RocketMouse

Hi all....

*THIS IS NOT AN OIL THREAD...but a part design/manufacturing question*

The only question that I'm looking to get answered by someone that knows what they are talking about is the following....
I have heard that earlier years of the 4.0 (even though I believe all years were flat tappet lifter design)... that they required or was recommended for cam life to use an oil that had a higher zinc content. Whereas I have also heard that later model year 4.0s say '97 and newer did NOT require the extra zinc to protect the cam from premature wear, and that in those years of 4.0 the extra zinc could actual do more harm than good.

Can anyone truly help me get to the bottom of that. Were the later year 4.0s cams/lifters actually manufactured differently than the earlier years making them NOT require it?

Thanks!

00t444e

As far as I know all of the 4.0s were the same internally, aside from a few small differences, none of which would change the oil requiremens.They changed recommendation on later engines mainly because of emissions.

fb97xj1

AFAIK, the 4.0L has always used a flat tappet cam, and for years i have been told that flat tappets need the added zinc, which serves as a lubricant. A hydraulic roller on the other hand, like the 5.0L in my Mustang, does not need it.

dave1123

ALL engines with flat tappet lifters require a compound with zinc in it to reduce wear on the sliding surfaces where the lifters rub on the cam lobes. It seems a lot of newer engines use roller tappets so don't need zinc. The main problem with the current zinc compound (ZDDP) is it's combined with phosphorus, which can harm catalytic converters. Notice the Z and the P in the name. Most newer oils still contain zinc, but at a greatly reduced quantity. ZDDP also helps with piston ring wear. The whole point is if you reduce the phosphorus content to protect the converter, you also increase cam lobe and lifter wear. Personally, I'd rather replace a converter than a camshaft. Shell Rotella T6 Synthetic Diesel oil contains somewhere around 1200 ppm zinc whereas Valvoline Max Life only has around 600 ppm. I'm not sure of the actual figures, but those are close. The Rotella also is more stable at higher temperatures.

I know a guy at NAPA and he says they can't keep Rotella on the shelves for long. They are selling a ton of it. It's a bit pricey at $30/gal. but Amazon has a sale 'til the end of the month for $19.99 with a mail-in rebate that brings it down to $12.99, limit 2. I just bought 3 because you need 1 and 1/2 for an oil change. I've been using the 5W-40 for awhile. Advance Auto has it on sale every couple of months for $19.99.

00t444e

I use 15w40 diesel oil because of the zinc and other additives, it also give my better oil pressure. I'm not worried about what it does to the cat because I don't have one.

tech

The only reason they removedzinc is that it will coat the catalytic converter and it will stop working and because of that the EPA stopped letting them put it in most oils . Yes15w40 diesel oil does have some zinc in it but they did lower the amount that is in it , most newer motors have roller cams in them and don't need the zinc any more . They did put other additives in the oil to try to help to make up for no zinc , The only time you need to add zinc to your oil is when you are braking in a new motor or cam and lifters . I use Mobil 1 10w40 and I have about 165000 miles on my 2001 XJ .

dave1123

Molybdenum disulfide, or Moly-D as it's known, is a good substitute for zinc, but you have to add it to every oil change. Oils that have reduced zinc have some in them. It's black in color so some people don't like it. The old Isky Cam Lube was Moly-D and STP mixed.

BlueRidgeMark

Exactly. The change had nothing to do with what is good for the engine. It was 100% about emissions. (Same reason you are seeing recommendations for transmission service from 60k to 100k these days. It's not because it's actually a good thing.) The design is the same, and a flat tappet design lasts longer with zinc. Will you notice any immediate difference? No, but it will affect the longevity of your engine

MBredestege

Read this thread.
Very informative.
https://www.cherokeeforum.com/f2/rot...essing-188168/

RocketMouse

Hey... thanks for all the input everyone. I wanted this to be specific and not turn into an out of control "oil thread". The reason I asked this question was I have a buddy of mine that is a professional mechanic. Me I've always known how to work on the vehicle I own, but not the industry as a whole professionally.
And he mentioned that the later years 4.0s really didn't need the extra zinc/phosphorous, but he's not specifically a Jeep mechanic. He just said that using something like RP because of the way it keeps a film on parts even after being shut off does the trick quite well.

