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Discussion Starter · #1 ·
I know the owners manual recommends the use of 5w-20 for our beasts. Thats what I have always used. Recently, I was told, that I should be using an oil with with a higher viscosity irregardless of what the manual says. This particular mechanic recommended at least a 10w-30, but that 10w-40 would be the best for engine life. Is this true? Anyone out there using oil of this viscosity?
 

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Incorrect. Viscosity is a tricky thing.

Unless you drive in one of the hottest climates in the country/world (AZ, NM, Baghdad, etc.), you should stick with 5w20, the manufacturer's spec.

Yes, you can modify the game plan and change this, and you may not realize immediate changes, but there are a lot of factors that go into a manufacturer's specification for oil viscosity:

* Thermal break-down
* Circulation speed
* Engine block/Cylinder sleeve material
* Rotational mass of engine components
* And many others...

In my opinion, and after having built engines for years, I would recommend 5w20, and would highly recommend a full synthetic oil (like Mobil 1) for maximum oil and engine life.

One point of mention regarding synthetic oil use. Even if the synthetic oil manufacturer states you can go 5k, 7.5k, or 10k, without an oil change, that you still need to change your oil filter every 2.5k-3k miles, as the filtering properties of the oil filter are not extended due to the use of a better oil. If you don't, the filter will allow dirt, etc. through to contaminate the oil, and will cause premature engine wear.

Hope this helps.

RC
 

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Discussion Starter · #4 ·
Yes, but isnt it true that a more water based oil ie 5w-20, will not fully lubricate the engine parts as well as say a 10w-30 , would?
 

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Yes, but isnt it true that a more water based oil ie 5w-20, will not fully lubricate the engine parts as well as say a 10w-30 , would?
Not necessarily. "Lubricate" is unfortunately a vague word. It could mean how quickly the oil lubricates, or how thoroughly it lubricates. It also has to do with the full cycle of the time it takes to pump the oil from the pan, throughout the engine (including valve train), before being gravity/pressure fed back down the oil pan to start the cycle I over.

Example:

If I use a 40 or 50 weight oil, it's characteristics for lubricating "thoroughly" and for an extended period as it passes through the engine, you could say it is better. Well that depends on components in the engine, and how long the engineers designed the oil pump and system to lubricate the motor per RPM, and for a full cycle. 40 or 50 is thicker, and arguably more durable, but if 40 or 50 can't make it back to the bottom of your oil pan in the intended period of time, then "lubrication" has not been adequately achieved.

For vehicles with smaller displacement engines, typically lighter weight oil is used, because of the rotational mass, and oil cycle time. For vehicles with larger displacement engines, heavier weight oil is typically used, again because of an increased rotational mass, and oil cycle time. (Rest assured, that when I upgrade my 3.8L V-6 to a HEMI) that I'll be running a higher viscosity oil, due to the things discussed above). :D

I hope I haven't confused anyone, and that this helps!

Happy Thanksgiving!

RC
 

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irregardless
unpossible:D

I've been running 5w30 for a while now. The Export Jeeps with the same 3.8 have been running it since day one so I have no problem with it.;)

I run 4500 mile changes. Any longer than that and the oil was dark and watery with the 5w20 even though the manual calls for 6k changes. Since switching to 5w30 the oil looks what I consider normal all the way to the end even if I run over a few hundred miles.

longevity? well see, just passed 104k and it was running fine yesterday.:beer:
 

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Jeep specifies the 5w-20 in North American markets for emissions compliance reasons. Read the manual carefully and you'll see that it says 5w-30 is "acceptable". I guess it is, because it's specified everywhere else. The lighter oil is probably ok in winter conditions, but as hot as that thing runs, particularly in higher ambients it's no wonder we read about high oil consumption & short engine life on some JKs.

Setting the oil change interval at 6k miles in this day & age is something of a tip-off that somethings not kosher with the engine/vehicle combination in the first place, as that would mostly qualify as a "severe duty" service interval with any other manufacturer. Having a tech & manufacturer service exec. background I know how these decisions are made, right or wrong. The 3.8 was a bad choice for the JK from the get go, but as they say, it is what it is and you have to accept the thing's needs. Plenty of reports of them going 150k+ miles with good service and care, so not like it's going to take a dump on you at 60k miles like a '65 VW.
 

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Discussion Starter · #8 ·
So should I stick with the 5w-20 or go with a higher viscosity?
 

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Been running 5w30 oil comes out looking alot better at 3500-5k also no consumption issues..09 motor with 20k
 

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I've always had diesel pickups, which use 15-40, so knowing these 3.8s aren't known for longevity I've been using the same. I have no issues with cold starts. Seems to run smoother.
 

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Discussion Starter · #12 ·
Which article are you referring to on that page? There are three.
 

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I live in one of the hottest climates in the world, Imperial County, California. The local dealers in El Centro and Yuma, AZ both recommend 5W20. They do not recommend any of the 30 multiweights. I have stayed with their recommendations and have not had oil issues. I am using 1/2 quart every 4000 miles. That is fine.
 

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I ran 5w-30 in Las Vegas, it gets a little warm there as well, zero problems/consumption. Still run it here in Texas.
 

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I just joined the 5w30 club too, due to consumption issues with the 5w20 that got gradually worse - and then skyrocketed around 50K. Haven't done an oil change since switching, but the engine is much quieter now (no clattering). Feels better too - but I think that's in my head ;)
 
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