

You don't need a thicker oil or any additives. Why mess with success?

 

Very true. I'm having the common "check gauges" problem with my oil pressure reading. This happens only when I've been running the Jeep for a good bit. If it is just hitting hot idle its not as low. No knocking or any strange noises, and there doesn't appear to be a significant sludge problem. Gonna go ahead and say my sending unit is probably on its way out. Just definitely want to keep her healthy!!

 

If u've read the oil facts in the Motor Oil University article (and other factual motor oil articles) at BITOG and fully understood the motor oil facts vs myths, wouldn't asking what "anybody thinks" be kinda like saying "screw the facts, I want opinions"?

One way to keep her healthy is have the oil pressure verified with an accurate mechanical test gauge especially if u suspect a faulty dash gauge reading.

 

The problem is that I have a hard time deciphering a lot of that stuff. I just want to know what works for people.

 

Make sure to use a QUALITY filter such as WIX, do not use a Fram or STP filter. Wix is the only brand that makes their own filters, not a relabeled filter from another company.

 

I'm running valvoline max life 10w30 and one qt of Lucas. And a napa gold filter (same as wix). Does good. And on the synthetic oil if you have any oil seeps/leaks running synthetic will make it worse. The particles are smaller and will magnify the leaks/seeps

 

:wall:

 

BEFORE this thread explodes with "I run this" or "Full Syn is the Devil" or "EVERYTHING IS WAX BASED, DONT USE IT!", I will attempt to satisfy the OP's question. Btw, at the risk of seeming like a male organ, t6 and full syn usage have been covered before multiple times.

Anyways, I run T6 5W40 in my rig. I switched to a full syn 10w30 when I first bought my XJ with a tad over 190k miles. My engine didn't explode, no deals with the devil, and I didn't spring a bazillion leaks. The 4.0 gladly took the full syn. My most recent oil change with 206k miles was with the Rotella T6 5w40. Best oil I've used to date. Barely any cold start noise, and the 40 helped with hot engine noise and slightly less oil consumption. I love the 5w40. Also, AS MENTIONED, you MUST use a quality filter. Toss FRAM in the trash and light it on fire. IIRC, Wix/Napa Gold, Motorcraft, Puralator, and a few others are great. Most are made by the same companies anyways, like Wix and Napa. Our 4.0'S NEED a good anti-drainback valve since the filter is installed either stick up or sideways.

 

Btw I'm not saying synthetic oil will cause leaks, I'm only saying it will worsen leaks that are already present. I've seen it happen all the time. I'm gonna have to look into the t6 cause sounds like y'all have good feedback about it

 

I run high mileage oil along with a good filter. Have a 99 jeep sport 4x4, auto with o/d b& cruise with 159,122 miles. It appears as though PO didn't change any of the fluids, or do routine maintenance. All fluids from radiator to rear diff have been changed, including filters, with no leaks, or oil consumption. New track bar, ball joints, shocks, leaf springs, battery, and tires. Completely stock, since it's my daily driver, and only vehicle. Gas mileage sucks, but gets me to places where average person wouldn't go. I've heard that syn oil will break down the sludge that has built up over the years, and loosen up the engine. I've also heard the 4.0 is a very strong engine and will get 250 - 300 before needing to be overhauled. Is this a myth, does it depends on a lot of things, etc? Doesn't the use of a thicker oil depend on the climate your in? I live in Colorado, and the winters get very cold! Even though I'm 65, I'm a newbie, with limited mechanical abilities. So when it comes to Jeep ownership & 4 wheel drives, I'm somewhat lost/misinformed. Always had Toyota's or Subaru's in the past, all new, so any reliable information is appreciated.

 

Rotella is not a full synthetic, but merely a highly refined conventional oil that's allowed to be called synthetic by the government. It's still a good oil, however. It will work just fine in your jeep.

 

Thanks for the feedback guys. Good to hear that people have switched to the Rotella at high mileage.