Fresh engine- what oil?
- Thread starter Bonnewagon
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I use that for my home popped popcorn. YUM! Here is a great site that breaks down just about every oil. https://pqia.org/passenger-car-motor-oil/ There is more zinc than you think in today's oils and they still make the current SN rating. Just scroll down for your brand. And look at this chart. http://www.pqiamerica.com/apiserviceclass.htm
Maybe a mechanical cleaning could be done to the cats. They'll be lighter, flow alittle better, no issue with any level of zinc.Well, the easiest solution to not mess up the cats is don't hook them up. Run a straight pipe for the first thousand miles!
I'm late to the party. Personally, I think you're probably overthinking this.
As others have stated, cats were around lonnnng before zinc was reduced. Plus, you're dealing with a 55 year old engine design that had sloppy tolerances on a good day. Your biggest concern for break-in is the lesser quality materials used in today's replacement flat tappet cam and lifters.
If it were mine, I'd run Shell Rottella T with a bottle of additive. I'd probably repeat @3000 mile intervals. This was on the advice of my engine builder who used to include a copy of Comp Cams' break-in bulletin with each engine. Comp spec'd Rotella T.
As a side note, the last shop I worked for was a Jeep specialist. We used Valvoline conventional in our standard oil changes, which included probably a dozen 4.0 Jeeps per week -- mostly long term repeat customers. Never once did we have a cam/lifter failure. But those were all long-since broken in. 4.0 is pretty forgiving, you just need to get through break-in. Worry about the cats later, if you really feel you need to worry about something.
As others have stated, cats were around lonnnng before zinc was reduced. Plus, you're dealing with a 55 year old engine design that had sloppy tolerances on a good day. Your biggest concern for break-in is the lesser quality materials used in today's replacement flat tappet cam and lifters.
If it were mine, I'd run Shell Rottella T with a bottle of additive. I'd probably repeat @3000 mile intervals. This was on the advice of my engine builder who used to include a copy of Comp Cams' break-in bulletin with each engine. Comp spec'd Rotella T.
As a side note, the last shop I worked for was a Jeep specialist. We used Valvoline conventional in our standard oil changes, which included probably a dozen 4.0 Jeeps per week -- mostly long term repeat customers. Never once did we have a cam/lifter failure. But those were all long-since broken in. 4.0 is pretty forgiving, you just need to get through break-in. Worry about the cats later, if you really feel you need to worry about something.
You may be right. I am torn between ruining the cam on break-in vs ruining the Cats later. The engine had a steady diet of regularly available oil for 19 years already. It ran smooth as a sewing machine even with only 8 lbs oil pressure at the end. I am replacing the O2 sensores just because they are so hard to get at. The Cats are100k originals. The new cam is a Melling, lifters are Elgin, pushrods are Sealed Power. My guy doesn't go cheapola. I guess I am most confused by advice to use a dedicated break-in oil that is designed to allow a lot of wear so parts seat faster. Vs using the same oil you will use long term but change it often and maybe add ZDDP.
Well, at 19 years old and 100k, they'll either survive or they won't. Excessive oil consumption kills cats. Steady diet of coolant from seepy head gaskets kills cats. Driving around on a dead cylinder kills cats. And sometimes they just die of old age. In fact, you can have a pretty tired cat and never know it as long as the engine is in a reasonable state of health.
I'd still be more concerned with cam break-in.
I only gave my experience as what I'd do based on what my guy told me but YMMV. Probably best to ask your builder exactly what he recommends and follow it to a T. Save your oil/additive/filter receipts in case there's ever a reason that it comes into question.
I'd still be more concerned with cam break-in.
I only gave my experience as what I'd do based on what my guy told me but YMMV. Probably best to ask your builder exactly what he recommends and follow it to a T. Save your oil/additive/filter receipts in case there's ever a reason that it comes into question.
You have received good advice from many people. ZDDP is critical for initial flat tappet cam break in. Follow Comp Cams instructions for initial start and break in. I run initial oil for 4 heat cycles (heat up to normal temp, cool to ambient, repeat 3 more times). Drain oil and refill with same oil for 500 miles. Drain and go to the oil you plan on using long term, Multi Vis or Multi Vis Synthetic. These 4.0 AMC engines run usually around 300K before problems. High ZDDP will not hurt cats in 1000 miles. Quit second guessing yourself. Do what you think is right. There is no secret formula.
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