If there was truth to say my 99 not needing the zinc even though it's a flat tappet design, I don't want to do damage, I want to keep her going as long as possible. She only has 105k on the clock as of now. I've been running the 5w 40 T6 for over a year now because of the zinc. And like some have mentioned... I could give a rats a** about the cat. I too would rather replace a cat than a cam.

Also, is their any truth to zinc only being needed/required during the break-in period of the motor? Or is it good for our 4.0s for life just as some extra "insurance" against premature cam wear?

I also heard that the latest version of T6 they upped the zinc from around 1000 ppm to over 1200. Even saw the proof on another site where someone with our 4.0s did a blackstone test of previous version and new formula and posted the results data sheets to prove it.

I'm so glad this turned into a normal discussion and didn't go south faster than a snowball in hell.

RocketMouse

^^^ yeah.. I saw and was part of that one from the sidelines when it was active. There was some crap on the fringe...but the meat was pretty solid.

5-Speed

Just throwing out a fun fact about ZDDP that most people skip over, it doesnt start doing its thing until oil temps are over 170°ish. Now that may not seem like a lot but oil takes quite a bit longer to heat up then coolant. You may drive for 20 min and the oil still doesnt get up to a hot enough temp to get the ZDDP working. So if you are doing a bunch of short trips, having ZDDP in your oil does absolutely no good.

RocketMouse

Crap 5-Speed..... I live in a town the size of a postage stamp..so I generally don't take the Jeep very far..

So it's temperature dependent to activate and not just working because it's suspended in the oil? Well that sucks a bag of rocks. I want something that will leave a good film on the parts to protect at startup and protect our flat tappet lifter/cam setup.... that's why I was actually considering RP because of the cold start tests I've seen with that stuff vs. other full synthetics... they coated the bearings and other parts, then took the oil supply away...and I'll be darned if that film didn't keep those spinning parts as quiet as a mouse fart and with no damage at all afterwards.

I know my baby only has 105k on the clock...but I plan on having her around for a long time and want to do what's best for extending the lifespan of critical parts like motor and drive-train. I've been using T6 since I got her a year and a half ago for the zinc and detergent package.. she passed emissions in CO which are fairly strict...and uses absolutely zero oil and shifts smooth too.
I do have to replace failing u-joints this weekend...after the lift and at a different angle the OEMs that have been on for the past 20 years didn't like being several degrees steeper. But that's my own fault not the Jeep. lol

5-Speed

Its honestly really nothing to worry about. Your cam and lifters are already broken in so the need for a high ZDDP content really isnt there. Plus there is also this thing know as "flash temperature". Think of that as more of a hot spot in the oil. Example, when the lifter meets the cam, the oil between the lifter and cam gets compressed. Compression equals heat. So that compressed oil gets super hot, very quickly, helping the ZDDP do its thing in that one spot. But once that oil joins all the other oil in the pan, it cools back down to normal temp. Long story short, the parts that really need the ZDDP get hot enough to work before the oil hits its optimal temp but overall, the oil does not get hot enough to coat the entire engine. I would say its more important to get the oil hot enough to boil off all the water in the oil rather then to get the ZDDP working. Hope that made sense.

RocketMouse

Yeah that made sense. And the second half of my initial question was the fact that.... do we really need the extra zinc and phosphorous after a flat tappet lifter & cam setup is already broken in. I mean if it's some extra insurance for long lifespan then why not...but if it truly doesn't make any difference after the fact then I would think it would be better to use one that has a great film left on the parts for the next cold start...but I also know that the T6 does have a great detergent package for our 4.0s and seen the proof on oil analysis data sheets. And I honestly don't know/think that RP has a similar detergent package for cleaning and keeping it clean. Although their formula is frickin' awesome for the film left on parts for cold starts. When I saw the demonstration I was like "holy crap". The other full synthetics they did the same test on came to a screeching halt and the RP kept spinning quiet as could be with no damage and no other oil supply except the film on the parts.