Lucas does their homework. Lucas TB Zinc isn't going to eat the copper, aluminum, brass or bronze out of your engine or transmission. It's an extreme pressure additive. That alone would make it a bad idea to use it in the primary case housing your clutch. Your average car motor has plenty of exposed copper, aluminium, brass & bronze. AFAIK the only bronze in the 4-speed would be if you put H's bushes in there yourself, cheap steel seems to be the OEM preference, and in any event Lucas says it's a non-issue. At $12 - $20 per pint bottle it's unlikely you'll run it straight. The high zinc content means it's hostile to any catalytic converters it encounters, so keep it away from modern smog engines. Don't eat it, breathe it or get in your eyes - basic stuff.https://www.lucasoilcenter.com/shop/lucas-oil-products/problem-solvers-utility-lubricants/lucas-tb-zinc-plus-engine-break-in-oil-additive/TB Zinc-Plus Engine Break-In Additive | Problem Solvers & Utility Lubricants
Available in 16 ounce bottle [#10063], 16 ounce bottle case (12 per case) [#10063C], 55 gallon drum [#10472]
Lucas TB Zinc-Plus Engine Break-In Oil Additive is designed for all who fear the initial break-in period of any new motor, especially if running a flat tappet camshaft. It has an additive package that will help seat in the new rings while providing an excellent extreme pressure additive package that will help protect the entire valve train and camshaft. Dyno testing shows a more efficient and much faster with less blow by break-in when TB Zinc-Plus used. resulting in less engine run time prior to race day.
The TB Zinc-Plus is specially formulated with ZDDP to prevent camshaft and valve train wear in classic cars, hot rods and racing engines. It is also for use in any racing situation to increase your extreme pressure additives in any conventional or synthetic motor oil.
REMEMBER: Lucas Zinc Additive protects camshaft lifters and valve train during break-in period of motors. It is excellent for flat tappet camshafts during break-in or
as an additive to any motor oil to prevent premature wear. It contains an exclusive blend of extreme pressure additives and is designed for race applications requiring additional extreme pressure additives.https://lucasoil.com/faqhttps://lucasoil.com/products/engine-builder-lubricants/engine-break-in-oil-additive-tb-zinc-plusKEY BENEFITS
Protects camshaft lifters and valve train during break-in period of motor
Excellent for flat tappet camshafts during break-in or as an
additive to any motor oil to prevent premature wear
Exclusive blend of extreme pressure additives
Add one bottle with every oil change to increase the
zinc content of your motor oil
Designed for race applications requiring additional
extreme pressure additives
Dyno testing shows a more efficient break-in when used
resulting in less engine run time prior to race day
Not designed for passenger car use
https://lucasoil.com/pdf/TDS_Break-In-Additive.pdf(MSDS)
https://lucasoil.com/pdf/SDS_Engine-Break-In-Oil-TBZinc.pdf