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Old 11-29-2009, 12:29 AM   #1
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Oil weight question.

Right, so most of you guys probably know that I bought a used 09 X a couple of months ago. Today, I took her in for an oil change. I always buy my own oil and filter and bring them with me. I have the 3.8, brought Mobil1 5W30, and the dude told me I was using the wrong weight, that I should be using
5W20. Um.... I never even heard of this weight before. So what's the deal? I live in Middle Tennessee, we don't really have extreme heat or cold, is there that big a difference in the 5W30 and 5W20?

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Old 11-29-2009, 06:31 AM   #2
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The engine is set to run on 5w-20; did yours come with a manual? If not, you can download the pdf from the Jeep website.

Some engines won't flow enough oil if you use a higher viscosity oil than it was built for. The galleys and passages back-up and something will pop (usually the oil filter).
Not sure if this will happen with the 3.8, but there is no downside to running the proper oil; so why not?

I use Mobil-1 0w-20, btw.

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Old 11-29-2009, 08:20 AM   #3
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Mobil makes a 5w20. I always use Mobil products, specifically 10w30 and 10w40 Mobil 5000. I have used the same oil in everything I have ever owned. I took my 08 Bullitt Mustang to get an oil change before I got the JK, and the grease monkey told me the same thing (the car called for 5w20), and I got majorly pissed off... I'm gonna 5w20 Mobil on my next oil change with Mobil 1 oil filter.
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Old 11-29-2009, 03:39 PM   #4
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I was surprised to see this as well. I was told the engine was designed to run the light weight oil for a 1% increase in fuel economy. Seems pointless to me but if the engine was designed to run lightweight oil thats what I will use.
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Old 11-29-2009, 04:08 PM   #5
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I was surprised to see this as well. I was told the engine was designed to run the light weight oil for a 1% increase in fuel economy. Seems pointless to me but if the engine was designed to run lightweight oil thats what I will use.
It's not a light weight oil; it's a very slippery lubricant full of technology.
The engineering that goes into today's oil is incredible. One of the GC/MS units that Exxon/Mobil uses is over a quarter million dollars.
It's just a runnier viscosity; it flows faster.
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Old 11-29-2009, 05:48 PM   #6
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Originally Posted by WranglerX2009 View Post
Right, so most of you guys probably know that I bought a used 09 X a couple of months ago. Today, I took her in for an oil change. I always buy my own oil and filter and bring them with me. I have the 3.8, brought Mobil1 5W30, and the dude told me I was using the wrong weight, that I should be using
5W20. Um.... I never even heard of this weight before. So what's the deal? I live in Middle Tennessee, we don't really have extreme heat or cold, is there that big a difference in the 5W30 and 5W20?
How much oil did you bring? If you didn't know the correct viscosity, chances are you didn't know it takes 6 qts. either.
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Old 11-29-2009, 06:53 PM   #7
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The engine is set to run on 5w-20; did yours come with a manual? If not, you can download the pdf from the Jeep website.

Some engines won't flow enough oil if you use a higher viscosity oil than it was built for. The galleys and passages back-up and something will pop (usually the oil filter).
Not sure if this will happen with the 3.8, but there is no downside to running the proper oil; so why not?

I use Mobil-1 0w-20, btw.
I have had the dealership change the oil twice now. Both times they used 5W30. I havent checked the owner's manual yet, but I would hope that the dealership knows the appropriate oil for the vehicles they sell/service!
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Old 11-29-2009, 08:17 PM   #8
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How much oil did you bring? If you didn't know the correct viscosity, chances are you didn't know it takes 6 qts. either.
Actually, I bought 6 quarts.
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Old 11-29-2009, 08:52 PM   #9
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You know it says 5W-20 right on the oil filler cap. I'm about to do my 3rd oil change. I've been doing the standard 3000 mile oil changes. Anyone else go for longer?
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Old 11-29-2009, 10:11 PM   #10
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When I use Mobil 1 and a Mobil 1 filter, I will change it somewhere around 5k miles...the old oil always still looks and smells good. But if I use Mobil 5000 I change it at 3k miles. Mobil 1 is some good stuff, but a bit pricey!!!
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Old 11-30-2009, 07:27 AM   #11
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You know it says 5W-20 right on the oil filler cap. I'm about to do my 3rd oil change. I've been doing the standard 3000 mile oil changes. Anyone else go for longer?
I change it every 6K. I'd only change it sooner if you run in very dusty conditions, have a CAI with gauze filter media, or wheel hard in severe heat.



