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Hi Gary, your consumption sounds high, I'll calculate it as about 1/2Q per tank maybe 250 miles, = about 2Q per 1000 miles. I consider that oil consumption becomes an issue worth looking into at 1Q/1000 miles, so you are at double that threshold. Some early consumption may be reasonable but with modern machining it is not the norm, and by 5K you should be past any break-in expectation.
First thing is to verify no leakage. If there is external leakage, deal with that.
If no leakage, there is internal consumption. After 5K I doubt that it is going to go away. You may have a fair complaint against your machine shop/rebuilder, but if they have done it wrong the first time you may not want to let them try again. I have to suspect that they may be using older technology to machine the block, ie machining the cylinder bores to an incorrect finish for the chosen rings. I think you refer to chrome-moly rings which may not seat as readily as cast iron rings. Optimum finish for the cylinder bores may vary with the ring selection, the ring mfr would be the best authority there.
Basically there are two avenues for internal consumption, past the rings as above, or past the valve seals and guides. You need to clarify what work was done in the course of the rebuild. Was the block bored and finished? With new pistons, I would think so. Were the cylinder heads worked over with new valve guides and seals?
I am not a machinist so please take my comments as based on my general understanding. Nailing a specific cause of internal consumption is always problematical. If there is internal consumption, there is oil getting into the combustion chamber. Careful examination of the spark plugs may offer clues. I think I have seen it proposed that darkening of the porcelain around the center electrode on one side only suggests oil entering from a valve guide, while uniform darkening suggests oil from the rings.
No silver bullets here. Please report back. Job 1 would be to carefully track and record oil consumption.
I do not believe synthetic oil is an issue, contrary to popular rumor. It is superior to dinosaur oil for many reasons. Many manufacturers use it from the factory.
posted by 198.69.25...
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