Just got done reading the other thread and came back to see you summarized, thanks, good call on viscosity for ease of starting too
By doing this method you save the canister filters from catching dislodged junk it sounds like, but also doesn't clean pump, feed or return lines.
Mine has sat for a while *cough* years, so wonder if that also helps simplify the equation while trying to start it again by cutting out the rest of the fuel system.
If the lines are that bad, it's easier/cheaper to replace them.
Motor oil and ATF have a TON of detergents. It will get a lot of stuff, but won't really touch 60+ years of varnish, gunk, and rust, that is in the tank of most deuces these days.
Keep in mind that you can dislodge stuff that can clog things you don't want to clog. It's a risk you take. That's why it's safer to only do a purge with fuel supply line and return line disconnected with an inline filter being used. It continuously runs all the cleaner through, multiple times, with filter grabbing the gunk it pulls off, while simultaneously pushing what it's using through the injectors, cleaning them as well.
Assuming you don't want to replace the fuel line....
I'd first get spin on filters and install them, because you're gonna kill your fuel filters pretty quick if you try and do a whole system purge.
I'd get some fresh (high mileage) oil and high mileage ATF, both which have extra detergent additives.... a couple gallons minimum. I'd dump an entire large bottle of diesel kleen in there (the one that treats 250 gallons) or at the very least, 1 medium size bottle that treats 100 gallons. AT LEAST a gallon of TCW3, a gallon of MMO, and a couple bottles of seafoam/B12.
The oils (and ATF) will provide detergents and dispersants, the TCw3 provides lubricity, the MMO and seafoam are cleaners (with seafoam being a little harsher), and while it's not a miracle cure, it'll pretty much get it as clean as it can get, safely, before you have to take more drastic steps like pulling the tank off and cleaning it.
You're going to spend a good $150 on the above cocktail.
Also note, that's a 'diesel safe' cocktail... That nearly all but the newest diesels can run without issue. The multifuel engine may be able to handle higher quantities of harsher cleaners (like B12), since it contains more powerful solvents that are more readily combustible, more designed for gasoline engines. But, given the age of things, I wouldn't, as it's a much drier product, and you run the risk of not getting adequate lubrication or messing up seals. Another issue, as mentioned, is if it works TOO good, then you have filter screens clogged, and gunk that was stuck on the bottom of the tank, now clogging your filters every 100 miles.
When I first started out on running motor oil, I only got about 100 miles before filter was clogged, as it was cleaning everything out. Each tank after that I'd get longer and longer between needing to replace filters, but I wanna say I went through 3 sets of filters within 1K miles.... because of how well the oil cleaned everything out. Yes, filters so clogged that it was starving the engine of fuel.