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I have had the dealership change the oil twice now. Both times they used 5W30. I havent checked the owner's manual yet, but I would hope that the dealership knows the appropriate oil for the vehicles they sell/service!
Counting on a dealership to do the right thing is not advisable...



Exxon/Mobil, Shell, Chevron --- their oil engineers all train in my lab. The 3.8 was designed to achieve correct flow dynamics and oil pressure with 5w-20. It's not a '69 396 Chevy engine; it doesn't need help from viscosity to close sloppy tolerances...
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Old 11-30-2009, 07:59 AM   #12
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OK. I'm coming up on my first 3,000 mile oil change. I have to decide which way to go. Full syn, blend or traditional? What is the big advantage one way or the other. Big price differential to go synthetic. Any big difference between the synthetics? I hear lots of folks mention Mobil 1, but what about some of the others like Castrol?

I fully expect to get lots of opinions, just looking for a good reason to use the high $$$ oils versus the more traditional oil. Seems like you can pay for a lot of oil changes going with a traditional oil.
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Old 11-30-2009, 08:06 AM   #13
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i change my oil at 5000 running castrol full synthetic and a fram filter. my wifes rubi is a daily driver and a street ride. the most dirt it sees is an occasional dirt road at camp. same goes for my 4runner .
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Old 11-30-2009, 08:09 AM   #14
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Most of today's "synthetics" are actually just highly refined dino juice that meet the performance criteria of true synthetics and have earned the right (Mobil vs Castrol court decision) to be labeled "synthetic".
Chevron invented the process, btw.

Mobil-1, after years of being a true synthetic, finally caved-in to economic pressures and changed their devil's brew to a mixture of dino and synthetic stocks. They still offer pure syn in the bottles with gold caps.

Want a real synthetic?
Try Amsoil or Redline.

Want a hydrocracked dino pseudo-synthetic?
There's Mobil-1, Castrol, Royal Purple, and a product from every company on the planet.

Can your Jeep tell the difference?
Not likely.

Today's oils are very well designed to provide wear protection, suspend grit, dissipate heat, and prevent corrosion. Any oil that's engineered to be a certified as a 5w-20 will certainly protect your Wrangler for 6000 miles under almost any North American condition.
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Old 11-30-2009, 09:39 AM   #15
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the only reason to change the oil in your engine is because it gets dirty or breaks down, and the oil will get dirty long before it breaks down. thats why engines today can go longer between oil changes because they are designed better and dont allow the oil to get dirty near as quickly as they used to. just FYI. and you wont damage the engine with 30 but it was designed to run on 20... and i dont see any reason to run full synthetic IMO but there are arguements for it, i just dont worry about it that much, all oil now a days has additives to improve it...

though i wish full synthetic was cheaper to make because then we wouldnt have to rely on fossil fuels atleast for that one aspect...
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Old 11-30-2009, 11:46 AM   #16
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Good info guys. Think maybe just a good oil not necessarily synthetic makes sense and just change it on a reasonable schedule and use good filters.

BTW - what filters are folks using? I live in a swamp, but we get lots of sand/dust.
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Old 11-30-2009, 11:58 AM   #17
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BTW - what filters are folks using? I live in a swamp, but we get lots of sand/dust.
I use either the Mopar, Bosch, or Mobil-1 filter. I think they all come from the same factory.
I usually get the Mobil-1 filter for free when I buy oil; 6 quarts for the price of 5 and a free filter if I flirt with the sales girl...
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Old 11-30-2009, 12:00 PM   #18
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there arent any pretty girls at the parts stores i go too here in cleveland, aka podunk TN
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Old 11-30-2009, 12:04 PM   #19
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there arent any pretty girls at the parts stores i go too here in cleveland, aka podunk TN
Do you think the girls in podunk Canton, GA are any prettier? I didn't say I flirted with a pretty cashier... ...cowboy up and go hoggin'.
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Old 11-30-2009, 12:30 PM   #20
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lmao!
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Old 11-30-2009, 02:36 PM   #21
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Maybe here in Savannah I might have more luck. But, it is an auto parts store. Maybe not.
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Old 11-30-2009, 02:45 PM   #22
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you might be better if you took a smokin hot girl WITH you and had her flirt with the cashier dudes now to find a smokin hot girl... other than my wife of course (she would never do something like that ;-))
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Old 11-30-2009, 06:45 PM   #23
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I change it every 6K. I'd only change it sooner if you run in very dusty conditions, have a CAI with gauze filter media, or wheel hard in severe heat.



