Terrible Gas Mileage - Please Help

[DRS211]

Hi All,

My 2008 CX-7 turbo AWD is getting terrible gas mileage after I just had the top half of the motor rebuilt. At 109,000 miles, the timing chain broke and bent all the valves, etc. I had the engine fixed at a reputable shop (almost $5K to fix) and now the car is only getting 18mpg highway when it uses to get 25 + mpg.

The check engine light came on just last week, and after diagnostics, it is the up-flow 02 sensor. Could this be the reason I am getting such terrible gas mileage? I just ordered the 02 sensor from oxygen sensors 123 website for $165 and I am going to install tomorrow. I was hoping I could find some “how to” instructions on this site for the 02 sensor change. Anyway, thanks for any advice.

Danny Sottile

[Hectik1]

Could be the o2....were the plugs changed?

How long ago was the motor rebuilt?

[DRS211]

Originally Posted by Hectik1 Could be the o2....were the plugs changed? How long ago was the motor rebuilt?

Hi,

The motor was fixed about 2 months ago. It was getting over 25mpg until the timing chain broke and the top half of the motor was destroyed. New exhasut/intake valves, re-decked head, etc..I will have to ask the garage if they changed out the plugs. I have the new o2 sensor and will install tommorow. If that does not help the problem, I will order a new set of plugs. Thanks for the input!!

Danny

[Hectik1]

I was going to say if it was recent, that the timing may be off. Don't know of the CEL will turn on but if the timing is wrong, it can cause the drastic decrease of fuel mileage.

How does it feel as far as acceleration, etc?

[trf5000]

Yet another example of how fickle these motors can be. Most likely something wasn't put back together right. IMHO, its always best to let someone who is very familar with these particular motors do the repair work. It might cost more in the end, but at least it is done right the first time.

[DRS211]

Originally Posted by Hectik1 I was going to say if it was recent, that the timing may be off. Don't know of the CEL will turn on but if the timing is wrong, it can cause the drastic decrease of fuel mileage. How does it feel as far as acceleration, etc?

The acceleration is fine and the car runs as good as the day it was new, just the fuel economy is less 8 or so MPG. If the timing is off from when they replaced the valves, etc. would the engine be missing and experience lag throughout the power curve? Do you think I should take the car to the Mazda dealership and have them check the timing?

Thanks Hector!!

Danny

[Hectik1]

I think it has to do something with the timing. It could be off a little and you won't experience anything noticable. I would have it checked out.

[Raider]

18 MPG with AWD, in the cold, is good. Usually around 15 or so in the winter. Also, ethanol sucks, kills MPG too.

Get the CEL fixed for sure.

[07CX-7KID]

Its not the timing. If it was off a tooth the CEL would come on and it would be miss fire on all cyl. It is most likely the O2 being out.

[aviator79]

25MPG. WTF. I get 14.

[Shortymazda]

I would also go for the o2 sensor, I did the timing in mines and it was off by a tooth,no CEL came on but at WOT on the highway you could notice it a bit. Hope this helps.

[rodney5579]

I just bought my 2011 turbo and it seems to get about 18 combined

[lildisco]

Make sure you use premium to get optimal performance & mpg's. I find i get better with shell gass than any other brand near me. There is a difference between 91 octane & 93 octane. I try to get the highest possible at each station.

[Ian0611]

What's a normal mpg range for the CX7? We just got ours a couple weeks ago and I was hoping it would do better than our Murano but so far we're only getting about 17-18mpg combined.

[lildisco]

that seems to be around the norm for most people. All depends on your driving habits, what type/brand of gas you use, tire pressure, etc.....

[lvdukerider]

I've owned my 2010 GT FWD since July 2010 18 to 19 is about the best it ever gets. That's about the only downside I can find with the car, oh well I guess that's the price we pay to drive something that isn't a slug. The thing that gets me is my wife's 2013 KIA Optima SXL 2.0 turbo puts out 274 HP and gets in the low to mid 20'S on regular unleaded around town. Why can't Mazda do that?

