Additives + Cleaners

Additives + Cleaners

Every Fluid. Every Fix. No Guesswork.

Whether you're running a diesel workhorse or a gas-powered daily driver, what's moving through your fuel system, engine, and brakes matters just as much as the parts bolted to them. This collection covers fuel treatments, oil protection, DEF care, and brake fluid & cleaner for both platforms — Doc's Diesel and Doc's Auto Parts formulas, plus co-branded treatments built with Hot Shot's Secret.

What's In This Collection

Diesel fuel treatments that boost cetane, clean injectors, and restore lubricity lost in today's ultra-low sulfur diesel — plus a Gas System Treatment for the gas side of the shop. Oil Friction Treatment cuts metal-on-metal wear under heavy load and towing, diesel or gas. DEF Guard and DEF fluid keep your SCR system free of crystallization and fault codes. SOS Cold Weather Rescue and Winter Treatment anti-gel get you moving again when temps drop and fuel gels. And on the cleaning side, non-chlorinated brake parts cleaner and DOT 3 brake fluid keep your braking system firing on clean, dry fluid — no matter what's under the hood.

When To Use Them

Above all recommendations, follow your vehicle's manufacturer warranty guidelines.

24/7 Diesel Treatment + Cetane Boost: every fill-up
Interval Diesel Treatment: every 5,000 miles or at every fuel filter change
Oil Friction Treatment: every oil change
DEF Guard Additive: every DEF fill-up
DPF & Injector Fuel Flush: every 3rd tank, as a corrective treatment
SOS Cold Weather Rescue / Winter Treatment: as needed when temps drop and fuel gels
Gas System Treatment: per label directions
Brake Fluid: check reservoir every 2,000 miles
Brake Parts Cleaner: at every brake service

Built to OEM Specs. Backed by the Doc's Fitment Guarantee. No guesswork. No BS.

Free shipping on qualifying orders. Grab what your rig needs and get back to work.