The Best Oil for the 4.0: 30W vs 40W

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The Best Oil for the 4.0: 30W vs 40W

Post by 1bolt »

It looks like there's is no significant wear or reliability benefit to running heavier 40 weight oils in our engines compared to the lighter 30 weights. If you didn't already know; the prevailing opinion is that our I6 wears less and lasts longer with 40 weights (10W40, 5W40, 15W40 etc.) this seems to be the conventional wisdom especially on the number 1 motor oil site http://www.bobistheoilguy.com. Ask any expert on their forum and they will tell you the Jeep inline likes a 40w and especially with respect to iron wear, which its famous for high levels of. I used to pimp 20 weights, but such was the weight of opinion on BITOG that my last two fills were 10W40. This was probably one of the factors motivating me to take a hard look, I don't like following the herd without looking for my own evidence.

Instead of my usual long detailed preamble explaining all the mind numbing data harvesting and analysis I did to figure this out. I'm just stating it out front for anyone interested in the lowdown; but who just isn't as geeked up about the subject as I am. If you're wondering what a UOA is and how in the world I came up with these numbers keep reading, after the colorful pictures :mrgreen: .

First the numbers
Image
The Above are straight averages, in others words total wear metal numbers for each type of metal (in PPM) divided by the number UOA's irregardless of average miles per UOA. Below are adjusted averages, where the number of samples was balanced to arrive at a similar amount of miles per UOA (throwing out the highest and lowest mileage samples) then dividing the wear metals by the number of samples.
Image

These two show you a gross average of what each UOA looked like. I tried running the metals divided by only mileage but had a hard time coming up with meaningful numbers dividing hundreds of thousands of miles into a couple hundred parts per million (no math wiz here that's for sure).

The opinion I've formed is that there's no sense in running 40w oils. lighter 30w's will improve power and gas mileage slightly. And from the looks of things will provide the same level of protection, they will get to parts quicker on cold starts and they will stay on parts longer when parked. This may be reflected in the slightly higher bearing metals seen in the 40w column (copper and lead).

I really thought I was going to find a significant deviation from one weight to the other, but these numbers are small enough to be called insignificant. If anything, 30 weights might be showing a tiny edge in performance over the heavier oil. One thing is clear, neither oil significantly lowers Iron wear over the other.

This started off as an attempt to study ZDDP and Oil weight as it effects our 4.0's and strokers. By surveying published UOA's (Used Oil Analysis) from BITOG (BobIsTheOilGuy.com). I started searching there last year and compiled all the UOA's I could find into Excel; that involved strictly the Jeep Inline 6. It took some serious carpal tunnel inducing search marathons to dig up every reference to Jeep inline 6's I could find that involved someone posting their UOA. This involved hundreds of thousands of miles of oil changes (317,778) from a crap load of UOA's, spanning 5 years of the BITOG forum (that's as far back as you can search). Included is just about every viscosity of 30w 0W30 on up to 10W30 and 0w40 on up to 15W40.

I threw out any UOA's showing obvious signs of shot bearings. Or new engines that were obviously showing massive break in metals. This comprised at least a dozen or more UOA's showing abnormally high levels of copper and lead. At least two UOA's thrown out due to either a cracked 0331 head or a blown HG (extremely high levels of coolant cantaminating the oil). A few dozen were weeded out due to unintelligible formatting or for lacking all important info like miles on the oil, or viscosity, or exactly what engine the Jeep had. I also didn't use any info from the 4 banger UOA's... they have 2 less cylinders thus their wear metal numbers will be lower. I didn't feel that mutiplying by a 3rd would be accurate.

One bit of errata Mobil 1 (straight Super Syn M1) consistently shows higher levels of Iron than any other Oil... regardless of viscosity. I have two theorys here: straight M1 is a PAO ester based synthetic (as I understand it) esters are extremely good solvents... the esters melt away trapped sludge and grime more so than other oils releasing trapped wear metals. There's some creadence to this, as there are actual expensive Engine treatment systems (AutoRX) that use pure esters to clean out neglected engines. Or #2 M1 also consistently shows lower Phos and Zinc (ZDDP) levels sometimes lower than even current API low ZDDP oils. Which could lead to more valve train wear.

I am a fan of M1, but I use High Mileage which has very good Phos and Zinc levels (old SJ spec) but I am planing on sending out a sample to Blackstone of my current fill (10W40 M1 High Mileage) to see if I don't need to re-evaluate my choosen oil. One thing I'm pretty sure of, I will be going to a 30w next change. Whether it will be M1 High Mileage 10W30 or not is the question. But that's pretty much the only game in town for a high ZDDP off the shelf high quality oil that is also a 30 weight... (oh and not a racing oil)

Maybe that's a different subject entirely but When you've looked at as many UOA's as I needed to to put these numbers together, there's VERY few oils that have zinc and Phosphorus levels above the 10% (1000PPM) target. Even in 2003 there were almost NO oils left that were still in the right ballpark.

No real 20w UOA's were found, and no 15W50 UOA's...

