I have a 2000 mazda protege es with a stick shift and A/C. It is stock and it has 225,000 miles on it. It has always gotten over 30mpg and it varied depending on how much weight was in the car. It still is getting over 30mpg even with the problems i am having. The smoke has always been blue and it started eating more oil the more it smoked. I notice around 180,000 it would blow smoke when ever i had to get on the gas when i got on the freeway but that was the only time and it was very short. From 180,000 to 200,000 miles the check engine light would come one when i would get on the gas and then turn back off after a few hours. At 205,000 miles the check engine light turned on and would not turn off and my gas milage went down to about 26-28mpg and it would idle rough and it would barely idle with the a/c on. A OBD scanner said it was the cat or o2 sensors. I bought new o2 sensors and a new cat when i replaced them i notice the cat was clean and looked new and the o2 sensors were coated in ash. I replaced everything and and the light turned off and it ran great but it still would blow smoke when i got on the gas and the smoke was getting thicker and lasted a few more seconds. After about 210,000 the check engine light came on and it started running rough again this time i just replaced the top o2 sensor which was covered in ash and it ran great. At 215,00 it started blowing smoke when i would first start it up but only if the temp was below about 50 degrees or so. I live in utah and it only blew smoke during the winter. I also notice because i do a lot of freeway driving that it would eat a lot more oil if i drove it above 75mph than it would at 65mph. Im at 225,000 and the smoking is getting really bad on cold mornings and i am burning threw a quart of oil every 200 miles and the 02 sensors and spark plugs keep getting coated with ash but it seems to stop after it warms up and i am still getting 32mpg right now. I just want to know how to tell if its the piston rings or the valve stem seals or the valve gides? Everything is stock and original even the clutch and i have put almost no money into this car and i would like to keep it that way and see how long it will run. Any help would be great if there are links you can send me or if you have had the same problem and had it fixed i would like to know. I have always worked on my own cars. This car i havent worked on because it always runs but i dont want to rebuilt the whole motor is half of it is still in good working order. Thanks Bryan

 

A wet/dry compression test should tell the story. Remove all the spark plugs, disable spark and run a dry compression test. Record those numbers. Now add about a tablespoon of oil to a cylinder and run the compression test on each cylinder that way. If the compression comes up a lot it is likely carbon accumulation in the ring grooves causing them to stick into the ring grooves. If it were me i would load the cylinders up with Seafoam and let it sit a few hours to break up the carbon, add a bottle of engine restore to the crankcase, add a bottle of Techron to the gas tank ( Decarbons engines as you drive) and give it a week or so then change the oil. Valve seals generally cause smoke after idling a minute or two then taking off from a stop. Rings generally cause smoke on accel. It has a lot of miles on it so this procedure could save you 3k or so.

 

I had about a carbon copy of your description.see excessive crankcase pressure.After I fixed the head it still smoked.I pulled the head,pan and pistons and the oil rings were carboned up and stuck in the grooves.It took a long time to scrape all the carbon out of the ring grooves.I replaced only rod brgs and honed the cylinders and put back std.Knock on wood its running great.Got all parts from rock auto and was worth it if you do it yourself.

 

Excellent, thanks for the feedback!