Don't use it neat - it doesn't have any lubricity, so it'll cause massive wear in your injector pump in short order. However, mixed with diesel (not sure of the proportions, but I'd have thought 50:50 should be plenty), it will work fine.
I'm not sure if diesel & heating oil are properly miscible, so it may be that they separate into layers over time (an experiment in a jam-jar will prove the concept; if you get distinct layers forming, they're not miscible). In that case, it'll still work, but you'd want to mix small batches of fuel at a time, rather than just treating a whole barrel. In that case, it may also be worth setting up a valve so you can switch to diesel for startup/shutdown.