Deisel grade Oils (Delvac and Rottela) did not jump out at me as having better wear numbers. Just as low ZDDP and high ZDDP haven't immediately jumped out at me for better or worse wear numbers. I will have to crunch those numbers, but I expect nothing shocking or particularly enlightening, if only because the 40w's on average have better ZDDP (due almost entirely to the Diesel oils all being 40 weight) but not apparently better wear numbers.

Still At some point I will correlate all these UOA's against ZDDP levels and see if there are any significant trends. Look for that post here later.
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by John »

That is a fine study on the oils, have to agree the 10w 30 is showing a slight edge if you look at the bearing metals content. Kinda jumps out at you. The iron numbers are difficult to assess, as you pointed out the cleansing with mobil one is one of it's traits. (Have ran it in my 99TJ since day one). Let's also recognize we operate these jeep engines quite differently etc. I have to encourage your study..
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by gmakra »

Great post, it refreshing to see others looking at oil analysis. I have used this tech on and off thru out the years for industrial equipment. And in light of the changing landscape of lubrication it great to see the research.
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by Flash »

Rock on dude!!!!!!!!!!!!

Like the intensity of your search, and the care of you date :cheers:


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Re: The Best Oil for the 4.0: 30W vs 40W

Post by jeepinwi »

Your findings definitely show light in the end of the tunnel for all the cam failures. Once the oil situation is figured out, I think we can safely run any cam we choose in our I6. Maybe I got a good cam, maybe it's the oil I'm using, but I have about 24,000 miles on my stroker, and all is well. My notorious Crane 753905 cam had nearly zero wear at 20,000 miles. I think the only thing consistant with my oil changes is I have used a 40 weight oil everytime. For a while, it was a cheap farm-grade 10w40 oil, now I'm using Rotella T 5w40 synthetic.

I'm really a believer in the farm-grade oil. If that oil is designed for tractors with 50+ year old engines, it should also work on our similarly designed I6 engines. Best of all, the oil is only $13 for 2 gallons.
99 Cherokee SE - 2 door, 4x4, 4.6L stroker, 5 speed, 8.25 rear, 60mm TB, stock exhaust
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by Muad'Dib »

I run 15w50 M1 Extended Performance. I dont have any leaks or any "serious" problems from what i can tell. I do however have alot of top end noise. It almost sounds like serious rocker arm chatter.

Ive shrugged it off for a long time now, and recently i have wondered if my oil has anything to do with it or if i need to be replacing parts. From what i can tell (and from what i have heard) the Mobil 1 Synthetic 15w50 "Extended Performance" is the best oil for our I6. Mobil even states its designed for flat tappet cams, and it has 1200 ZDDP.
You have seen their Product Guide right?
http://www.mobiloil.com/USA-English/Mot ... _Guide.pdf

I would advise Extended Performance M1 instead of the High Mileage which really isnt IMO the best M1 Oil to be using in our I6's...

Now what im really getting at is im wondering to myself if im runnng the right oil viscosity. I think of something like 15w50 being pretty thick... but then again isnt it a multi-viscosity oil? So technically arent i more protected when the engine gets really hot compared to say 10w30?
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by 1bolt »

Take this as just my opinion but if you are willing to give me a little benefit of the doubt for a minute, and realize I've just finished filtering through somewhere close to a hundred different labratory analysis' of used motor oil:
You can take this at face value M1 HM, M1 Delvac, and Rottela T are just about the ONLY off the shelf (available in common stores) motor oils that have over the %10 ZDDP target.

Two of those are hard to find in anything less than 15W40, and Rottela has recently changed and has lowered Phos and Zinc

M1 High Mileage "on paper" is the best available off the shelf oil to put in our engines. I wouldn't pimp it so much if I wasn't convinced of that. Of 10W30 and 40 Gasoline motor oils (that are commonly available) it has more Calcium, Phosphorus and Zinc than anything else I've seen a VOA for. (Virgin Oil Analysis) including M1 EP. In addition it is not an overly thick deisel 40 weight such as 15W40. It has somewhat less ZDDP and calcium then those diesel oils, without the power robbing excessive viscosity.

Of course this is "on paper" as I don't have any UOA's for Jeep inlines using M1 HM. If my UOA's show different I will be the first to eat my words and re-evaluate. I have four sample bottles from Blackstone, and M1 HM fills in 3 Jeeps and one Mustang.

First and foremost I am interested in Oil that protects my Jeeps, with a YJ, a stroked XJ, a family XJ and a Work MJ all with 4.0 family engines, I have a vested interest in their longevity and I wont let marketing hype or the weight of opinion on BITOG keep me from using the best financially sensible oil for my little fleet o' Jeeps... (Read: no racing oil or $20 per change ZDDP supliments) I also have a 1965 Mustang with a flat tappet valve train 289 V8 that is very low miles; rebuilt in the 80's before anyone ever heard of ZDDP... you can bet I'm not interested in anything but the best for it, especially because it's not had a decade + and 100k miles of ZDDP protection built up on the cam lobes, like most of our old 4.0's have, during the slow phase out of ZDDP.

