STX550 Fuel consumption

[mannix]

Anyone got high fuel consumption problems with their STX550?
I am totally dissatisfied with the fuel economy of our STX550. I have reported this on several occasions to the servicing dealer when the vehicle has been in for a service. The service people advised the fuel pump had been through a “relearn’ process. There was no noticeable difference. When I was in Queensland I had a dealer service the vehicle and asked if he could check the fuel pump for the “relearn” process as the fuel economy is poor. He advised that there is no such process for the STX550 fuel pump, so I am confused as to who is right, nevertheless the fuel usage is lousy. When towing the fuel usage can average high as 25 litres per 100 Kilometres. Towing the same caravan with 3 litre BMW fuel usage can average high as 15 litres per 100 Kilometres but is generally between 12 & 14 litres per 100 Kilometres and with a 3 litre Patrol fuel usage can average high as 14 litres per 100 Kilometres but is generally around 12 litres per 100 Kilometres. As I live in the country most of the driving is Highway environment as opposed to city stop start driving so I would expect to see fuel usage equal to or better that the proclaimed 9.3 litres per 100 Kilometres combined highway city cycle, but is generally between 12.8 and 15.4 per 100 Kilometres. A noticeable defect is the extraordinary amount of black and light blue/grey exhaust smoke emitted when the vehicle is first started and when accelerating or under load. Paul Glover, the motor writer, has stated that there are some sensors on the STX550 that can fail causing excessive fuel use. The service people take the vehicle for a 25 kilometre cruse up the freeway and advise that the fuel usage is within “Nissans average fuel usage for this vehicle”. Indeed 3 out of 5 times I can get 9.8, 10.1 and 9.9 per 100 Kilometres but over the life of a tank it does not make it. Any ideas?

 

[BJJ84]

definitely sounds high to me mate, especially for mainly highway driving. a mate has a V9X STX and the trip computer says around 8ish i think on highway trips.

can't give musch insight into a solution, but perhaps try an OBD reader and the torque app to see for yourself what the ECU is saying

 

[KraftyPg]

Unfortunately if the car falls into the 'average' usage figures they have there is very little they can or will want to do, it sucks but when the figures are a guide only and there is no magic figure a car must attain it's hard even for experts to change much and stay within the bounds of their knowledge/job title.

Have you confirmed the car figures with actual figures, there has been plenty of reports about all manufacturers having faulty gauges and read outs, it's the first and easiest check you can make.

If you can get 10ish '3 out of 5 times' what are you doing in those times that may be different, i.e more up hill, more wind etc. There is hundreds of things that can effect the figures but if you can attain the figures at one time and not another looking at the good times may be a key to helping.

The figures do sound high and I've not seen any signs of black smoke from the old mans 550 and he's only reached 14/100 towing the 5m tinnie through the hills.

If I was you I'd try Nissan again (even if you have to try another dealer) and see if they can confirm or deny PG's story. Chances are if he said it came from Nissan head office not necessarily a technical person because the guy only quotes what others have told him. He's about as bias as Roothy and he's got very little idea about these things himself (the guy still suggests to callers on the radio that all Nav's are the same). If his story can be confirmed ask your dealer what they can or will do about it.

 

[BJJ84]

if you are getting blue smoke from the exhaust, i'd be very concerned. blue can only be burning oil, so i'd be taking it straight back

 

[Adam777]

Sounds high to me too, i drove to noosa and reset the trip and economy settings before i set off and got 7.4 litres per 100, around town it uses around 8.8 - 9.1 litres but like i say this is short start stops and if i tow around 1.2 tonnes it returns mid to high 10's having said all this i am easy on the truck and don't hammer it.

I do know of a bloke who has the V6 engine in an STX and he said he thought his smoked a lot and took it to a diesel mechanic who found water in the fuel and asked him where he filled up and advised only to use caltex or BP ultimate fuel in it, don't know if that is a factor.

I once had a Golf tdi that had really excessive fuel usage and smoked like you wouldn't believe and that turned out to be the air mass meter so perhaps a sensor isn't out of the question.

 

[V9x]

That doesnt sound too bad to me mate .25L per 100 is excessive though. Mine was doing low 10s on highway driving with no load , then upto about 14ish with little jetski trailer behind. now that I'm running 275/70/17 on the car it's doing around the 12 mark unloaded highway driving. I haven't towed anything yet or had it loaded up since the tyre change though so can't give you any figures on that. How many kilometers has yours done ? Tyre size? Van weight?

 

[Adam777]

It amazes me how much the fuel consumption on these vehicles varies, mine is totally stock & i can understand other peoples being more thirsty with bigger treaded tyres on but there seems to be heaps of difference just vehicle to vehicle i know we all drive differently etc & in different conditions but even so theres big variations. Wonder how much big cow catcher front bumpers & spotties affect the fuel consumption as it has got to interfere with what little aerodynamics these vehicles all ready have never mind the extra weight.

