Originally Posted By: Artem
When I first pulled the valve cover (prior to using Amsoil) the top end was already dirty, so I say Mobil 1 and 3-5k OCIs did it with the help of the poor natural design of this engine.
I'm sure it would have happened with any oil though.
Much like the 1ZZ issue, no, oil choice would have had no effect. Even 1k OCIs with PU wouldn't have prevented it.
I'm familiar with the soft, sticky, gooey buildup you're dealing with, from a neglected post-RENIX Jeep 4.0 I dealt with some 12 years ago. I knew at the onset of this discussion that you wouldn't see results but I bit my tongue, hoping to be proven wrong because this buildup is not fun to deal with and a product that could handle it would be a godsend.
The buildup you are dealing with is the result of the oil flashing off on hotspots, and that includes any cleaning additive, which would flash off before it could do any cleaning, adding to the buildup instead. What you're dealing with is a blend of coke (carbon), varnish, and any additives present in the oil, thus why it's black/brown, sticky, yet still a little slick. The only fix here is a straight solvent, carb cleaner or brake parts cleaner. Once you've got it cleaned up and drain the sump, you'll want to rinse the top end and flood the sump with 0w20 or a blend of MMO and a cheap 5w30, to flush out any residual bits of this [censored] so it doesn't redeposit elsewhere (it will emulsify and find its way THROUGH your oil filter), then drain the sump again and fill with whatever synthetic 5w30 you can get for cheap, which you'll want to dump after 1-1.5k.
From there, maintain with MMO at for the last 500-1000 miles of each OCI, or (dare I say) maintenance doses of ARX might fit the bill as it should increase the flashpoint of the oil (MMO will lower it), which should prevent the buildup in the first place. Heck, if my canola experiment pans out, 8oz of that in the sump will increase the flashpoint of any commercially available PCMO or HDEO, which would also prevent this buildup.
Running 1:2 antifreeze:water (1/3 antifreeze) in your cooling system, rather than 1:1, will increase the cooling capacity, as well, which will reduce the hotspots to some degree. If you do this, err on the side of a little more antifreeze, as the boiling point of the mix is affected and if you get too far below 33% you'll boil your coolant off.
