what have you guys done to become more fuel efficient

Not a chance, I only use it in emergencies

 

What kind of fuel mileage are you getting? My c15's seem to do the best about 13 to 1350 rpms around 62 mph. You might try that for a while and see if it comes up a little.

 

you guys are coasting down hills to save fuel, you got to be kidding.

 

using the jake will use more fuel than not. That being said, the jake is a safety issue when going down steep grades and safety always trumps mpg. When coasting down hill, I will hit the jake to slow me down a bit, then turn it off, then hit it again and so on, as needed. I'm not sure about the cat engine, but the cummins isx will actually shut off the fuel pump when you are coasting in gear so you are using 0 fuel. If you're coasting in neutral, it will use more fuel than coasting in gear. Basically, use the jake only when needed. If you don't need it, just let it coast in gear.

 

The easiest way to save fuel is slow down.Learn to watch your boost gauge, and drive conservatively. Several years ago I made an effort to run smarter, and it is paying off in several ways. By slowing down, not only do I get better fuel mileage, but brakes last longer, less wear and tear on the engine, MUCH better tire wear, fewer moments of terror when something suddenly appears in your lane, lower insurance rates by fewer tickets, and less tired at the end of the day.The other ideas about tire pressure, well tuned engine,reducing idling, etc., will all pay off nicely too. I know sometimes you gotta go hard,but do you really need to always keep your foot in it ?
It takes a little work to learn to slow down, but it sure is a good thing to do.Puts $$$$ in my bank.

 

when you say coasting down hills do you mean coasting out of gear?

 

I think 6 is pretty good for in town, not bad.

 

No, that's illegal. Always coast in gear.