Poor fuel consumption X5 diesel

[514.X5]

Hi

I have been getting poor fuel consumption on my 2011 35d X5. it struggles to stay under 10L/100km. ı mostly do highway and cruise at 100km/h most of the time. I know she can do better than that sure.

-Replaced the thermostat that was staying open.
-Did a DPF delete and tune, I really thought that would help but was not noticeable.
-Did a carbon cleanup 2 weeks ago that eliminates carbon build on diesel/gas engines. No positive results.
-Air filter is clean.

What else could I check or what worked for you?

Thanks

[andrewwynn]

Have you measured the consumption at the pump or just relying on the obc dashboard numbers? The dash number is not always accurate and can be calibrated of it's off.

That said, diesel's often have a performance problem if their vaccum reservoir leaks. You can use a vacuum pump to test but real world test is climb a long hill under power. The turbo will give up if the vaccum is leaking.

First though, run though a good part of the tank fill up and measure and do the math.


–awr–

Using Tapatalk VIP on iPhone

[514.X5]

I usually rely on the dash board but also always reset my km counter when I fill up the tank. I get around 850 km on a full tank maybe 900 if i really stretch the limits. Thats ruffly 10L per 100km as the tank is about 83 liters more or less. That makes me think the dashboard is not off.

When you say the turbo will give up are you talking about limp mode? I know for a fact that if i push the engine aggressively and drive fast it gets into a mode where you can drive with a very restricted power output until the car has been shutoff and restarted.

Maybe the vacuum reservoir need to be checked?

[andrewwynn]

If you drive hard and it kicks in limp mode something is definitely wrong.

Yes definitely check the vacuum reservoir.

The typical symptom of the vacuum reservoir failing is you lose power going up a long hill.


–awr–

Using Tapatalk VIP on iPhone

[josiahg52]

I just drive it. 190k mikes now and still gets 6 - 8/100km. I've regularly used LiquiMoly diesel additives in the past but for the past couple of years I've been using Archoil diesel treatments.

Clogged DPF, poor fuel, bad fuel filter, cold ambient temperatures, short trips (especially in cold temperatures), excessive idling, stop and go driving.

How did you clean the carbon? It builds up on the top of the valves on DI engines. Cleaning it properly is relatively invasive procedure.

[Clavurion]

Have you checked the running temp with diagnostics or from cluster hidden menu? It should be 88-92 C.

[andrewwynn]

Solid query: when my tstar failed open I drove four months never getting to closed loop due to the moronic nay, asinine non thermometer on the dash.

I was wondering why my consumption went to shit before the shitty gas for winter kicked in.


–awr–

Using Tapatalk VIP on iPhone

[josiahg52]

88C+ is in normal ambient temperatures. In extreme cold winter temperatures, like in the deep negative teens and 20s, 80C will be a struggle. That alone will not crater consumption. I use a ScanGauge3 to monitor coolant and oil temperatures and it's been really cold in Maine, -15 to -25C in the mornings. My drive is 45 miles in the morning, some straight through town and then 55mph in the middle, then 45mph to the destination, still get 26+ mpg and coolant temperature gets to about 75C, 80C on slightly warmer days. I don't know, maybe intake or ambient temperature plays a larger role in fuel strategy than we surmise. It does increase in the warmer months to 28mpg+. Get it on the pure highway and it's high no matter what, 30mpg+.

[Clavurion]

Originally Posted by josiahg52

88F+ is in normal ambient temperatures. In extreme cold winter temperatures, like in single digits, 80F will be a struggle. That alone will not crater consumption. I use a ScanGauge3 to monitor coolant and oil temperatures and it's been really cold in Maine. My drive is 45 miles in the morning, some straight through town and then 55mph in the middle, then 45mph to the destination, still get 26+ mpg and coolant temperature gets to about 75F, 80F on slightly warmer days. I don't know, maybe intake or ambient temperature plays a larger role in fuel strategy than we surmise. It does increase in the warmer months to 28mpg+. Get it on the pure highway and it's high no matter what, 30mpg+.

Did you mean Celsius instead on Fahrenheit?

[josiahg52]

Celsius