Originally Posted By: dnewton3
I have to ask the OP ...
What is the goal you're trying to achieve here?
Are you trying to stop the lifter/piston noise? If so, is the noise prevalent at all times, only at start up, for a short duration after start up, or what???
What makes you think that a thicker engine oil will succeed where the Lucas didn't? I am not a big fan of additives generally, with only a few niche exceptions, and this isn't one of them. Here, the use of Lucas making your oil into a near-syrup product didn't solve whatever issue you're trying to avoid, and so your quest now is to make an already-thickened-lube even thicker by using 15w-40 with the Lucas?
1) Ditch the Lucas
2) pick any decent API lube you want to use; I highly suspect it's not going to make much difference overall.
I don't follow the Vortec 6.0L engine much, but they are legandary in terms of power-producing motors when modded. Just because it makes noise (presumably in stock form) does not mean it's on death's door. You mention that the noise is a known factor for that engine series, but does that mean it's about to die? I ask because I'm not imminently familiar with that engine. IOW - when they make noise, it is a signal for impending failure, or just an annoyance? Certain engine families have known noises that can be a signal for failure, or just a bother. Slapping timing chains are generally a bad deal. Etc ...
You ask if there is any benefit or detriment to using the HDEO. Not really in either manner. Any HDEO that is spark-rated is going to be fine to use. Generally an HDEO will have a bit better HTHS and/or higher TBN and cleaning agents, due to the concern for the diesel engine process. But those "benefits" don't necessarily translate into an assurance of "more" or "better" success in terms of a gasser. Unless you plan on greatly extending your OCIs, a higher TBN or greater detergent package isn't likely to gain you much. So while not harmful, I doubt it would be tangibly helpful, either. An example would be the HTHS effect. Say for example you use 10w-40, and the engine noise goes away right after an OCI, but then returns after 3k miles after lube shearing, then you would have three choices:
a) endure it and finish the OCI plan
b) OCI more often
c) pick a lube with greater HTHS factor, so that the shearing does not happen as soon
In this example, perhaps an HDEO with higher HTHS might make it to 5k miles, where the 10w-40 was thinning out sooner. So here, a 15w-40 HDEO might warrant the experiment. However, if the noise is present at all times, regardless of OCI factor or grade factor, then the HDEO is likely to do nothing to alter the problem. And let's not forget you already use the Lucas, so it's pretty darn thick already! How much "thicker" do you think the oil needs to be? And, is it possible that the oil is too thick? Perhaps the vis is actually limiting the lube from properly flowing into the lifters and the desired rate? I don't know this to be true, but it's not more unlikely than any other guess. For that matter, have you tried THINNING the lube; try using a 5w-30? Does the noise get "better" one way or the other? Don't judge it yourself; get a panel of friends to help you. What you hear may not be what others hear.
There is nothing wrong with trying something; go for it! But first establish a known baseline (UOAs, etc) and then when you change a variable, you can track if it truly made a difference as opposed to "feeling" your way through this. Admittedly, noises don't show up on a UOA report; we know that. But you get the point, I hope. If you're going to change, don't just do it for the sake of change. Do it with some manner of trying to establish a goal/direction, and then find a measurement method that helps discern any positive shift if present.
As a side note, if it's piston slap you're hearing, then no lube is going to greatly affect that. There are some engines that have forged Al pistons, and I have no idea of your engine is one of them. But if it is, know that the thermal expansion rate of the piston relative to the cast iron of the block is different, and piston slap is a not uncommon (and completely harmless) effect and will go away as the engine warms up. I had two first-gen Tundra 4.7L trucks many years ago. The first engine never made any noise; quiet as a mouse. The second truck had terrible piston slap until about 5 minutes of warm up, then it quieted down. Two nearly identical trucks with same engine series; two different results. No amount of oil tampering made the ticking go away; it just had to warm up and stabilize the metallurgy of the components and everything was fine.
IF this is the condition you're experiencing, you're chasing your tail.
My long-winded point is this:
a lube change may or may not have the effect you seek, but it's likely not harmful to try. Just don't get disappointed if it does not happen; it's a gamble.
As for your other questions (diffs and tranny fluids) ...
*Diff - presume you'll have the infamous G-80 gov-locker rear. Just use any GL-5 fluid that has a L/S friction modifier in it. Despite the significantly present ignorance that it's a "locker", it is in fact actually a clutch-driven limited slip unit that operates as a L/S, with the added feature of creating a greater clamping effect on the clutch pack when excessive slippage is present. Hence, it has clutches EXACTLY like any typical L/S unit. It needs FM to avoid chatter and nusance locking events.
*Tranny - 4L80E is a good tranny that just needs basic Dex/Merc type fluids. Any dino or syn that's targeted to this type application will work. Dexron III and Mercon are no longer licensed products, but the aftermarket makes good alternatives in many forms. If you want a long service life from the fluid, I'd recommend any syn version. (I like the Maxlife ATF from Valvoline, but by no means are you limited to this choice).
*X-fer case? You didn't mention, but if 4x4, then use a good syn ATF in the t-case. Easy to drain/fill with the plugs. The syn ATF will resist the effect of heat evaporation known to affect these units at times. Using a conventional ATF is fine, but you'll have to check fluid levels more often. As these units often become a "fill and forget" service factor, the syn gives a safety margin for those who are not as diligent about fluid maintenance as they should be.
Thank you for the detailed response. The noise is more of a nuisance at this point not a sign of imitate detonation. If was a sign of imitate death then its been on deaths doorstep since 80,000 and im at 189,000 LOL
. So i think on my next oil change ill the the DELO a shot. As fro the rear diff ive seem some say you need to add a LS additive and some say you don't....