Counting on a dealership to do the right thing is not advisable...



Exxon/Mobil, Shell, Chevron --- their oil engineers all train in my lab. The 3.8 was designed to achieve correct flow dynamics and oil pressure with 5w-20. It's not a '69 396 Chevy engine; it doesn't need help from viscosity to close sloppy tolerances...
Wow, someone actually read the manual!!!!
and the manual's recommendation is for regular oil. Of course here in the good ole USA, because everyone is so afraid to be sued, the recommendation for synthetic oil is the same as for dino oil.

Personally I use full synth (usually Mobil 1) and change ever 10K, I have done this on every car or truck I have had since the 80s and never had a problem. My son is still driving an old Civic I bought new in 89. It now has over a 150k on it.
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Old 11-30-2009, 06:50 PM   #24
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though i wish full synthetic was cheaper to make because then we wouldnt have to rely on fossil fuels atleast for that one aspect...
Actually all the synthetics out today are still made from crude oil. They are either made from Hydrocracked crude oil like Castrol Syntec, or from petroleum based PAO stock like Amsoil.

It is true athat PAO stock does not have to come from petroleum and can actually be created from other sources, but so far no other sources are as cheap.
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Old 11-30-2009, 08:20 PM   #25
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Yes I know Jeep says to run 5w-20 year round but common sense tells me not to, and since they didn't buy this particalar Jeep I win.

This common sense brought on by 30 years as an auto tech
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Old 11-30-2009, 11:51 PM   #26
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I use Schaeffer's 5w-20, 5w-30 or 10W-30 in all my vehicles. The Jeep also has Schaeffer's in the trans, transfer & diffs. Schaeffer's is full synthetic, go to web site to find a local dealer. It costs more than regular oil, but is less expensive than Moble -1, Castrol Syn, etc. I NEVER use Fram filters, period! I use Wix filters.
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Old 12-01-2009, 12:55 PM   #27
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Yes I know Jeep says to run 5w-20 year round but common sense tells me not to, and since they didn't buy this particalar Jeep I win.

This common sense brought on by 30 years as an auto tech
Who will pay for your new engine when common sense seizes it up? After all, since Chrysler didn't buy your jeep, you did, does Chrysler still get forced to pay for the replacement when you didn't follow their recommendation on oil weight?

I use standard oil. It is changed every 6K according to the owner's manual. I will likely drive it until it rots out from under me, or is totaled (God forbid) in an accident. I have traded most of my past vehicles in between 100k and 175k miles. This one may out pace my others considerably. Most likely on one engine I hope. The resale value when I decide to get rid of it will not change regardless of what type of oil I put in it. Most people who drive a jeep just want the thing to run and owe them nothing when they are done with it. Following the owners manual recommendation with respect to oil changes will accomplish that. Why do more? I speak from experience owning various cars and now the jeep in 30+ years of driving. None of them got anything special regards to PM and none of them really owed me anything upon disposal of them. My other cars all got the longer interval recommended oil changes. It didn't subtract from the resale either. Take it from experience, follow the service recommendations carefully and don't listen to the dealer who will gladly over service your vehicles for you. I like to KISS with respect to the running of a vehicle. So...keep it simple and enjoy its features.
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Old 12-02-2009, 10:05 PM   #28
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Whoa there.. ease up a bit.

There USED to be a temp chart in owners manuals listing which weight oils to use during certain outside temps.

MOST manuals still say to change spark plugs at 30K miles like the old points ignition days.

If using a 10w oil seizes the engine I don't think I have a problem, Chrysler has a problem.

I use 10w-30 castrol synthetic (only cause we now carry Castrol.... free for me)
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Old 12-02-2009, 10:21 PM   #29
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I would say that it is a lot easier using the suggested weight oil rather than hiring a lawyer to go after Chrysler to correct their way of thinking about their suggestions about what to do for your engine is. I'm just speculating. Could be you'll never have a problem. While they are paying for my engine replacement I plan to follow what they say.
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Old 12-03-2009, 06:52 AM   #30
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If you're a real gear-head and have the shop & tools at your disposal, Ockgator, install a gauge and see what the oil pressure is with a 10w-30 vs a 5w-20.
I know some Ferrari guys that switched to 0w-10 after doing a similar exercise.

There is no "common sense" when it comes to applicable motor oil viscosity; there is only measurable data based upon flow dynamics and oil pressure. This isn't an emotional decision like tire choice and you can't base your choice upon criteria from other vehicles and/or engines...

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