8_wannabe

What they do is refer you to your dealer for a fuel consumption test. That consists of your dealer keep the car several days/up to a week and driving it around with instrumentation attached to verify mileage. Not sure what they do after that. Two of us (at least) have gotten this story.

jd62

We just got back from a trip from the DFW area to Chicago and back. Air was on all the time except for a few hours one morning. We averaged around 21 mpg. The best we got was a little over 22mpg when the air was off for about 1/2 tank. At least it's better than the 13 we've been getting in town.

I put in 1/2 quart of oil at 1300 and the other half at 2600 to keep the oil level light from coming on at high speed.

TJRX8

Ayup True dat!

TJRX8

What is considered high speed that your oil light is coming on?

poison123

Ya know it'd be interesting to see a Dyno of someone getting good gas mileage. Gotta wonder what their HP is and whether their dyno will have a Dip in it around 6700rpm.

BillK

You do know that that right there will take a big bite out of your highway mileage, right?

Remember, mileage at highway speeds drops off sharply above 60 MPH; the much-maligned 55 MPH speed limit wasn't chosen by throwing darts at the wall.

Run a tank on the highway at no more than the posted speed limit and see what you get...

jd62

The oil level light came on at about 78 and went out after slowing to about 74. The level on the dipstick was about 1/3 down from full.

TJRX8

I have about 1700 miles and just checked the oil again. It is right at half and I haven't added any yet nor has the oil light come on.
BTW I get it up to at least 80 everytime I take it out.

jd62

I think the later VIN cars have better baffling in the oil pan. My VIN is 2178 build 6/3 and I think I have the old oil pan which causes the oil light problem.

TJRX8

10xx VIN and 5/28 build. hmmm now what?

Anyway another fill-up today:
13.3 gallons and a whopping 214 combined miles traveled:

16.09 MPG and climbing

TJRX8

Posted speeds are 70-75, maybe that's my problem. I need to see if Jeb will lower the speed limits again! :D

RX-GR8

It's good that it's climbing. Weird that some cars start out with good MPG right out of the shoot while some have to "age". If all things were equal we could point to the ECU potentially assuming average driving patterns and obeying the break in period, etc. as being the culprit and holding the engine back until it was loosened up but that doesn't seem to be the case. Also at 2,000 miles things seem to really get interesting around 6000 rpm in terms of power. Keep us posted.

loco4rx8

Isn't it possible that the older cars in the first allocation that sat at port for a few weeks were flashed with different ECU settings than later production cars? Maybe Mazda has come up with new, "better" settings after having a little more time to test/tweak.

I just wonder if that would help explain the differences we're seeing in mileage figures. My car was built 6/23/03 and so far I have been getting 22-23 mpg consistently after 19 the first tank. I've been driving pretty aggressively the last couple tanks and my highway speeds vary anywhere from 60-80. My daily commute is 80/20 highway/city, and I've got a little over 1100 miles on the car now.

RX-GR8

Yes I agree this is a good explanation. I was looking at it as a static ECU for all cars but Mazda might be tweaking it as it gets more and more feedback.

8_wannabe

Interesting good or interesting bad? I've had crappy gas mileage up till now, but at 2000 miles seeing my mileage start to improve. I have NOT had that power loss above 6250 that some have reported. Please don't tell me I'm gonna start seeing a power loss!

(btw, I have not been guilty of accusing people of inventing the 6250 power loss or not knowing how to drive. I wish those without the mileage or a/c problems would stop accusing those less fortunate of making this stuff up. It is really getting tiresome. This rant is not directed at RX-GR8, but many others in this forum.)

RX-GR8

Interesting good. Sorry I should have been more explicit. I read on this forum some owners stating that at about 2000 miles the power seemed to increase at 6200 rpm whereas before the port seemed to be stuck or there was hesitation..

8_wannabe

I think these people had a power problem at 6200 and ultimately the problem goes away. Since I'm not seeing that problem there should be no change for me. I think these theories about different versions of the ECU sound pretty plausible. This is the type of mystery I hope BOOSTD7 can unravel in his investigations with Mazda. If I have a substandard ECU burn, I'd like to know (1) Will my ECU sooner or later behave like those who are getting full power and full mileage, or (2) Can they reprogram my ECU to more favorable mpg's like some people seem to be getting from Day 1.

