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Here are some things that I have done to have a 190K+ mileage V6 engine. I have not babied my engine at all except the first few thousand miles since new and do drive quite aggressively. After reading so many horror stories, I decided to give some advice to all those that have this engine.

1. If new (probably does not apply any more), vary engine RPM for the first 500 or so miles. This will help break the engine in.

2. I have used Mazda filters and went to Mazda dealerships for oil changes for first 15K miles oil (free oil changes came with the car). After that, I have been using Pureone oil filters with either Amsoil 5W20 or Mobil 1 5W20 fully synthetic every 5K miles.

3. Replace my PCV valve every 20K or every year. They are not that expensive. I also replaced the PCV hose at around 150K. It is a revised design. I seems thicker and sturdier compared to the old one. I noticed that the old one would get compressed as if someone were squeezing it at idle (highest engine vacuum). Don't know if this leads to oil being sucked into the engine as well since the hose has a smaller opening now causing increased pressure in the hose.

4. Check your oil regularly (every few days, week, or gas fill up). Also check it on a level surface. Your readings will vary if you're on a hill or sloped street.

5. Get those flashing check engine lights taken care of quickly. That usually means you have an engine misfire. This will cause unburnt gas to enter the cats and cause the internals to melt, then eventually breaking down and getting sucked into your engine. I did get the misfire CEL at around 105K and did not drive it at all. Had it towed to the dealership where they raped me for changing all the spark plugs and coils. I was gonna do it myself, but too cold out.

6. If you get the precat check engine light, you need to replace the cats ASAP! Try not to drive the vehicle. Either replace with OEM cats or MSDS or CPE headers. I currently have MSDS headers with a high flow cat using stock cat back and have had them since 123K miles. I believe there is a federal warranty that requires the dealership to replace them even after the standard warranty is overdue.

7. Fix any oil leaks (oil pan gasket, front crankshaft seal, rear main seal)

8. Replace your spark plugs and coils. I replace my spark plugs with stock ones every 60K miles. I currently have NGk iridiums though.

9. For those with the top end ticking noise, I have had that since day 1.

10. I have used Techron , Seafoam and BG 44k fuel additives once in a blue moon.

11. I always if possible fill up at a major chain gas station....except BP
(don't ask)

12. I always warm up my engine when starting from cold. I wait at least until the temp gauge starts moving and/ or around 1K rpms. Some others wait a bit longer. I keep the rpms below 2K while driving till the engine warms up fully.

My current oil consumption is 1-1.5 quarts every 5K miles. If I missed something, please add on.
 

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Thanks for the info.

My 6 is the first car I've owned from the era of multiple/close-coupled catalytic converters. It looks like keeping unlit fuel and oil out of the cat baffling is critical.
 

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Thanks Chilimax for the tips. I just changed my PCV (without removing the manifold) and also replaced the hose. I paid $1 and bought 5/8" vacuum hose from Checker and cut to fit. I know some people have had problems with the hose collapsing, so I am going to keep an eye on the hose to see how it holds up. I did put a clamp around the middle of the hose for a little extra support. I paid $10 for the PCV shipped from Rock Auto. I last changed the PCV 30,000 miles ago, and noticed the older PCV didn't rattle near as much as the new one when shook, so I could tell it was slowly getting sludged up. I think alot of people change the spark plugs but ignore the coils, and the coils seem to be a real weak point. I think it's key to replace all of the coils if somebody wants to hit high mileage on their 6. They will eventually all go bad, and you may drive around for awhile with a coil not working at 100%, but not get a CEL from it and not notice the slight misfire. This will eventually destroy the precats, so don't risk it and just replace all of the coils. I paid around $200 for 6 Standard Motor Products coils from Rock Auto, and have had them installed for around 20,000 miles with 0 issues. I just passed 106,000 miles and still going strong with original clutch and pre-cats. I change my oil every 3k on the dot (overkill I know), and check my oil levels probably 2 or 3 times a week. My 6 doesn't burn a lick of oil, but I do have a slow but steady leak at the front of the engine (don't know if it's the timing cover, cam seal, or what?).
 

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check your axle boot on the passenger side, closest to your motor, your clamp may be losing tension, like mine and slinging grease on your motor. i degreased my motor and found out this problem.

i would add upstream O2 sensors to that list above as preventive maintenance, to protect the precats too!
 

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I will double check the axle boot clamp, but it's quite a bit of sludge on the engine, so I don't know if there is enough grease in the boot to cause it or not? But I will take a look and see. It is weird though because I have noticed this for awhile, and don't ever see my oil levels drop at all. Thanks for the tip I will check and see.
 

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there's no reason to remove the manifold on the v6 to remove the PCV valve. you only have to do that on the 2.3 because the PCV is located behind the intake manifold. ;)
you dont have to remove the intake, true on the V6, but if you have BIG hands, its a tight squeeze with the needle nose pliers in hand to twist the PCV out.
 

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Replacing coils for the sake of replacing is silly.

so are alot of the other ideas here.

I just replaced my first PCV at 125k, and still have 3-6 OEM coils from 7 YEARS ago. I removed the cats at 119k and they were still brand spankin new inside.

no discussion of the reliability of the ATX or Plenum gaskets which if anything is the most fail prone things you will have to deal with.....

I'm also amazed at what people pay for parts and then on top of that pay to have them installed. Yall need to start shopping around a bit.
 

