What are some repairs and upgrades that can improve mpg?

Sorry we can't talk about modifying emission equipment on here or I'd say get a tune.

 

Change your air filter

 

Is this for real & is that why some of the technical discussions have been removed?

 

tire pressure, good air filter. proper alignment, overhead if it hasn't been done. injector flush. turbo check that it's spinning max rpms. CAC for leaks. high flow muffler.

haul light loads and stay in the middle of the country. (unrealistically speaking)

and if your pulling van, adjust your 5th wheel to the front so that your steers weight 12,200 with full tanks of fuel. keep the gap to a minimum between truck and trailer. you really don't need to drive lighter steers. so, the only weight you'll have to worry about is the trailer.

 

Synthetic oils will help fuel economy.
Super single tires helps.
If your pulling open deck/flat or step, remove any upper wind dams or wings.

The biggest thing for fuel economy is cut your speed down.

How about quit pulling a trailer, just bobtail around. LOL

 

get lighter load. Put some undertray fairings on the trailer.

 

Lift axles help also.

How about propane injection. I've heard that will incease fuel economoy a bunch. I'd like to try that some day.

 

Propane for fuel economy? Never heard that, I do know that it will give a big boost to power. Only for a short period though cause the propane can overheat/burnup your motor. Not to mention what it would probably do to all the sensors and computers in these modern motors or modern anti-emission choked exhaust systems

 

Maybe your thinking of Ethenol, not propane. There is a few different threads on here about it.
Propane injection at approx. 3-5% cause the diesel to burn more throughly, actually cleans up the emmissions greatly.