[Ian0611]

Originally Posted by lildisco that seems to be around the norm for most people. All depends on your driving habits, what type/brand of gas you use, tire pressure, etc.....

That's a little disappointing. Part of the reason I liked the CX7 to begin with was it's suppose to get better mpg than the Murano. Not by much, but hey every little bit counts. Well at least it's no worse. I guess this just means I need to start tuning it sooner

[tommydorsey]

I'm definitely doing better than 18-19. Not much - probably 19-20. Definitely noticed better mileage with premium gas.

Jim

[Ian0611]

My wife just filled up last night and we only got about 15mpg on 93 Oct. on the lat tank. Do the CX7s tend to get a lot of boost leaks? What else could be causing bad mpg if there aren't any CELs??

[Raider]

Cold? Check
AWD? Check
Ethanol gas? Check
91+ Check

15 MPG is normal.

And this has been a discussion since 2006, it is normal.

[Ian0611]

Originally Posted by Raider Cold? Check AWD? Check Ethanol gas? Check 91+ Check 15 MPG is normal. And this has been a discussion since 2006, it is normal.

Bummer man! Like I said, I really was hoping for better than that out of a turbo 4. Our Murano was AWD with a V6 and usually got 17-18 even in the winter.

[Raider]

Well, Versatune can tweak it and help squeeze out mpg.

[Ian0611]

Originally Posted by Raider Well, Versatune can tweak it and help squeeze out mpg.

Yeah that's the plan. Will probably have to wait until after the holidays though.

[mrbrace]

Yeah my wife gets 20mpg if she is babying the crap out of it.

[Ian0611]

Originally Posted by mrbrace Yeah my wife gets 20mpg if she is babying the crap out of it.

Have you had it tuned at all?

[mrbrace]

Originally Posted by Ian0611 Have you had it tuned at all?

Where would be a good place to have it tuned? Also I am considering a TMIC and a BOV/BPV hybrid that turbo-kits.com puts out...

Anyone know of any intakes that are CARB certified for Cali?

[Ian0611]

I'm trying to get a group buy set up with Versatune as we speak. You can download their software and they have some basic tunes that you can upload yourself if you're not in to custom tuning. Otherwise I think their are a couple of guys on here that do custom tunes but I don't know their names off the top of my head.

[mrbrace]

Originally Posted by Ian0611 I'm trying to get a group buy set up with Versatune as we speak. You can download their software and they have some basic tunes that you can upload yourself if you're not in to custom tuning. Otherwise I think their are a couple of guys on here that do custom tunes but I don't know their names off the top of my head.

Ya the versatune is something I am interested in, know if it has some default tunes since I am not well versed in the turning and what needs to be what? Basically do they have preconfigured settings already?

[Ian0611]

Originally Posted by mrbrace Ya the versatune is something I am interested in, know if it has some default tunes since I am not well versed in the turning and what needs to be what? Basically do they have preconfigured settings already?

Yea they have some preconfigured tunes for some basic set ups that you can download. You don't really need to know much about tuning to use those.

[mrbrace]

Originally Posted by Ian0611 Yea they have some preconfigured tunes for some basic set ups that you can download. You don't really need to know much about tuning to use those.

Sweet! My wife thinks I am crazy but I have always wanted to upgrade a turbo charged vehicle and this is our first one...pretty excited lol

[Ian0611]

Originally Posted by mrbrace Sweet! My wife thinks I am crazy but I have always wanted to upgrade a turbo charged vehicle and this is our first one...pretty excited lol

Lol!! My wife thinks the same thing but she understands a little bit more because I already have an Evo. When I told her I was going to start tuning her CX7 she just rolled her eyes and shook her head lol

[mrbrace]

Originally Posted by Ian0611 Lol!! My wife thinks the same thing but she understands a little bit more because I already have an Evo. When I told her I was going to start tuning her CX7 she just rolled her eyes and shook her head lol

Definitely understand that...my wife even said she would spring for it if it gives her better gas mileage..hehe, what she doesn't know won't hurt

[Ian0611]

Originally Posted by mrbrace Definitely understand that...my wife even said she would spring for it if it gives her better gas mileage..hehe, what she doesn't know won't hurt

