Bad gas mileage. Want to try updating ECU firmware but Mazda wants $95.

[shawnmos]

So I have been getting pretty poor gas mileage compared to most people's MS3. Recently I took a 600mile trip which was mostly on the interstate with windows up and AC off. I only got about 24mpg.

I was talking to one of the salesmen at Mazda when I bought my wife's 2. He owns a heavily modded MS3 pushing out over 25 psi in boost and he says he gets over 30mpg on the highway. He thought maybe an ECU update would fix the problem.

So I brought it into the service department figuring I could just have them update the ECU and be on my way, but they told me because it was out of warranty it would be $95 to update and if it turns out I already had the latest version I would still have to pay them the $95. (pissed)

I already had the car in few times because of this problem and they didn't find anything wrong. Eventually I got a CEL. Turns out the O2 sensors went bad and they replaced all of my O2 sensors under warranty. Usually when there is a CEL they update the ECU, so I asked if they updated the ECU then (about 2 years ago) and she looked it up and she told me that they didn't. (braindead

Obviously my car is running rich and I don't know why. Does anyone know if there have been any updates for the ECU in the past few years and if so if there is somewhere I can get the update for cheaper? I have a feeling if I don't get this problem fixed I'm going to end up with another set of fouled O2 sensors.

Thanks!

 

[rsvinylgraphics]

I think the salesman you talked to may have exaggerated a little bit. At 24, You are pretty close to the avg highway mpg rating of 26 however. Have you looked into the Hypertech Max Sport tuner?
It can increases your mpg by a few mpg's that is if you can keep your foot out of it.

 

[zoomzoomMSP]

with my current setup which you can see in my SIG. i went on a nice trip with the wifey and was pleased with a 28 MPG Average. currently with normal everyday driving im seeing 21-23 MPG's. the HyperTech did help with the MPG's and so did my Intake........ but it also makes you wanna drive harder which tanks the MPG's. depending on your mods and your driving style the average can be pretty big.

 

[shawnmos]

No mods, car is bone stock (except for the radio). I used to get around 13-15mpg around town, but now I get about 16-18mpg after changing the spark plugs. I think the old ones had gotten fouled.

Car has 34k miles. I changed the spark plugs, air filter, (and front brake pads ) at 30k. The O2 sensors went bad and were replaced at around 16k miles.

I'm pretty sure the car is running rich and I'm just fixing the symptoms. I haven't found the cause yet. I would like to rule out an ECU issue though. Is there a list of ECU updates somewhere?

Also, what would the Hypertech tuner allow me to do? Seems pretty pricey.

 

[MikeHTally]

Not difficult to get 26-28 mpg on the highway. The best mine has gotten was during break-in. We went on a road trip of 900 miles or so. It got 30.3 mpg while on the outbound leg (lower speeds, higher gears loading the motor more). The return trip passed the mark I had set as break-in was over, so I drove faster and got 28+ mpg. I don't drive "city" miles at all. More suburban and rural. My mileage is in my sig.

 

[meicalnissyen]

I think the salesman you talked to may have exaggerated a little bit. At 24, You are pretty close to the avg highway mpg rating of 26 however. Have you looked into the Hypertech Max Sport tuner?
It can increases your mpg by a few mpg's that is if you can keep your foot out of it.

please, allow me to rephrase
the salesperson is a ****** liar
I have noted an interesting thing on this topic

real world owners get 25, at best, on the freeway
thats like, resetting the ecu prior to jumping on 75 from tampa to portcharlotte and back, keeping it out of boost, etc

Now, that said,

some trustworthy folk claim 30.....
but, upon further query, i find, to a man, 65 instead of freeway speed, and, no mods,...... at all

numbers based on dividing miles driven/gallons pumped

using the number on the gizmo is as irrelevant as his opinion

 

[MikeHTally]

please, allow me to rephrase
the salesperson is a ****** liar
I have noted an interesting thing on this topic

real world owners get 25, at best, on the freeway
thats like, resetting the ecu prior to jumping on 75 from tampa to portcharlotte and back, keeping it out of boost, etc

Now, that said,

some trustworthy folk claim 30.....
but, upon further query, i find, to a man, 65 instead of freeway speed, and, no mods,...... at all

numbers based on dividing miles driven/gallons pumped

using the number on the gizmo is as irrelevant as your opinion

"... using the number on the gizmo is as irrelevant as your opinion." You're learning. The computer is so optimistic as to be useless (7%-14%). After mine got that 30+, that has not happened since (I normally can't drive that slow - who drive 55 on the interstate? ). If click my "Fuelly" sig, you'll see the best was 28.9 mpg. That was on a run to Gainesville at no more that 75.

As for the HyperTech, it'll take a while to recoup the expense. It would probably take me over two years just to break even.

 

[meicalnissyen]

EEK, my cursor jumped again

I had intended to type
"using the number on the gizmo is as irrelevant as his opinion" meaning the salesman
sorry, that read badly

 

[blue-sun]

Ive taken my MS3 from Chicago to Detroit twice since I bought mine. Both trips I was able to see 30-31MPG. My car is stock other than a Mazdsspeed CAI. Calculations were always done based on filling my tank up and zeroing out my trip meter then doing the math based on my next fill up at about 1/4 tank. I consistently was going 75-80 most of the way, saw 100 many times and had the AC on the entire time. This was both there and back on both trips. Something has to be the problem for your poor MPG's.