Know of several that use filtered vegetable oil from resteraunt fryers. Start on diesel then switch to veggie oil then before shutting engine down switch back to diesel for a few minutes.
Dont know about yours but 2000 RPM is the magic number for mine, if I stay at or under I get around 18mpg on the highway whether towing or not maybe give that a try. With 3.73 ratio and 285/75R16s that gets me close to 70mph.
I just replaced the plug on my cord and routed out between hood and left headlight it's been that way for 4 years now without any more issues, and we use them quite often here in Alaska.
2000 F-350 I run rotella syn. and it gets kinda cold here in Alaska if I have access I plug in when temps. get below 20, but with the syn. oil it'll fire right up after sitting in -25 degree weather for 2 weeks. Cycle the glow plugs twice and go for it, let her warm for several minutes and go...
Here in Alaska I use Rotella 5w40 synthetic and dont have to plug in till it gets -25 Degrees. Sure is nice when I cant plug in and have been gone for 2 weeks at a time at sub zero weather to know the old girl(2000 F350) will fire right up. Wont do this with conventional oil.