Yea that's actually the main reason I'm doing it. I probably won't be doing any mods any time soon because we have an extended warranty. But I know that even stock, a tune can do wonders for these cars. A good tune should definitely squeeze out a couple more MPG so the tuning will eventually pay for itself and make the car more fun to drive

[lildisco]

I'm averaging over 20 mpg with mine. It all depends on how you drive. I know when my wife drives it, the mpg's go down to around 16 in the city. When i drive it in the city i get 17-18. Best highway run i had was 24.xx on a trip to Tennessee last year. I'm using 'Waynes Tune' on Veratunes forum atm. There isn't much available as far as 1st gen pre loaded tunes, but the more people that get it, the more will show up.

Another thing is that the 7 is a heavy ass pig. It takes a lot of muscle to get'er going from a dead stop. I try not to stop as much as i can because of this.

Also, try to find the highest octane available to you. There's a huge difference between 91 & 93, about 2-3 mpg's when i was on the stock tune. I haven't been lower than 93 since the tune. Shell in my area tends to give me the most mpg's.

[Ian0611]

Originally Posted by lildisco I'm averaging over 20 mpg with mine. It all depends on how you drive. I know when my wife drives it, the mpg's go down to around 16 in the city. When i drive it in the city i get 17-18. Best highway run i had was 24.xx on a trip to Tennessee last year. I'm using 'Waynes Tune' on Veratunes forum atm. There isn't much available as far as 1st gen pre loaded tunes, but the more people that get it, the more will show up. Another thing is that the 7 is a heavy ass pig. It takes a lot of muscle to get'er going from a dead stop. I try not to stop as much as i can because of this. Also, try to find the highest octane available to you. There's a huge difference between 91 & 93, about 2-3 mpg's when i was on the stock tune. I haven't been lower than 93 since the tune. Shell in my area tends to give me the most mpg's.

I'm jealous man!! Ever since we got the CX7 back from having the VVT done we're only getting about 13mpg (city). We only use 93 but I've been questioning the quality of gas around here lately because the MPGs in my Evo have been down as well. But still... I think 13MPG is ridiculous!! I'm also seriously considering taking it back to the dealership to have them double check their work because something just seems off and it feels like performance is down as well. I need to get Versatune soon so I can get a better idea of what the problem is.

[lildisco]

To my knowledge, my vvt hasn't been done. I guess i should check with a dealer to see if it has been done. If the vvt hasn't been done, i'm scared about mpg's & performance. Only time will tell

[Ian0611]

Originally Posted by lildisco To my knowledge, my vvt hasn't been done. I guess i should check with a dealer to see if it has been done. If the vvt hasn't been done, i'm scared about mpg's & performance. Only time will tell

If it's not making a weird rattling noise on start up then I wouldn't worry about it. I'm thinking when they did mine, it either had a tune on it and they flashed it back to stock or they didn't get it timed properly, or both.

[lildisco]

There's a few ecu updates too. My 7 is around 59,000 so it still could go bad. Also have the extended warranty so i'm pretty well covered on all counts.

[aviator79]

Ya, I get 13-17mpg. Trying to figure out the problem. Got versatune and no better. MS6 avg 23mpg and I know I shoul det like 20mpg on the CX-7. Figure its bearings or O2 sensors but really no idea...

[torquemaniac]

Originally Posted by aviator79 Ya, I get 13-17mpg. Trying to figure out the problem. Got versatune and no better. MS6 avg 23mpg and I know I shoul det like 20mpg on the CX-7. Figure its bearings or O2 sensors but really no idea...

Hello Aviator...did you do some tuning on the CX-7 since you got Versatuner, or did you just use the pre-set tune?

FYI, I get between 15-18mpg, but I drive it like theres no tomorrow, and I run a load of 2.0 betweeen 3000 and 5500rpm

Ive seen in the earlier post that a Kia 2.0 turbo has more HP and better mileage, even with the smaller engine and the use of 89 octane fuel...thats interesting...Ill have to look at how they manage to do this!!!