Fortunately, I have an AP2 that shows no noticeable amount of oil consumption over an entire OCI (usually 5K miles). But over the years here on S2KI, I've always wondered what the root cause is for AP1's reporting such high oil consumption rates. I read this thread over on BITOG this morning and it helped me understand a little more about what causes high oil consumption. It's a long read and gets pretty scientific/technical in some areas, but if you are involved with an oil consumer, it's worth the read:

http://www.bobistheoilguy.com/forums/ubbth...659#Post1371659

Also, if you are concerned enough about your consumption rate, I believe this product can help considerably with the problem (it's worth a try before buying a new cylinder head):

http://auto-rx.com/

 

#1 - Brake-in procedure & not using the oil that came with the new car for the time Honda thinks it should be used.
IMO that covers 75% of it.
The FRM cylinder walls need to be broken-in right.
Using syn oils too soon stops brake-in IMO.
#2 - Cylinder honing technique - IIRC Honda changed it by using a dummy head installed on the block.

But.. adding the Krank-vents reduced oil comsuption on my (first) engine, that does suggest piston ring pressure is a factor.
My MY05 engine (still the 2.0) uses almost no oil.

That paper is pretty interesting though
I don't think you could look at the F20/F22 and think: this is a low load & low rpm marine engine

 

Does your new F20 engine have a dummy head installed Spitfire?

I agree that the engines being researched didn't fit the F20 profile, but I think the principles being discussed are probably universal for internal combustion engines. The perfect storm of heat, byproducts, oil viscosity, base oils, load (Honda wants us to use a light load for break-in), and cylinder head design will create cumulative laquering and coking, causing increased blow-by, loss of compression and oil consumption. Am I getting close on this?

It may be anecdotal, but i think the poor design of the AP1 F20C cylinder heads is a unusually productive factory for deposit buildup on the FRM liners and coking of the rings. I think the blend of concentrated Lanolins and polyoil esters in Auto-Rx is the ticket for those experiencing compression loss and high oil consumption.

Here's another article I like that shows how quickly deposits can bulid up in the engine using various base oil grades (it's a slide show so it's easy to read):

http://www.uniqema.com/irj/go/km/docs/docu...uct%20codes.pdf

 

During honing you mean?
I guess so, going by what I've been reading over the years about Honda changing the way they hone the F20 blocks.
The F22's have the same bore so that shouldn't matter.
Not even close IMO
Yeah, as long as the conditions are there, for a prolonged period of time as mentioned in the study.
IMO one can not compare a light loaded F20/F22 in rpm range from 800-5500 with any marine diesel engine with a general max rev of 900 rpm.
Where in the study comes cylinder head desing into play?

If the flat combustion chamber is what you mean, I think the F20/F22's don't have it.
Its a dome.

How did you reach that conclusion?

The slide show is interesting too.
Nice find

 

I really don't have any problem with any of your responses Spitfire. I like them. I thought when I first read this thesis it offered some generalities that might provide insight to some of the consumption/compression issues we see routinely with AP1 owners. If you think it's totally apples and oranges, then I'll delete the thread. No problem here...

 

Delete?
Who's talking about deleting anything?
No no no.
Don't delete.

Discuss.

 

Dummy head is called a torque plate. It simulates real-world torsional load during sleeving, honing, etc.

 

I cant speak for others but I think the f20 burns more oil than the f22. before I did my motor swap my old f20 would go through maybe 2-3qts between oil changes. but when I swapped to the f22 I noticed i didnt have to top it off. To this day I havent had to top off the oil.