SPEEE DE

I am feeling your pain. I am keeping track on my latest fillup but its been awful so far. I've got about 500 miles on it and am beside myself on how bad the gas is. I would think the aluminum hood and pedals would push this thing to at least 40 mpg, don't you? Thats a joke.

Seriously, I demand at least 20. I will be gripping to the dealer too if I cant get it to at least 17. Below that is embarrassing, no matter how you drive. And I drive pretty conservatively.

I will look at the manual for the shift points though. But what fun is that. If I wanted some dang robotic shift points, I would have bought an automatic.

8_wannabe

In desperation when I was getting 15 mpg I started following the recommended shift points, namely shifting at 3000 rpm. It was awful, just like you said. I did it for one full tank, got 16 mpg, did it for another half tank before I said the heck with it. It TOTALLY removes all fun from having the 8, for a gain of 1 mpg? I don't think so.

Now, I'm back to my old ways, but I've learned new bad habits (like efficient driving ). I often shift now at 3K and I don't mind it so much anymore, but whenever I feel like it I rev it higher, meaning several times on any given outing. My mileage continues to rise (now up to 17.5.)

I am convinced that poor mileage has nothing to do with "bad" driving habits (within reason.) I've read many posts from people who regularly rev to 6K and are getting above 20 mpg without even trying. There are two versions of this car out there: Low mileage and high mileage. If I had to bet, it has to do with the ECU. I think we will get to the bottom of this, hopefully within the next few weeks (are you listening, Mazda?) because the polls on this forum show that more people are concerned about poor mileage than about less hp on paper. I would bet more cars will be returned for the mpg reason than for any other unless Mazda can help us sort this out.

astrlsrfr

On the money 8_wannabe, as usual.

Gotsta be the ECU. Its the most plausible explanation, given the total confluence of info: the port hangup, the HP drop, and the drastic varation of MPG amongst different 8s. I wish knew how to check the firmware version. And, of course, I wish we knew how to flash it.

We creep closer and closer to October 1st, and Mazda continues to seemingly pretend this is not a problem. No recall. No TSB. Not even a quiet word to the dealers. They either don't understand the problem themselves, or they are living a fantasy that 8 owners don't really care about the MPG as much as this forum indicates they do, or they have already fixed the problem in new 8s, and are going to quietly let the buyback take care of the issue. I'm thinking its the later.

Since my car is one of the "sick" ones (and I don't mean "sick" in the newish positive form of the word . 13 MPG is the norm for my 8), I am leaning heavily in that direction. I will wait until the last week of September. If there is no fix at that time, my car is going back.

Great car. Lots of drama. This has to be one of the most fascinating new car experiences I've ever had. I am very happy to have the internet, and this forum. Think how screwed up all this would be if we couldn't communicate like this.

BillK

Well 75 is still lower than 85, so run a tank no faster than the posted limit and see if it makes a difference...

mmjames

I drive on highway about 60 % of the time at 70 - 90 mph, and in the city at normal speed. I accelerate quickly a lot of the time, and run the A/C in 90 + weather all the time. I have about 700 miles on the car and I have been getting about 200-mpg average each tank of 91 gas. Just giving the facts for me.

poison123

So your getting what 12-14mpg, thats friggin terrible.

mmjames

The mileage sucks but I did not buy it for the mileage. I love the drive and I do not give a damn about the mileage. I have a economy car for that. So your right the mileage sucks, but I love it anyway :D

red_rx8_red_int

That may not be true. It depends how low he's letting the tank go. I also have a little over 700 on my car and have been filling up about every 200 miles (when the meter is around 1/4 mark).

200 miles--11.696 gallons = 17.09 MPG
220.1 miles--12.551 gallons = 17.53 MPG
200 miles--13.055 gallons = 15.32


The big drop was due to hitting 600 miles on the car and bouncing off the rev limiter frequently :D


Edit: The first tanks were not granny style driving. Reasonably hard acceleration but less than WOT and shifting just under 6K RPMs.