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expat1 Profile
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Date Registered: 04-2014
TOTAL POSTS: 19
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Bad fuel economy


I have already visited the fuel economy area of this forum.
Ok, heres the deal; my exy is drinking gas like a fish drinks water. I have tracked every fill-up on my android FuelLog app since April 28:
Worst 12.87 MPG (18.27L/ 100km)
AVG 15.99 MPG (14.71L/ 100km)
Best 24.44 MPG (9.62L/100km)

Highway driving gives me the best fuel economy... unfortunately I don't do much of that. I live in a city that is 90F (27C) annual average temperature, so the A/C is always on. I avoid the "stop and go" downtown city traffic, so its around a .5 to 2km stretch between stoplights. 95% of my driving is in the city, so I'm getting from 15L to 18L per 100km. This is killing me, cost of fuel per month would pay the monthly payment on a brand new car.

Failed attempts to improve fuel economy:
  Nissan OEM spark plugs
  ECU reset (unhooked battery for 24 hours)
  Bosch oxygen sensor
  Nissan air filter
  cleaned intake housing and tube
  Cleaned Mass Airflow Sensor
  street tires, balance and alignment (non all-terrain tires, don't know the exact term)
  Coolant flush

On the "To Do" list
  Throttle body cleaning ( I have idle relearn procedures from this forum).
  Butterfly valve inspection and loctite
  Auto trans filter/ fluid change to Nissan OEM fluid
  MAF cleaning (again)
  Find who the F*#k sells Sea Foam in this country

Vehicle info
x-trail T30 2005, QR25DE 2.5L Gasoline, Automatic trans. 149,000km. 20W-50 Shell helix X5. I use super unleaded gas (the best I can get here). no roof rack. it has the ridiculous spoiler on the back, and a short chrome bumper guard on the front.

Im thinking the next step is new fuel injectors and an aftermarket fuel filter in the engine bay.


Any thoughts/ comments would be greatly appreciated. I don't want to keep sinking cash into this thing with zero results.

Last edited by expat1, 25/Aug/2014, 3:16 pm
25/Aug/2014, 2:57 pm Link to this post Send Email PM   Send Private Message Blog
 
jalalski Profile
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Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29094
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Re:


Thread moved to the forum section it belongs to.

Have you replaced the CAM and Crank sensors at all? if not, this should be your next step of the trouble-shooting.

Last edited by jalalski, 26/Aug/2014, 6:58 am


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26/Aug/2014, 6:57 am Link to this post Send Private Message MSN Blog
 
expat1 Profile
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Date Registered: 04-2014
TOTAL POSTS: 19
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posticon Re: Re:


Hi Jalalski,
Yes, the cam and crank sensors have been replaced... I'm not exactly sure when because I found the old ones in the exy after I bought it. I'm thinking within the last 24 months.

Maybe a fuel injector cleaning is in order. the gasoline here is junk.

I'm also going to clean all the electrical grounding points as per some posts I found on this forum.

And maybe a new fuel cap.

And maybe I will just set it on fire...



27/Aug/2014, 3:05 pm Link to this post Send Email PM   Send Private Message Blog
 
DogTrail Profile
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X-TRAIL FANATIC
 


Date Registered: 05-2012
Location: Sunshine Coast
TOTAL POSTS: 481
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Re: Re:


Maybe it is the oil.

With mine, running the 10W/30 Caltex Magnatec super duper something (whatever the Dealer who must honour the warranty gives me), the much abused instant readout doesn't really drop much below '8' until I've covered at least 10Km, preferably 15 km to get all the oils & gears up to optimal running temperature.

When up to temperature, the instant readout drops to about 4-5 over the same level road.

I use A/C all summer but it seems to make little difference to my overall fuel consumption as I suspect the torquey 2.5L Donkey doesn't even notice it is there when the A/C is switched on.

Maybe a different oil would help lower the internal friction and improve the fuel economy for you?

I'm the first to admit that I know little on the subject but to me, your oil seems a bit thick at 20W50 for that environment which seems similar to mine.

