2011 X5 35d Low MPG Issue

[Recon3D]

Hi guys,

I recently purchased a 2011 x5 35d and noticed that my average mpg has been kind of low. I've been averaging 21 mpg (according to the BC) with about 50/50 city/highway driving. I'm struggling to obtain 400 miles out of a tank.

I recently replaced the thermostat as that failed open, however, it didn't do a whole lot to my mpg. The thermostat now works properly and gets up to temp. I'm not sure if it's a clogged DPF, I've been monitoring my DPF with bimmer-tool and it appears that there's not that much ash/soot. I also checked my manifold for CBU, while there was a little cbu, it's nothing crazy. and I'm starting to think it might be related to my heavy 20" Style 168 wheel setup.

Any other ideas on what this could be potentially related to or does this seem normal to you guys?

[RL18]

Originally Posted by Recon3D

Hi guys,

I recently purchased a 2011 x5 35d and noticed that my average mpg has been kind of low. I've been averaging 21 mpg (according to the BC) with about 50/50 city/highway driving. I'm struggling to obtain 400 miles out of a tank.

I recently replaced the thermostat as that failed open, however, it didn't do a whole lot to my mpg. The thermostat now works properly and gets up to temp. I'm not sure if it's a clogged DPF, I've been monitoring my DPF with bimmer-tool and it appears that there's not that much ash/soot. I also checked my manifold for CBU, while there was a little cbu, it's nothing crazy. and I'm starting to think it might be related to my heavy 20" Style 168 wheel setup.

Any other ideas on what this could be potentially related to or does this seem normal to you guys?

I'm running 30.5" oversized tires on my x5d and still get 22-23mpg. Have you done vacuum lines yet?

[sunny_j]

Originally Posted by RL18

I'm running 30.5" oversized tires on my x5d and still get 22-23mpg. Have you done vacuum lines yet?

this. if thermostat is within operating spec next would be to refresh the 10 year old vacuum system. on the winter wheels i'm averaging 27mpg

[JDAURIA]

Like others have said. Thermostat would be first to check/replace and than vac lines

[Recon3D]

Originally Posted by JDNY516

Like others have said. Thermostat would be first to check/replace and than vac lines

Hmm, I have replaced the thermostat and it gets up to operating temperature now. I guess I'd have to go over the vacuum lines, they don't look anywhere near the shape of the ones in the video. Is there a way to detect a vacuum leak electronically or only using a smoke machine?