2004 standard shift with 142k miles. Have averaged around 18/20 mpg since AI bought the car new. The last 2 weeks the miolage has dropped to around 13/15 mpg. I have not noticed any reductionin power, or change in drivability. Weather has been cold - lows in 30's highs in the 50's but I never had this problem in prior years.

Will be going in for service in a week or so but would like to have some idea is this is happening to others.

Any ideas?

 

Check Plugs, check coils, check compression, not particularly in that order

what oil are you using, when was your last oil change? Premixing at all?

 

Plugs are due to be changed around 160k, oil is 5w20, the oil is changed every 3-5 k miles and I top it up regularly in between. no pre mixing.

 

is this the first time you are changing plugs? if so that could be the case.

 

could also be a dirty MAF sensor

 

I'm on my second set using the dealer recommended interval.

 

Ok but how many miles have you put on them?
OEM coils are known to have a short life

 

I believe they were changed at 60k and 120k. I'm not sure of the exact mileage but approximatley 4k miles ago at my last service the dealer looked at my service record and inidcated that the plugs were last changed at around 120k. I'm due for a service so I'll mention this to the dealer. I was just curious if this was something that people were noticing on a regular basis.

 

plugs and coils should be changed every 25k miles (some more often; some less). If you want to save some cash, do the job yourself. It really isn't too hard to do, and by doing it you'll feel more attached to the car
Also, I would recommend getting your plugs/coils/wires from BHR (black halo racing). They are much more durable than the OEM ones, and they should last the life of your engine...

 

I agree. I used to do it all myself but work has interfered with my time and I've gotten in the habit of letting someone else take care of it.

Thanks for the responses.

 

I agree with what everyone else said about checking spark plugs, coils, and even wires while you're at it. Also check the MAF sensor and air filter. My question to you is, are you still on your original engine with 142,000 miles?

 

Winter fuel as well Usually good for a couple of mpg. And more cold engine driving equals less as well

 

If your O2 sensor is failing, that can make a huge drop in milage. If you have 142K miles on your original O2 sensor, you might want to change it.

 

I bought the car new in Aug 2003, put a lot of highway and track miles on it for the first 100k miles and then took it off the tract due to concern about the high mileage. Will check the 02 and MAF.

Does anyone know of a good reliable independent Rx8 shop in the Sacramento area?

 

You may want to check the cat, (I don't think anyone mentioned that yet) the best way to do this is to pull it down and visually inspect it, anything other than a perfect honeycomb pattern is bad. You can tap the cat with a screwdriver and if you hear any rattling from inside the cat, then it is bad. If not, that doesn't mean it's not bad tho. The element could have fused together.

 

You don't need to replace coils every 25k miles.
That is an old wives tale.

Winter gas.
Longer warm ups.
Cat going bad.
Clean MAF
Clean air filter.
O2 sensor

 

you should know better. there's plenty of evidence to say otherwise. OEM coils ranging from brand new to 30K or so have been tested(properly) and shown to be junk. FWIW even Mazda's bogus test procedure has shown brand new to 30K coils as bad plenty of times. I kept record of mileage for a couple years and when I got rid of OEM coils @ ~30K the difference was astounding and also significantlymore than I ever got on OEM coils.

I'm not saying the OEM coils will keep the car from running smoothly. I'm saying they are barely adequate even when brand new. Thats not any debate around here, its common knowledge that has been tested, proven, and beat to death long ago

 

just being curious. does it have the original engine after 142k?

 

Yes the engine is original and still feels strong

 

are you getting any CELs? this might help us figure out whats going on

 

After all of the failure stories I have read about on this forum, it's nice to see someone who has taken their engine well beyond 100,000 miles. Do you mind sharing your maintenance routines? What type of oil used, premix or not, etc...

 

I have been very strict about sticking to the dealer schedule for maintenance. And have always kept extra 5w 20 oil at the house and in the car to make sure that it stays topped up between changes. the engin has not been modified although it has been run hard (lots of track days the first 100k) and lots of high rpm's since then just no track time. Other than that, no premix or anything other than premium fuel.

Based on everything I've read here, mauybe i've just been lucky or maybe the engine just likes to be spoiled. I wish I had some idea of why this one is doing so good but other than the very regular maint. schedule I can't guess. I'd like to get a couple of hundred k on it at least before I trade it, so we'll just have to see.

One other thing comes to mind. Early on the mechanic at the dealership told me to be very careful about always making sure that once I cranked th engin to always make sure it reached full operating temp before I turned it off. So even if I'm only pullin ginto the garage after washing it I take it oout for a spin to get everything running and hot. Of course I never have a problem taking this car out for a ride give the FUN factor!!

 

Running it hard is a good thing this engine loves to get beat on (After its broken in). I think to many people grandma their cars and this results in early engine failures. I had 124k on my original engine before I rebuilt it, overall the engine looked good. Hopefully I can get another 50k out of it

 

what is a good aftermarket coil for the rx8 that is ready to bolt on where the factory ones go? I do not want to spend a lot of time and energy into relocating them but reading the posts about them makes me wonder.

Thanks for the input

T

 

A word of caution - if it is your plugs/wires/coils going bad, then your reduction in mileage is due to unburned fuel (duh). The unburned fuel can kill your cat. This happened to me (although I can't 100% prove the correlation) - bad coils not immediately dealt with led to a clogged (melted) cat shortly thereafter.

Just something to think about...