Hi,

I have 2009 automatic RX8 with about 52k miles.
Commuting to work with 60% highway/40% city, I can only make 200 miles with a fuel tank, that's 12 to 13 mpg !!!

When I bought the car with 41k miles, the mpg wasn't much better, but I noticed recently it got worst. I guess spark plugs are not lasting very long.

Also, I have been complaining about the poor power of this car, but I had no other RX8 to compare, I thought it was just the regular power. Now I think something is wrong.
Also the engine sounds hard to start every time, even though it takes 2 sec to start. But it is emptying my battery quickly.

Ok, I read another thread about someone complaining about the same mpg, so I plan to change de spark plugs myself.
Do I need to change the wire ?

What about the spark coils, how do I know I have to change them ?

Any other things to check or replace to improve the mpg ?
I will take a look inside the air filter, but not sure I can do much things on it.

 

how exactly are you calculating 12-13mpg ... i get about 220miles to the tank and after doing some calculations over time this is about 16-17mpg for me. When was the last time the spark plugs were changed.

Go to your local auto store and have them check your battery ... battery drain can kill gas mileage as the car would be hard pressed for keeping data in memory like fuel trims, etc.

Lastly, you can easily check ignition coils, as that is also a cause for poor starting performance, with a spark tester found at your local auto store.



https://www.rx8club.com/do-yourself-...-wires-222641/

 

If you are at 52k and have never changed your air filter(or know the previous owner never did) then you are way past due for that, same with the spark plugs. Your spark plugs should be changed every 20-25k miles, some people even change them every 15k. They usually get pretty crusty looking around 20k miles.

 

And not just the plugs. Failing coils and/or wires will kill your plugs quite fast as well.

 

MPG..so much depends 'how' you drive the car as we know..

Ignition analysis should always first start at the source, the Battery, a poor battery not holding a charge (strong CA) is going to result in a longer start and weaker spark/firing.

So get Battery tested first....if needing renew with a good quality battery, if it is original then 'roughly' due for change....You can check fluid level in battery...any there covering plates?

As Paimon said..how long ago were the Spark Plugs renewed?...if ever..

If not, definitely change them and then get back.

Fresh plugs can make a world of difference, and yes, you are also close to having Air Filter renewed...I would also do so.

How long ago did you have an engine oil and filter change?

Edit: So far I have yet to see any Series II with 'B' Coils 'fail'.....I would do these other tasks first and then look at Coil/Wires.

 

Thanks for replying so quickly!
The way I drive, well, people told me I baby drive the car, that's right I think.

I don't even know if the sparks plugs was changed before actually, nor the air filter, nor the coils.
The oil and filter is changed every 4k to 5k miles, and I add some oil when needed.

Regarding the battery, its difficult to say, I charged it a couple of times. After 2 weeks of no-use the voltage gets about 12.4v. After charging, it stays at about 12.7v for several days.
But when I crank the car in the morning, it seems to be low power.
I think I will change the sparks, coils, maybe wires, then the air filter. If the engine is hard starting I will change the battery.

 

NewSV, it looks like you have a lot to learn about our car. I'd recommend the New and Potential Owners thread linked in my sig.

For this car, you baby the transmission, but baby the engine and it will die an early death. You might also be HEAVILY carbon fouled, seals, plugs, injector ports, etc... Once you get the new ignition in, take it out and give it a serious wankle spanking.

And if you aren't using synthetic, then your oil is only lasting about 2,500 miles (proven by oil analysis in our engines), and you are way too short on viscosity by 4,000 miles of your interval. Switch to synthetic or cut your change interval in half.

 

Alright, I came back from oreilly autoparts, the guy told me he worked for 6 years in Mazda before, and said there is no need to change the coils, except if really needed, and the original ones are very good quality.

I will check online a way to test them.

i got my spark plugs in the meantime.

 

Redacted, Listen to Ash. I didn't notice that this was Series 2 area.

 

Alright, I just want to take care of my car, I am not trying to deny anything. Also the seller didn't even ask me my mileage before telling me that..
After reading many threads about it I will go for the change.