Note: Though I average in the 8's, mine still sucks fuel in city traffic if I boot it between lights and on hills. That is to be expected

The greatest offender for poor fuel economy is stop-start traffic powered by a strong right foot....I find that drifting between the traffic lights & trying to match their sequence helps keep the frustration and fuel consumption downemoticon



Last edited by DogTrail, 2/Sep/2014, 6:58 pm


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2011/12 Australia:- 2.5 litre petrol 4WD, Series IV ST, CVT : + some gadgets and cosmetic add-on's. Dirt, (it protects the paintwork) X-2429(c).
2/Sep/2014, 6:21 pm Link to this post Send Email PM   Send Private Message
 
expat1 Profile
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Date Registered: 04-2014
TOTAL POSTS: 19
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Re: Re:


Thanks DogTrail, I'm due for an oil change so I think a lighter oil is in order. The owners manual lists 20W50 as usable for my environment, but optimum is 10W30 I think. My wife usually drives the Exy, and she thinks its a Ferrari (which might explain the consumption).
3/Sep/2014, 1:02 am Link to this post Send Email PM   Send Private Message Blog
 
Exywarrior Profile
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X-TRAIL FANATIC
 


Date Registered: 10-2011
Location: Darwin, NT
TOTAL POSTS: 325
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Re:


I read that you've cleaned your MAF sensor a couple of times, but I'd be starting to wonder if it is actually malfunctioning and needs replacement. A completely inoperable MAF would have a murderous effect on fuel economy.

MAFs are apparently rather delicate and easy to break. They're apparently not cheap but I'd be looking at replacing the MAF sensor completely as part of the faultfinding process.

Last edited by Exywarrior, 13/Dec/2014, 10:44 am


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Mark T
2011 Series 4 T31 TL Auto - Twilight, factory towbar, factory mats, tinting, Cooper CS5s, cathodic protection, paint protection, yada yada...and no Provent
X-2099
13/Dec/2014, 10:43 am Link to this post Send Email PM   Send Private Message Blog
 
Charlie250 Profile
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X-TRAIL ENTHUSIAST
 


Date Registered: 08-2012
TOTAL POSTS: 193
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Re: Fuel Economy


Without knowing your exact location/topography it's hard to fully understand or interpret your economy figures.

The QR25DE in the T30 is not a super economical engine.

Roof bars are of little consequence as they have a barely detectable level of wind drag.

People in inner city Sydney and Brisbane get similar economy figures to yourself.

The fact that you have been able to achieve 9.62lt/100km at some point, suggests that there's nothing wrong with the engine and that it's the stop start city driving environment.

As far as oil is concerned, Castrol Magnatec Professional 5W40 exceeds manufacturer specs and is what I have used for many years in my ute. It only comes in 20lt or 209lt drum. Castrol part number for the 20lt is 3350465



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X-2634 2012 Series IV TS Man, Kings Springs, Bridgestone D697's, High Tech Exhaust, Turbo Timer, DBA Slotted Rotors, QFM HPX Pads, Tow Bar, Cargo Barrier, UHF, HID Dr Lights, LED Light Bar, K&N Filter, Bonnet Struts, & Premium Tint
13/Dec/2014, 11:39 am Link to this post Send Email PM   Send Private Message Blog
 
expat1 Profile
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Date Registered: 04-2014
TOTAL POSTS: 19
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Re: Fuel Economy


Thanks Charlie250, on the HWY I'm getting 9.5/100km but im usually city driving. I just had the AC repaired and I disconnected the heater core also, which really helped the cabin temperature. I have since ran a bottle of SeaFoam through the engine and changed the tranny fluid, and have yet to calculate L/100km. I will keep everyone posted on the progress, which so far has been an exercise in futility.
14/Dec/2014, 9:55 am Link to this post Send Email PM   Send Private Message Blog
 
expat1 Profile
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Date Registered: 04-2014
TOTAL POSTS: 19
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Re: Re:


Thanks ExyWarrior, my exy isn't throwing check engine light for a malfunctioning MAF. I used CRC MAF cleaner to clean it, it didn't look dirty though, but it did run better after the cleaning.
15/Dec/2014, 7:35 am Link to this post Send Email PM   Send Private Message Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 6003
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Re: Re:


quote:

expat1 wrote:

Thanks ExyWarrior, my exy isn't throwing check engine light for a malfunctioning MAF. I used CRC MAF cleaner to clean it, it didn't look dirty though, but it did run better after the cleaning.



Though your initial post was detailed, you didn't mention that the check engine light was appearing. This would have alerted everyone that something needed checking and we could have directed you to the procedure to find the fault code yourself to help diagnose the problem sooner.

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Kev X450(c) T30 Guru
03 Titanium Ti T30 Series 1 **MODIFIED**
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23/Dec/2014, 8:22 am Link to this post Send Email PM   Send Private Message Blog
 


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