Also just my opinion but 15W50 is needless overkill... Personally the heaviest oil I would use is 0W40 to 10W40... One theoretical problem with a 50w is starving your bearings during startup. Its thicker and takes longer to pump into the tighter clearances. You are also wasting horse power and torque due to elevated oil pressure... As a rule of thumb for every pound of oil pressure an engine looses half a hp and foot pound. The thicker an oil is, the harder your engine has to work to pump it around, which means you're also losing mileage as well.

I've seen Dyno shootouts where 10hp and pound feet were lost just from the differences between 10w40 dino and a synthetic 30w. I'd hate to guess what a 50w is robbing from your engine.

With 40 weights showing no wear related benefit, I have serious doubts that 50w would fair any better... And I suspect 50w would exibit higher bearing wear at startup and especially in cold weather.

I will try to dig up the VOA numbers for M1 High Mileage but very few oils come anywhere close to its calcium and ZDDP levels.
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by 1bolt »

http://www.bobistheoilguy.com/forums/ub ... Post985660


Virgin analysis of M1 HM. It's SL rated and a good 300 to 400 PPM more Phos and Zinc than current API spec oils. 900+ Phos and 1000+ Zinc compared to typical numbers for current API specs in the 600 to 700 range for Phos and 600 to 800 for Zinc.
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by Muad'Dib »

Im not trying to dog ojn you at all, im just sharing what i have learned and seeing if the information im retaining is complete BS so that maybe i can learn something. Thats also the reason why i asked a few questions..


So the bottom line is your saying M1 HM 10w30 or 10w40 right? 10w30 leaning more towards the "performance" application and 40 towards a little bit more safety.

The reason why you dont really evaluate EP yourself is because its too viscious..

Am i understanding you correctly?
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by 1bolt »

Yeah EP is just too thick for me so I didn't look too hard at it. Just like Delvac and Rottela T. I haven't seen a VOA of it recently either. Not trying to say my way is the only way, it's just what I'm convinced is best for my own use. As I said I could be completely off base myself we'll see after I get some UOA's done. I was convinced that 5W20 was the shiz for most of the XJ's life as a Stroker, until all the constant repetition on BITOG finally got me thinking I needed a 40 weight. If I can find a 5W20 or 10W20 with nearly 1000PPM Phos and 10000PPM Zinc, that also wasn't a racing oil, or overly expensive I would go right back to 20 weight at this point.

But then I know my oil clearances were nice, and I'm not afraid of light oil especially if its a PAO synthetic like most M1 products. Problem is straight M1 5W20 has only around 700PPM and 800PPM of Phos and Zinc respectively.

Anyway I don't think you're retaining BS, lots of people swear by heavy oils, I just don't think there's any need... its not going to make your rig grenade prematurely, but its not doing your fuel economy or horse power any favors either.

Thanks for the comments you all. More then a couple times while inputing data in Excel, scouring hundreds of search results and typing that book of a post; I asked myself if the info would even be interesting to anyone else but me.
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http://www.jeepstrokers.com 94 XJ Stroked lifted locked. 89 MJ restored Work truck, 88 YJ going on third build up and second Stroker.
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Re: The Best Oil for the 4.0: 30W vs 40W

Post by Backwoods Rambler »

Any updated UOA's?
1bolt wrote: But then I know my oil clearances were nice, and I'm not afraid of light oil especially if its a PAO synthetic like most M1 products. Problem is straight M1 5W20 has only around 700PPM and 800PPM of Phos and Zinc respectively.
I thought that (According to the GM tech article posted) in a previous thread an oil with .08% (800ppm) is sufficient for flat tappet engine such as ours, did I mis-read that??

1bolt wrote: Thanks for the comments you all. More then a couple times while inputing data in Excel, scouring hundreds of search results and typing that book of a post; I asked myself if the info would even be interesting to anyone else but me.
I've been there brother :cheers: My wife thinks I'm crazy spending my nights pouring over document after document just to find the best oil filter. I settled on the NAPA Gold 1515 btw. It's not THE best, but it's a great deal for it's high build quality and fair price.


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Re: The Best Oil for the 4.0: 30W vs 40W

Post by Muad'Dib »

It was oil change time last weekend, so i tried a lighter weight oil (plus its a good idea with Winter coming)... M1 EP 10W30
My Girlfriend and the Kids took a trip over into the valley (west Oregon) and visted some family and did a Wildlife Safari (it was AWESOME).

At first i didnt notice much difference.

The first thing i noticed was that oil pressure when hot got down to about 18-20.

Then i noticed that my Jeep had WAY more pep to it than it has lately. Just more put you back into your seat power.

I also started noticing that my chatter noise has been cut in half. Its still there, but its definetly not as loud on start up.

Lastly, Gas mileage has seen a HUGE increase... At least so far.. but then again i have done ALOT of highway miles. I will know more in a couple weeks with all my to work and back driving!
If it feels right, then STROKE it!
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