https://www.f150online.com/forums/sh...d.php?t=104531

In the thread above, MACH1 notes that propane injection gets you 20mpg+. Is this mod worth the money and how much is the average gain from stock (whatever stock is, I thought it was about 20mpg highway stock.

 

Yes propane will get you increaed gas milage because it burns a little hotter and therefor makes all of the diesel burn, but just remember you will have to factor in the cost of the gallons of propane to see if it actually saves money...it will also add some power in the 50 hp range, and will keep your enigine cleaner. Most systems are in the $500 range...

 

You may get some slight increase in mpg, but don't plan on getting 20+. Thats very rare for a PSD no matter the mods to be doing that well. You need to do ALOT more research before you start throwing propane at something. Take about a week and search the archives at TDS. Read all the threads where propane has vented blocks and in general destroyed engines. BECAUSE its so volitile you really need to know what you're doing or it'll bite you hard. Its imperative that you have a chip that can control it. The timing needs to be backed way off or else detonation will occur which will kill an engine in short order. If you have an 01 and newer your chances of catastrophic meltdown is much higher due to the connecting rod construction. The other thing to keep in mind, propane will void your warranty so fast it'll make your head spin. This has been one thing that no matter what dealer sees it (unlike chips that some will overlook) your warranty will be gone, due to the instability of the system. It CAN be run safely, you need to know how to control it and how it works. Even with the stronger connecting rods I didn't want to run it on mine due to throwing a rod or blowing a head gasket. Stick with straight #2 and the power you make will be much more durable.