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Forums are meant to help each other, don't be sorry as I am glad you posted here!

Please send photos or detailed descriptions of what you find, it is of great help to find out where the problem is... Were these 2.3L engines? I bet the majority of people who owned these cars while they were fresh just didn't change oil on time, hence the build up.

I will let you know if I can find anything on the piston ring spec.

Hey Big Dill, thanks for the feedback. I posted here yesterday but for some reason the post never appeared. Must have gone out to the nether...

I got the specs for the piston ring gap. Still wish I could find the 10,000 page pdf of the 2010 era Mazda 3. I have the Haynes book (actually bought it for the boy, but he's not interested yet) and I have the 3000 page pdf that I got for $14 bucks. Then I found the same one for free while looking for the 10,000 page one.
I need to figure out the picture posting method here, then I’ll start posting pics. I want to build a thread for the 2.0 rebuild, but this holiday week has been hectic.. can’t wait to go back to work so the local boss doesn’t find more for me to do.
I looked through some of the photos I took during the tear down and will take some more as I finish the old block inspection. Will also include some detailed photos of the intake. I’ll have to come back here and update a post with the link. But I’m thinking too far ahead now….
Also; no. These were both 2.0 engines.
 

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It's not a hi-jack when the OP is a one-and-done airhead, like the guy who started this thread.


^^ +1 ^^
My daughter's 2011 2.0L 3i has never used any oil whatsoever, with regular 7.5K OCIs, and an 11K extended oil change the last time. I've used only top-shelf 0W-20 full synthetic and Mazda filters, and regularly check the oil between changes.

I listened to it as she started it up at -1F this morning, and it sounded great. Nothing 'extra' from the engine, just a nice solid purring sound. I love that engine :wink2:


Thanks for the feedback m3iguy;



I’m glad to hear you’ve had good luck with 2011 2.0. The engine I got from the junk yard in PA is a 2011 2.0 w/ 111k miles on it. What kind of oil have you been using? I’m planning on using Castrol 0w-20 synth.



Which brings me to a question for all; since I’m new to the synthetic oil world, what should I start with when I run the engine through the brake in period? Do these Mazda’s come from the factory with synthetic oil and 0 miles on the engine? So you’re running synthetic for the first 5k miles?
Back to the “disappearing oil” issue:
As I was rambling in yesterday’s post, I was considering the PCV comment. I think this may be one of the key players in the overall issue. I’ll need to look at the design of the PCV and vacuum system and see if anything jumps out.


One of the other key players (IMHO) may be the fuel mixture. I’ll have to check the engine that threw a rod, but the one I got used from the junk yard was apparently running very rich. The cylinders looked like cylindrical mirrors. And the carbon build up was thick (in the areas where it would tend to not get blown off). I’ll need to check the VCU to make sure it has the appropriate code when we get it running again.


As I see it: (and I’m way open for suggestions and corrections here) the high mixture causes an excess in un-burnt fuel to deposit in the form of carbon. The carbon builds up (this happens relatively fast) to the point at which it flakes off during the combustion part of the cycle and gets stuck to the cylinder wall.

The piston comes up and collects the carbon which causes a build up along the perimeter of the piston (the compression ring). These larger particles do two things. 1: They get ground down and work their way throughout the ring grooves, eventually making their way to the oil ring and mixing with the oil (ever notice the black stuff that comes out when you change your oil? :smile2: It’s clear when it goes in…). And 2: Some of the larger particles get blown out of the combustion chamber; I believe causing pitting on the valve lands along the way. (I had to have my valves and valve lands cut because there were some really deep pits.)


Both of these processes will eventually lead to lose of compression. The lost compression into the crankcase (blow-by) will increase as the compression rings become restricted by the excess buildup of carbon between the ring and the piston ring groove surfaces. The buildup affects the combustion ring’s tendency to spring back as the piston travels back up the cylinder. The affect is that it takes longer due to increased friction. When this happens the ring can no longer apply adequate pressure to the cylinder wall.



Lost ring pressure on the cylinder wall means the rings will start to float a little as the piston travels up. When this happens, some carbon (very small particles) will roll between the cylinder wall and the surface of the ring. (That’s a very nice polishing method.) At the same time they are polishing the cylinder walls the rings are floating higher allowing larger carbon particles between the ring surface and the cylinder wall. Now we’re getting even more blow-by and lost compression.


It’s a vicious cycle that just keeps growing as the engine hours accumulate. Poor oil quality and a low quality oil filter (one that doesn’t filter to a low enough micron level) coupled with longer than recommended OCIs will contribute to more and more blow-by creating the perfect storm; literally.


