Flying a twin with one engine at idle  

Performance  I have a ferry flight coming up in a Bell Medium and am having some fuel issues. I fuel out of barrels and I have a 320 nm leg tomorrow. Have any of you found if you go to idle with one engine and 100% (or so maybe a touch less) on the other, it saves you some quantifiable fuel? Looking for experienced pilots to help me out. 

"Bell medium" as in 212/412 or a 222/230? Those old engines ain't economical in idle. The RFM is your friend in this case- performance charts especially. Been decades since I had to calculate this, but here goes:

I'd copy and magnify the chart to do this (on paper in them old days)

RFM power chart, big bulge.

From the lower left, a line on a tangent to the power curve is your best shot, should give you a ground speed or power setting.

And you have to factor in the atmospherics, winds especially.

I'm a nervous sort but I'm also an old fart. I would go a long way around to have a comfortable fuel stop(s) on any leg...