I recommend what I do yearly on our vehicles, prior to the 25m ARX run (where the usual synth is substituted for dino during wash & rinse phases):
Pull the sparkplugs (on an engine thats been run a good 30-miles or more, with some WOT blasts), put 2-3 ozs LC20 in each cylinder. After one hour, rotate engine but one full turn, no more.
Top off each cylinder. Be sure LC20 added to meet or exceed 4-oz per quart oil capacity.
Next morning, cover cylinder bank with old bath towels, spin over engine several times to get any LC that has not made it past rings out of engine.
In well-ventilated area (street versus drive) re-install old plugs, start vehicle, let idle 10-minutes or until coolant fully-warmed. (Smoky).
Take car for easy run, allowing a decent warm-up of other components, and take some WOT blasts from about 30-50 mph. (West Nile Virus Mosquito fogger).
I then ease along to the local freeway and run home along it; a route that carries me about 15-miles, start to finish. (Everone is waiting for your engine to seize. I wave and smile, sometimes stand on it again.)
Do an oil/filter change, and install new spark plugs.
This is what we used to do on cars back in the days of points ignition and carbon build-up that today would be considered excessive. Only we used GUNK or MMO or some other solvent that one NEVER WOULD ATTEMPT TO DRIVE CAR!!!! Only allow it to idle on the high step of the choke (usually 15-1800 rpm, sometimes higher), NEVER putting a load on the engine.
And then change oil/filter again at 500 miles. And again at 2000-3000. No telling -- on a less-well-maintained vehicle -- what trash might come loose in engine.
I also, on a car with unknown history, but some detective work, would also run a butyl-cellosolve cleaner through if it looked as though coolant had ever gotten into oil. Or, a Chev small-block, when the fuel pump failed and the oil system was filled with gasoline (thus, water).
Stick with the winners, don't reinvent the wheel.
I have no experience with NEUTRA, but am a real LUBE CONTROL fan. It's cheap, it has a jillion uses, and it works as advertised.