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I've just picked my car up from mapping and it's now burning more oil than ever. It's always burnt a little oil but today I drove 100 miles and it's burnt the length of the "F" on the dipstick ( I keep it filled to the top of the "F" ) I know that's not much but that's a lot for 100 miles. Although they were "spirited" and I hit the limiter a few times

Please help me figure out why I've completely had enough of this car *money pit

Here's the facts

The car has a fresh head on it with all new valve seals. Under 1000 miles ago.
The compression is 200 on 3 of them and 220 on 1? No.2
The car puffs blue smoke after you rev it.
It seems to burn more oil when it hits the limiter. ( has launch control so limiter can be 4500 )
10/40 oil semi synth
If I do a compression test on a cylinder and leave it at 200 psi the pressure doesn't drop at all. I can take the cap off the cam cover or remove the dipstick and can here no hissing or loss of pressure.
It's done 120,000 miles
New pcv valve

Please help me figure this out or I think it's finally time to get rid.
 

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Because the compression is great, it doesn't mean the oil rings are. :( . Because it is smoking consistently, it would appear to be the oil rings. Depending upon how high mileage the engine is, the bores could have worn oval, which would prevent the oil rings from functioning as they should. Or they might have become clogged in their grooves. You could try running some Redex (do they still sell that?), through the engine, or one of the better proprietary oil treatments on the market.
Edit to add: if it IS just the oil rings, as it sounds to me, a leakdown test wouldn't neccessarily show anything, because the compression ring(s) seem to be doing their job properly (good compression results). Oil rings condition will only affect compression readings if the top compression rings have worn badly.
 

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Well if I can find out that it's definitely not the head I at least know that's it's the bottom end so I can get looking for a low milage one then swap it out.

Tbh I just need to know if it's defiantly the head or bottom end so I cam decide what to do. I am definitely not paying for another head rebuild though.
 

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Before you despair, consider this. If you're filling to the top of the "F", you're overfilling it, it should max at the line below it, and the recommended level is anywhere between the two lines. If you overfill it, as the pistons are splash lubricated, you'll use oil faster due to excessive oil being thrown up by the reciprocating bits, and finding its way past the oil rings, especially when you're driving it hard. Too much oil will just quickly burn off, causing smoke, carbon in the combustion areas, and will eventually cock up the cat and sensors (if you have any). As the level drops the usage will slow down.

The oil level should be anywhere between the low and high marks, but definitely not above the top line. Try dropping the level a bit and then see how much it uses. And, although Mazdas tend not to use much oil. IIRC correctly from my Mazda dealer days, something like 500 miles to the pint is considered acceptable by Mazda, and the older the engine the more it'll use.

Bernard
 

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Discussion Starter · #8 ·
Thanks for the reply.

I'll keep it below the line for the next week or so and see if it improves but I have kept it at the top of the "F" for a couple of years now and it's only just started burning oil quicker and noticeably smoking more.
 

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If it overheated originally it could be that the piston rings have lost their tension .Common problem after overheating especially on jap engines ie Micra etc. This is why some garages will not do head overhaul after overheating .I have been working on jap cars for nearly 25 years now and this happens regular. Not so much on other brands for some reason .Some people rather fit good used engine rather than repairing original
 

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Discussion Starter · #10 ·
Just did a leakdown test and it's 4% loss on all 4 cylinders so the head is fine. I guess all it can be now is the oil rings.

The engine builders said that they don't think it's an alarming amount of smoke and to just leave it as it seems to only burn oil when pushed hard.

I'm gonna drive it sensibly to and from work for a week and see if burns any and go from there. If it does then I guess I'm changing the bottom end for the lowest mileage one I can find or rebuilding the spare one I have in the garage with new rings.
 
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