How kind was everyone else to their V6's in the early days of their lives as i was really gentle on mine till it hit around the 3000 k's mark, but even now i would say mine has a really easy life. I haven't turned the aircon off since day one so i don't know how that would affect fuel usage pretty minimal i would think as they don't sap the same power as they used to.

 

[KraftyPg]

Given that all aerodynamic tests would have been done on a stock car (on a computer) you can bet when they designed the car they did as many tests as they could to make such a brick like shape as aerodynamic as possible and the bits they added were added to take advantage of that or make it better. Adding anything to the outside of the vehicle will change those aerodynamics, it has to, but the effects will always be different and that's one of the main reasons that pin pointing differences between two cars is so difficult and why no manufacturer will ever give an exact figure to aim for and instead opt for using an 'average' figure.

 

[Adam777]

Yeah i agree with you there, you only have to look at how they moulded the front bumper into the wings etc to know that the designers were trying to make the front of this thing as slippery as possible, i'm actually really happy with the consumption on mine as for such a big heavy item with the aerodynamics similar to those of the side of a house i reckon they don't do too bad. Fold your mirrors in and you would probably drop a litre per hundred k's!

 

[V9x]

Mine has a bar and Spotties , snorkel ect but mine still has better fuel consumption than the bloke I work with who has the same vehicle as me. He does alot of towing cool rooms mostly and his fuel figures would be around the ones you have stated mannix, he has no bar ,snorkel ,or gear ect . Strange how there is such a difference between vehicles. EGR valve can effect fuel usage and smoking ect can't it?

 

[KraftyPg]

A few years ago it was KC owners complaining that they were getting 15's and higher where most DC's of the time were getting 10-12's. Still to this day I don't think there has been a viable reason as to why two such similar but different vehicles got the figures they did and Nissan didn't want to know about it. But since then they seem to have done something to the KC's because the owners are reporting much closer figures to those obtained by DC owners.

If it was only Nissan that was not interested in addressing fuel usage difference between similar models there would be grounds for owners to push them harder but all manufactures have chosen to take the same stance these days.

 

[Adam777]

Surely yours having the 2" body lift too would make your figures worse than a vehicle with the standard ride height, so strange the big variations.

 

[V9x]

Surely yours having the 2" body lift too would make your figures worse than a vehicle with the standard ride height, so strange the big variations.

I never thought of this mate. But I would agree that it would have an adverse effect on my vehicle vs standard in the fuel economy department

 

[Adam777]

Didn't myth busters ages ago do a test with a ute to see if the fuel consumption was different with a tonneau cover fitted as opposed to not having one fitted, also just having the tailgate down affected it too from what i remember. They also proved that riding round with your window down as an alternative to having your aircon on used more fuel also.

 

[KraftyPg]

Mythbusters should be taken with several grains of salt and like most of what they do there was more than enough anomalies to kill any real accuracy in their tests, they are good entertainment but that's about it.

 

[LLadnar]

Mine usually runs at around the 9.8 - 10.2 ltr/min.
It does get up to the 12's when I spend a lot of time in Newcastle or when I'm towing the van or trailer.

 

[BMGTZ]

on the freeway at 80-100k mine is saying 8.8 as average. driven around the suburbs and given a boot full occasionally 11.3

I have no towing figures yet ...will do in two weeks.

 

[Busiboy]

Mine sits at 12 around town but I do real slow stop start stuff, highway towing 13-15

Mine feels high for the around town figures despite my site driving

 

[ozsnow]

I just completed a trip from Jindabyne to Sydney and return. Driving to Sydney empty the vehicle returned high 9's. Travelling back with about 1.8 tonnes of boat, A/C running and a pretty strong headwind it was getting mid 17's. Mind you I was not taking it easy running at 110 on the freeway and the 100 on the Monaro hwy.

It certainly makes a great tow vehicle.

General running around the mountains it is returning about 11.

 

[Old.Tony]

To the OP - you might consider getting your car checked for the EGR recall, excessive EGR causes black smoke and performance loss (which returns as poor economy to achieve expected performance).

There most definitely IS a relearn procedure, but it's not something that Nissan do - the car does it itself. Here's how it works.

You (or Nissan) resets the ECU so that the fuel map is lost (the car learns your driving habits and adjusts the fuel input accordingly). When you next start driving, the car learns again how you drive. It's no more complicated than that.

The easiest reset procedure that won't cause problems with the car is as follows:

1) Write down the trip meter values if you use them to record fuel economy
2) Pop the bonnet
3) Disconnect the battery
4) Go inside the cabin and put your foot on the brake pedal, count to 10
5) Reconnect the battery, close bonnet