I've just had one fitted, I can't say I notice a difference in throttle response or how the car revs/idles, driving feels a little smoother maybe, but one thing is for sure my fuel gauge needle hasn't moved since I filled up after fitting.

Is a substantial improvement in MPG standard for this mod?

 

Yes even more so than an ARB

 

Crikey at 1-2 MPG extra the ARB was small fry.

I can't even commit to a figure yet for the crank pulley as the gauge literally hasn't moved.

 

mabey gauge is broke lol i struggle to see 150 miles from full tank
should get me sum pulleys me thinks lol

 

Nah, the gauge still goes up when I drive uphill and down when I go downhill.

They say a lightweight crank is like taking 100lbs of weight off the car but in all honesty my car's mpg doesn't go up when my 126lb wife isn't in the car. Maybe the drop in revs needed in all loads is improving the MPG noticeably?

Car is like a friggin Derv. Even the back bumper is black.