Any brand to recommend ?

In oreilly auto part I found the "Import Direct" for $37/ea

List: Coils - Ignition - 2009 Mazda RX-8 | O'Reilly Auto Parts

Should I change the wires as well ?

 

Why do you continue to not recognize that the 75% of OE failed coils are the plain # or original bad Coils and another 25% of S1 with the A part number iteration (all cars made between 2003 and late 2007), only the last 6 months of S1 production had the B Coils also used in updated Series 2's of 2009~.

Plus ANY Mazda Part which has an interchangeability code of 'A' (different meaning again to A or B or C at end of OE part number) which means ""New part is fully interchangeable with Old from a technical or physical standing but Old part is not interchangeable with new part"" for a parts interpreter point of diagnosis. (we know they will all fit and work, but Mazda warns not to use old new Coils in a car meant for new Coils).

This all means there has been physical change to said part, in the case of the Coils to the Coil internals or materials used, as the external design appearance is identical, apart from Part number ID stamped on side of coil., A, B or C. (the end bit of OE Part Number)

OE RX-8 Coil History

N3H1-18-100 used on all RX-8's up to 1st March 2006.
N3H1-18-100A 1st March 2006 to 1st December 2007.
N3H1-18-100B From 1st December 2007 to 5th Sept, 2011
N3H1-18-100C From 5 Sept 2011.

All have interchangeability code of A, New for Old , but not old for new.



I do not disagree with you about engine replacements being done unnecessary when it was a case of bad Coils in the early years.

 

Now having said what I said to my fellow moderator RIWWP..

And your 2009 Series II car does not have the old Coils which gave all the issues....however....

Your car is getting up in miles, we (I) have yet to see any 2009~ saying that Coils have failed, but, from an exercise point of view, if you want to, I would try the following first...

IS your Battery 100%???, if so...

Change Spark Plugs, wires if you must, Air Filter is due, and perhaps give her an Oil and Filter change.

Put all that in and see how she starts and runs...

If you believe that it is still not starting as it should or engine performance is poor, then look at renewing Coils, as Paimon said there is a good little 'coil' tester (the tester part they now supply is slightly different to his pic, see red card unit below, is the latest sold now).

Don't cheap out, Mazda in USA are apparently now selling the later RX-8 Coils, the C iteration, these are the latest and 'greatest', but are about $66 each.

To be honest, if it was my car and done close to 60K miles, I think I would also do the Coils, but I would still like to do a A and B test...

Put it all together on existing coils and then start run/ drive car, get a feel (backside dyno), and then renew to new Coils...

Just to satisfy my curiosity...which you don't have to do..



Edit: I see your link offers a 'Limited Lifetime Warranty' ....what is the 'limited' part of it?

This below is the Coil tester now supplied, a little more safer from catching a hight voltage boot!....not expensive, under $10.

 

Your point about this being a 2009 having the C revision is a good one. I will have to watch out for that. To be honest I didn't even notice that this thread was in S2. My apologies.

NewSV, listen to Ash for advice on this. Ignore what I said. My point applies to the Series 1 far more than the Series 2. Your coils may indeed be fine.

 

For those interested and not certain what OE Coil you have installed in your car, once removed, the black Coil side body either has a A, B, or C or nothing stamped on the side of it.

See the original Part Number and vehicle production date list above to match date to coil 'letter'.

I am talking OE supplied Coils only.

 

Alright, I finally changed my spark plugs.
However I noticed the previous ones are NGK too, which means the previous owner changed them before I guess... In fact I wouldn't be too surprised, we can say the guy took care of his car before.

The question now is, was it really necessary to change them then ?

Here are the spark plugs, what do you think about them ?

 

Unless the plugs are broken, the only metric that should ever change is the gap between the electrodes. However, keep in mind that some kinds of ash can interfere with the spark, and since rotaries sweep the metal seals past the spark plug openings, I'm betting at least a little bit of that ash is made of iron. So the gap might not be what you think it is if you jam a gauge between the electrodes.