Hate to trade my truck with C15 but got a big Mpg education this week with a Volvo

If Justin is the one that I have talked to (I think he is) he does seem to know his stuff pretty good.

You have soot around the number one cylinder, between the exhaust manifold and the head, or the expansion joint? Any leak at all is not good, if you are leaking there you are loosing efficiency. I hate when shops tell people that stuff like this doesn't matter, because it does.

A common problem with the manifold is that the studs can break off, are all of your studs intact with the nuts on them, as well as the studs for both turbos?

CAC, and all the piping from hot side to cold side, none of this should be leaking, at all. I know OEM's say that a certain percentage is ok, but I don't believe it, any leak at all here is also loosing efficiency.

Another common problem that I think gets overlooked is the bellows, or expansion joints. These are the stainless accordion looking pieces that go between the turbos, there are two of those, and one longer one that goes to the pre-cooler. If there are any cracks in them, they need to be replaced. If one of them is cracked, why is it cracked? The common reason is that it is no longer in alignment. If you have one that is cracked I can post pictures of mine, and explain how to align it. Sometimes they crack just from all the heat and cool cycles that they go thru, as well as the vibration and expansion and contraction.

 

another one to look at is the asbestos ring that goes in the accordion pipe that goes to the precooler. it will leak from the expansion and cooling of the tube. it is overlooked a lot. you can idle up to about 1700 to make a couple of pounds of boost then squirt windex or soapy water on all the conections any bubbles and you have found a leak.

 

Check your fuel system also. Put a gauge i the line and get your pressure up to 100lbs by shimming the pump spring or replacing it with the factory high pressure spring kit. Put a sight glass in the fuel filter head after the filter head and if you have air replace the filter head with a Cummins 120gph head. The stock CAT head is restrictive when new even before they crack and suck air. Use Fleetguard FS1000 filter for better flow also. The ACERT requires high fuel flow yet is sold with low flow parts, goofy to me. "Twin turbos" are nearly always better than singles in normal driving applications.

Bullydog will get you the right tune, just stay after them. You have the perfect gearing for an ACERT if you have lo pro 22.5s - 65mph = 1325rpm.

Then there's driving habits and idle time which account for most of the savings or loss and tire rolling resistance... Bottom line is that you can easily get your 6.5 from your truck.

 

Oscar is correct ANY leak is too much

 

A friend of mine got one of this Pete ex Werner truck, 06 ,is killing him on fuel.
6.4 is not bad , but I know guys doing way better with D12.
I'm getting 8-9+ with Volvo D13 /2008 since I got the truck in July 2007. I spent some $$ in emissions maintenance but this motor is amazing on fuel and still pulling great with 1,173,000 miles on original motor.

 

Get it up to a higher RPM somewhere closer to 1500. My dad has the 9900IX and he gets 6 or better.