Use regular Dino 15W-40 and you will eliminate an oil viscosity issue. I use Chevron Delo and either I have two great engines with almost no blow-by or I am using a good oil.

Change the injectors all at one. If you really need to know which old one is bad, send them to me and I will pop test them for you. Just remember that if you have bad compression, injectors won't fix any of your problems.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge