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Discussion Starter · #1 ·
I just purchased a mazda6 2004 v6 with 105k miles and I'm looking to find out what I should immediately maintenance as I have no idea what the maintenance history is on the vehicle. I have noticed my Mpg is very bad at the moment and I'm getting close to 12 mpg with about 50% city 50% highway driving and I'd like to determine the cause of this. I am thinking I likely need to replace spark plugs and engine air filter. I also noticed that when I am at lights or idling I smell some oil burning smell in the cabin and when I exit the car after a drive I can sometimes smell either burning oil or unburnt fuel. I was hoping I could get some info on what may need replacement and other things that are just generally good to replace at this mileage, thanks!
 

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2005 6s wagon 5MT
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171 Posts
Congrats on the purchase!

Good idea on the plugs and air filter. I'd also replace all 6 engine coils as well. They are well-known to go bad all the time on these cars.

The Duratec loves to leak oil. Common areas are valve cover gaskets and oil pan like a lot of engines, but the most annoying one is the timing cover gasket. I'd wager that's where your burning oil smell is coming from, as the cat runs right underneath. Replacing the gasket is a big job, basically everything has to come off the engine. It's almost not worth it unless the leak is really bad.

Keep a sharp eye out for any catalytic converter codes.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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4,542 Posts
@Alexnelson congrats and welcome to the group as well!
What @Ignatius Reilly said is spot on. The 2004 (and 2005) have the downstream catalytic converter from the front bank, running running down the right side (front) of the motor. This position means the leaking timing cover will drip right on it. Since the cabin fresh pull from that front corner, below the windscreen, you get to suck oil fumes when it does. Replacing that gasket is 10-12 hrs of work (timing job part 1 of 3 on youtube) and it generally lasts for about 6 months before leaking again.
Below is what another user (@98se5speed i believe) came up with as a solution.
Automotive tire Hood Automotive lighting Motor vehicle Grille


The things I would do immediately are as follows:
  • All 6 ignition coils
  • All 6 spark plugs
  • PCV Valve (upgrade to later hose and valve if possible)
  • Replace throttle body and upper intake gaskets.
  • Drain and refill automatic transmission fluid. (If never done (drain and refill 3x)
Other issues that may be present:
  • Clean all battery and engine/chassis grounds.
  • Front suspension bushings (click/clunk over bumps)
  • Lower motor mount (dog-bone)
  • Headlight covers (cleaning)
  • Headliner (re-glue)
  • Replace both upstream O2 sensors. (NTK with 100K mile lifespan)
This is what I have come up with over my time with the machine. Other will differ of course but I really would not hesitate on the ignition components.

Your OEM numbers for some of those things are as follows.
DENSO 673 6005 - Ignition Coils x6
Mazda AJTT-18-110 - Spark Plugs x6 (these will be Motorcraft AGSF 22FSCM)

You can go for the cheap 6-pack of coils and there does not seem to be much difference (if any) and since they should be replaced every 60K miles (IMO) the less expensive ones seem reasonable. Do not use anything less than platinum plugs.

I keep lists of part numbers and materials on my profile page. You can get there easily from my SIG.

Have fun
 

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2003 Mazda 6S
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Congrats on the purchase!

Good idea on the plugs and air filter. I'd also replace all 6 engine coils as well. They are well-known to go bad all the time on these cars.

The Duratec loves to leak oil. Common areas are valve cover gaskets and oil pan like a lot of engines, but the most annoying one is the timing cover gasket. I'd wager that's where your burning oil smell is coming from, as the cat runs right underneath. Replacing the gasket is a big job, basically everything has to come off the engine. It's almost not worth it unless the leak is really bad.

Keep a sharp eye out for any catalytic converter codes.
I have the same oil leak issue with mine. If I can ever find a spot where I can work on my car and not get at least violation LOL I plan on mounting something to the top of the catalytic converter to catch or redirect the oil away so that I stop getting the burning smell as well. Saw a picture on here one guy who did that with an old license plate
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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4,542 Posts
:eek: I'm stil running my orginals at 235k miles. :eek:

guess it's past time to change them...
That's how they should be.

I have the same oil leak issue with mine. If I can ever find a spot where I can work on my car and not get at least violation LOL I plan on mounting something to the top of the catalytic converter to catch or redirect the oil away so that I stop getting the burning smell as well. Saw a picture on here one guy who did that with an old license plate
Recently purchased 2004 Mazda 6 V6 at 105k miles
 
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