I noticed the opposite results on a 3500 mile trip recently...lost about 2 MPG on biodiesel as opposed to number 2 diesel...Have a 2007 Journey with 300 Cummins. Some places had both kinds available and others on the west coast only had biodiesel...by the way, the roads in California are really rough while the roads in Oregon are much better...just my observation. I don't think biodiesel will hurt any older diesel engines but I don't think it will give more power or MPG...Buford.
As long as you are running anything up to B20 (20% biodiesel/80% petroleum), you should be OK. I've been running B100 (pure biodiesel) in my John Deere 670 for over 20 years (since before it was cool). After maybe 10 years, it turned the natural rubber hoses to goo. I switched to urethane hoses, which lasted a few years and then crumbled. Now I'm onto Viton hoses, I think.
I read somewhere yesterday that early days bio-diesel also ate internal parts, like fuel pump guts and other parts, or at least caused them to fail prematurely. They say the current stuff "cleans" up fuel systems, but I have no substantive references of that suggestion. A lot of the internet based bio-diesel info seems to be hearsay mixed with some anecdotal experiences. I still try to avoid it when possible.