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Because you haven't had problems with the coils doesn't mean that logic applies across the board to every Mazda 6. I am just saying that if you want to be proactive rather than reactive, and increase the probability of the Mazda 6 reaching 200,000 miles +, it's better to error on the safe side and eliminate some of the 6 "killers". And seeing that many people have had issues with the coils, that only points to a higher probability of experiencing issues. I don't mind spending a little extra $ as I go along to help reduce my chance of ruining the engine, and being stuck with a loan on a car that isn't worth squat. Just my preference and what level of risk I am willing to take on.
 

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there's no reason to remove the manifold on the v6 to remove the PCV valve. you only have to do that on the 2.3 because the PCV is located behind the intake manifold. ;)
It's not necessary, and that's why I didn't remove the manifold. But like Edward pointed out, if you have bigger hands, it is a bit*h to fit your hands in such a small space to be able to remove the PCV. I read on here somewhere that you can just grab the PCV hose and twist until it loosens the PCV valve, however I tried that and couldn't get enough traction and torque to break it loose. I had to squeeze my hand in close enough to get plyers on the valve and break it loose, which jacked up my hands. It definitely can be done, but can be a pain because of the limited space.
 

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Because you haven't had problems with the coils doesn't mean that logic applies across the board to every Mazda 6. I am just saying that if you want to be proactive rather than reactive, and increase the probability of the Mazda 6 reaching 200,000 miles +, it's better to error on the safe side and eliminate some of the 6 "killers". And seeing that many people have had issues with the coils, that only points to a higher probability of experiencing issues. I don't mind spending a little extra $ as I go along to help reduce my chance of ruining the engine, and being stuck with a loan on a car that isn't worth squat. Just my preference and what level of risk I am willing to take on.
noone has linked Coils to engine failure short of prolonged exposure to raw fuel in the exhaust....... which can still be eliminated with a removal of the cats. Without the cats, you would have a small little burp of unburnt fuel as you drove down the block and nothing more.

COPs are very common things and have been used for years on cars without issue. They are designed to fail and still keep you on the road.... instead of stranded like a dead Dizzy. Replacing them does not eliminate the probablity they will fail..... nor does dumping money into fixing something that isn't broken.

I guess it is your money and you can spend it how you like.

Most of this is fear mongering at best without really any empirical evidence.
 

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If I had headers, or gutted pre-cats, you are right in the fact that I would not be nearly as worried about the coils, in fact I would only replace one if it went bad. But I am being proactive because I have stock exhaust and dread the pre-cat failure. It is absolutely based on a level of fear. I don't mean to suggest that replacing the coils eliminates the risk, because any coil can fail at any time. I am trying to play the numbers game and am attempting to "reduce" my risk, not eliminate it as that isn't possible unless I rode a bicycle. And you are right again in the fact that I don't have any real evidence to suggest that failing coils are the sole cause of pre-cat failure, but my own opinion is that they are one of the possible contributing factors. I am trying to be proactive on maintaining what I feel to be the contributing factors (spark plugs, pcv, coils, etc.) in order to reduce my risk. Maybe I am right and maybe I am wrong, who knows? But I am willing to spend a few hundred extra dollars in present time in order to hopefully extend the life of my car. There are no gaurantees that it will extend the life of my car, but hopefully I can improve my odds. I am at 106,000 miles and running solid, so I will stick with my plan and time will tell if it was the right move or not. To each their own.
 

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there have been plenty people on here with multiple misfires then damaged precats due to a failed coil /coils. so far, i've only had 1 coil to start dying slowly(hesitating/bucking under a load). after reading several cases here about misfires then precat+engine death, i parked my car and bought a new coil quick! if the headers wasn't a pain to install and/or i could get them for a better price, i would've had a pair by now! im cheap and im married so you already know lol.
 

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Assuming each coil has an average lifespan of x miles, we know that some will last longer, and some will not. In any case, periodically replacing all 6 at one time will increase coil reliability. That is a simple mathematical fact. That means the odds of you getting stranded because of a failed COP is less.

Is doing this necessary to make your car last longer? I'm not really sure, although I am a huge proponent of preventive maintenance. As was said, it's all about how you want to spend your money. You can change them once every year, or once every 10 years.

Then again, as flipper said, more data is needed on that matter.
 

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It's not necessary, and that's why I didn't remove the manifold. But like Edward pointed out, if you have bigger hands, it is a bit*h to fit your hands in such a small space to be able to remove the PCV. I read on here somewhere that you can just grab the PCV hose and twist until it loosens the PCV valve, however I tried that and couldn't get enough traction and torque to break it loose. I had to squeeze my hand in close enough to get plyers on the valve and break it loose, which jacked up my hands. It definitely can be done, but can be a pain because of the limited space.
All you need is a wrench. The valve has a square flange on it for just that purpose. I don't recall what size it was, but it's something like an 18mm. You should be able to determine the size using the new one. It's a piece of cake to change.
 

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there is no code for Pre-cat failure.

if a "O2 sensor with no reading" or w/e the code is comes up........ you are already up shit creek.

CATs are warrantied federally for 80k or 8 years
I did get the P0421 CEL which could be the cats, exhaust leak, bad O2 sensor or bad PCM. I could've had a bad O2, but replaced both.
 

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All you need is a wrench. The valve has a square flange on it for just that purpose. I don't recall what size it was, but it's something like an 18mm. You should be able to determine the size using the new one. It's a piece of cake to change.
The aftermarket PCV valve I already had on the car had the square flange, but there is also some sort of metal "pipe" wrapped around it that interferes with the flange and doesn't allow you to get a wrench on it. I have no idea what the metal pipe is for, but I think it's useless. That is what made it so difficult for me is I could not get a wrench on it at all.
 

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Is there a posting somewhere that gives the specs on testing the output of the COP?
 
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