oakley1984

So ive searched the forums and have read a few threads in regards to poor fuel economy, most of which have the answer of "change your driving habits"

I will flat out say, yep, got a heavy right foot, have np with accepting the loss in fuel efficiency in that regard. However, my driving habits have not changed, yet within the last ~2mo my fuel consumption has gone up ~30%

I have an '11 g37xS coupe with ~103,000km. The car is due for new plugs (have them, have yet to install) had considered that the cat's might be plugged, but considering i generally sit at 4-7k rpm it seems doubtful, recently though i have noticed the exhaust smells rich. my best guess is (and dependent on result of replacing plugs) is that maf's are due for a cleaning/replacement, and o2 sensors should be replaced (functional or not, i drive the **** out of my vehicle.) im sure i should also be replacing fuel filter... .is there anything else i should be looking into ? i am quite adept mechanically but am also unfamiliar with the engine, and its always better to ask than assume.

Surfnazi

Change all fluids plugs filters

stealthee

The temperature is colder, warm ups, and winter fuel is going to kill your fuel mileage.

I went from over 27mpg to under 24mpg this winter.

slartibartfast

iTrader: (7)

I'd start with the O2 sensors. You are apprently not going into closed loop.

PNW_IPL

iTrader: (5)

What's your mpg? Mine sits between 11 and 13. My 350z nismo stayed around 12 and 13.5. My guess it's fine and based on driving style vs issues. Nismo is at 40k miles G is at 43k miles.
both on stock plugs stock sensors both with ART pipes and long tube cold air intakes and full CBE.

canucklehead

iTrader: (9)

+1 to the poor winter fuel consumption. the OP is likely Canadian since he reported metric vehicle mileage, not sure where, but unless he relocated to the southern US, winter plays a big part of reduced economy.

winter gas formulations differ from summer gas, increased use of accessories, warm ups & idling, etc, all add up to hit hard on consumption.

i've owned my g37 for ~7 years in western Canada - Vancity. even with our mild winters, i typically see ~10-15% consumption increase.

as others mention, do a full service for preventative maintenance items to get you running optimally. unless you are throwing any codes, the balance of economy reduction likely lies with the season and you should be back to normal by spring.

Surfnazi

Or stop sipping troll juice

Baadnewsburr

iTrader: (3)

These are good points, I don't switch gas, but my winter tires alone make me lose about 12% every winter

but to the OP, driving between 4-7k on the regular seems to be killing it...i'm no gentle driver and I have the old 5 speed auto and I'm still only between 2700-3500 in my long-a** commute

oakley1984

thnx to all who have replied,
will do my best to address all who have commented,
@surfnazi: Change all fluids plugs filters
since ive had vehicle, oil changes have been done @ 3500km intervals with royal purple & denso/mahle oil filters (will not run fram filters.)
changed front n rear diff oil, last remaining for oil changes are trans & transfer case

thnx to all who have mentioned the winter fuel formulation, had not considered...

mileage for those that have mentioned, 16.6l/100km or ~14mpg

will add o2 sensors to list of things to change...

no codes being thrown, had the vehicle go into limp mode once with the codes of P0021 & P0524, after clearing codes, changing oil& filters, has yet to return after ~7000km/5000mi with regular high rpm... (expanding on that, only happened once, after parking car on a steep incline)


@ slartibartfast care to expand on "not going into closed loop" ?

end note, i have new plugs to install, short of trans/transfercase, all oils have been changed and maintained meticulously. will add o2 sensors to list for next maintenance

@surfnazi... smoke some more crack bud.


to the rest, ty for the feedback!

slartibartfast

iTrader: (7)

At idle and full throttle, the ecu ignores the O2 sensors and cares little for emissions. The object is to keep the engine running. This is called open loop. Idle needs to be rich to keep the engine running and full throttle is rich to protect the engine.

Closed loop occurs everywhere else in the engine operating range. O2 sensor information and learned alpha enter into the fueling equation, among other things. Emissions and economy become the priorities.

I'm sure Wikipedia has a nice page about this subject if you wish to investigate further.

canucklehead

iTrader: (9)

^ dude, you may have a problem there. those are the codes i had when my rear timing cover gallery gasket failed. i too cleared the codes 2 or 3 times over the course of a year before i realized what the condition was that was triggering the codes. as soon as i found out the root cause (low oil pressure due to blown gasket) i hurried into the dealer for a repair under warranty.

food for thought, those codes may mean a serious issue that needs your attention.

lots of info on the forum:
https://www.myg37.com/forums/engine-...and-p0524.html

PNW_IPL

iTrader: (5)

good info there man!!

oakley1984

I was super concerned when it first happened, did all the research i could on the issue, had a friend whos got a snap on scan tool, we went through the full test procedure and everything passed, oil has come back clean, no particulate, no sign of gasket pieces, nothing. only happened the once after i parked my car on a steep incline. no loss of power, no signs of burning oil, vvel seems to be functioning properly
(im a former mechanic by trade...) im just unfamiliar with the specific nuances of this engine/vehicle as ive never worked on one. have done my due diligence of checking regularly for symptoms and reoccurances of issues and have not seen a single one after ~7k miles /10k km. I will not claim 100% that its not a possibility that the gasket is blown, but have yet to see any of the telltale symptoms that go along with it. Planning on doing twin turbo setup on it within the next 8-12mo, so regardless of state of it, either its fine, lasts until i pull motor to do turbos, or it fails, and i pull motor. either way im not too concerned as ive already bought a longblock with low mi/km as a backup. Sadly, the amount of labor involved in doing that rear gasket (on the presumption of paying someone else to do it), is quite a bit higher than simply swapping motors. So as is, im willing to roll the dice... im well aware of what Could happen... but with it passing all diagnostic tests... im not overly concerned. But I do appreciate you making light of it. I will make a note to run it through diagnostics with scanner next chance i get, but its not like im sitting at 5-8mpg.... i went from ~16-17, down to ~14.... which is really more telltale of, plugs need to be done, air filters changed, possible o2 sensor replacement as others have mentioned, n new MAF sensors probably wouldnt be the worst idea...

oakley1984

nah, rpm range is fine.... when an engine is regularly used beyond its in balance range, the signs are clear as day in the oil... there will be particulate, and fine metal particles that can be visibly seen in a smear test of the used oil. none of that is present. there is a large difference between pushing something beyond its limits and using something to its full potential. ive probably destroyed about 20 vehicles/drivetrains at this point... abuse shows... and shows quickly lol. biggest thing to take away from this is, Use GOOD oil, if youre really, Using the drivetrain to its potential, cut oil change intervals in half, DO NOT use fram oil filters. and most importantly, pay close attention to what the feedback from the vehicle is trying to tell you. I may be expeiriencing a slight decrease in fuel efficancy, but performance has not suffered, engine runs very smoothly, oil changes always come back clean. My opinion sides with those suggesting changing o2 sensors... as the only change ive seen in the last month or 2 is, exhaust smells a lil rich.

Baadnewsburr

iTrader: (3)

Sorry, my bad I think I was unclear.

I was speculating on driving in the rpm range of 4-7k for regular driving is killing the fuel efficiency, not referring to killing the engine...

Theres nothing wrong with working the powerband per se...I just don't expect good mileage from it....I've had my G for years now as a daily, and trust me I know, with good maintenance you can track it and push it hard regularly and it won't flinch...also, i'm pretty sure it benefits from being driving at WOT from time to time under the right conditions... but gas mileage wise, you can go through a full tank on these cars in a couple of hours on a track day working it through the band the whole time, which again is perfectly fine if the cars well maintained.