Now the crankcase is pressurized. Not so much that it blows your dip stick out, but higher than the PCV system was designed to handle. Where does all that extra air go? Back to the intake (I think :nerd:). But, now that it’s traveling at a higher speed and volume; it’s taking more oil vapor along for the ride.
And so we’re back to the beginning of the story; which is a lot of air, mixed with too much fuel, combined with some dirty air, mixed with too much oil, and the process starts all over again. But it’s worse now.


Ok. Those are my thoughts for the day. I have to go pick up a used AC compressor for Old Blue and get back to the 2.0 waiting for me in the garage.
 

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... What kind of oil have you been using? I’m planning on using Castrol 0w-20 synth...
I use Pennzoil or Valvoline full synthetic, but also believe that any of the other competing, top-shelf full syn (such as Castrol) would be fine as well.

... what should I start with when I run the engine through the brake in period? ...
Are you rebuilding the boneyard engine? If not, there would be no break in period.

... As I see it: (and I’m way open for suggestions and corrections here) the high mixture causes an excess in un-burnt fuel to deposit in the form of carbon. ...
IMO, extended running rich would dilute the oil and trash the engine due to lack of lubrication. However, running overly rich would likely not be something that could continue for an extended period of time. Case in point: last Winter, my Chevy's MAP sensor started to go bad with no code set, and resulted in rich fuel trims around -20. That rich condition was something which was painfully obvious, and could not be ignored for even a brief period of time.

Now I suppose one could argue that running slightly rich might go undetected. Although that may be true, IMO poor oil maintenance is by far the most likely cause of your 2.0L issues. Best of luck getting it back on the road successfully!
 

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I have been using liquimoly 5W20 since I owned the car, I am nearing 250k miles now and compression is still close to original and no oil loss. I change it every 5k miles though.

I think your posts were getting blocked for the suspicious length of them, haha. I like details when its something interesting, but I have seen random advertisements that pop up on the forums.

Where I live, very few people mess around with the control units on these cars, im talking the NA cars, not the speeds. That being said, I have seen so many cars with this problem, and none of them have been messed with electronically. I personally believe it trails down to the maintenance history of the vehicle.

People who buy new econoboxes like the 3s don't necessarily buy a car to take care of it. They buy a new car for it to be trouble free. I believe the 2.3L engine is just plagued with some problem with PCV path.

The theory you have is pretty intricate, but I would have to disagree, you don't have to lose compression for oil to get consumed. I have heard the older proteges consume oil because the oil ring was stuck to the piston, but compression was still good!
Another point to that, my moms 2006 3 with the 2.3L drinks oil like like a pig, but compression is good... No smoke or leak either. might not be an issue with the rings either.

As I mentioned before, one big clue leading me to believe it is the PCV system is that my moms cars intake is covered in seemingly fresh oil, where as my cars intake is dry. I haven't checked if that oil was pooling up at the bottom of the intake, but maybe it gets burned in trace amounts under high air velocity in the intake.
 

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This thread interests me because I serviced the valve cover gasket, O2 sensors, and spark plugs last year on my 3. I had the transmission rebuilt a couple of weeks ago and the car runs strong with 14xK miles. It had 39K miles when I bought it about 7 years ago. I have noticed zero oil consumption issues with the engine, aside from having to replace the valve cover gasket, so perhaps that's why these cars have a bad rep for doing so. I use synthetic oil changed at 7,500 mile intervals.

I was wishing I'd known about the 2.5L swap *before* I had serviced the engine; however, I'm thinking I can get another 5 years out of this car.
 

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OK guys add me to the list of Oil hungry 2.3L owners.

I bought my car new almost exactly 16 years ago. I've done all the oil changes on the car myself. Back when I used to autocross and tow regularly I used Mobil1 (5w30 in the winter and 10w30 in the summer) and changed the oil every 3000 miles. When I stopped autocrossing and towing I bumped the OCI up to 5000 miles and when Exxon bought Mobil and switched Mobil1 to a semi-synthetic I switched to MaxLife (red bottle).

I have ~145K miles on the car now, obviously some things have broken (thermostat, a few fuel purge solenoid valves, alternator) but in general it's been very reliable.

Last time I changed the oil was about 6000 miles due to two ~1000 mile road trips but I was alarmed to only get about 1.75 quarts out. I admit I had not been regularly checking the oil because I've never once had to add oil between oil changes before.

In general though the car is still running great and just passed it's smog test a couple weeks ago.

Checked it last weekend, about 500 miles since the last oil change and it was a quart low.

So needless to say this is all very concerning to me. I'm due for new spark plugs so I will check the old plugs for signs of oil and go from there.
 
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