One bottle of NüDef treats up to 25 gallons of DEF. Each dose treats 2.5 gallons, so you add one dose (roughly 10ml) per 2.5 gallons of DEF at every fill-up. For a standard 8-gallon pickup truck DEF tank, that is just over three doses per full tank. This guide covers the exact NüDef dosing ratio for every common diesel application, from pickup trucks to semi trucks, RVs, generators, and bulk DEF storage tanks.
NüDef Dosing Ratio
NüDef is formulated at a treat rate of one dose per 2.5 gallons of DEF. Each bottle contains 10 doses (8.45 fl oz / 250ml total), which means one bottle treats up to 25 gallons of DEF. The dosing is designed to work with any ISO 22241 compliant diesel exhaust fluid, regardless of brand.
You do not need to measure precisely to the milliliter. The dosing is generous enough that adding slightly more or less per fill has no negative consequence. The important thing is consistency. Treating at every fill rather than skipping and catching up later maintains continuous crystallization protection throughout the DEF system. NüDef is the only additive for DEF fluid that is single-purpose engineered for DEF stabilization, so every drop of the formula goes toward preventing crystallization rather than treating unrelated systems.
Dosing by Vehicle Type
Light-duty pickup trucks (Ford F-250/F-350, Ram 2500/3500, GMC Sierra HD, Chevy Silverado HD). Most diesel pickup trucks have DEF tanks ranging from 5 to 9 gallons. A typical fill adds 3 to 7 gallons of DEF. For a 5-gallon fill, add 2 doses of NüDef. For a 7-gallon fill, add 3 doses. One bottle of NüDef covers approximately 8 to 12 typical DEF fill-ups on a pickup truck, roughly a full driving year for many owners.
Heavy-duty semi trucks and commercial vehicles. Class 8 trucks typically carry 30 to 50 gallons of DEF. A full fill from empty requires 12 to 20 doses of NüDef. For fleet fueling operations, the most efficient approach is treating the bulk DEF storage tank directly at the fueling island at the correct treat ratio, so every vehicle that fuels receives treated DEF automatically.
Motorhomes and RVs. Diesel motorhomes typically have DEF tanks ranging from 10 to 20 gallons. A full fill requires 4 to 8 doses of NüDef. RV owners should also treat before seasonal storage. Add NüDef at the standard dose before parking, then run the engine 10 minutes to circulate treated fluid through the dosing system before shutdown.
Diesel generators. Stationary diesel generators with DEF systems typically have tanks from 5 to 15 gallons. The standard dose applies: one dose per 2.5 gallons. For generators that run infrequently or sit in storage between uses, pre-storage treatment is especially important given the static conditions that accelerate DEF crystallization.
Marine diesel engines. Diesel marine engines with SCR systems are treated at the same ratio: one dose per 2.5 gallons. NüDef is compatible with all diesel applications using ISO 22241 DEF, including marine engines. Treat before extended storage periods between boating seasons.
Agricultural equipment and construction machinery. Large DEF tanks on tractors and heavy equipment range from 20 to 100+ gallons. Treat at one dose per 2.5 gallons at every fill. For high-capacity tanks or fleet management of multiple units, bulk supply treatment through the DEF storage tank is the most operationally efficient approach.
Treating Bulk DEF Storage Tanks
Fleet operators using bulk DEF storage at fueling islands can treat the entire bulk supply rather than dosing individual vehicles. The same ratio applies: one dose of NüDef per 2.5 gallons in the bulk tank. For a 500-gallon bulk storage tank, that is 200 doses, or 20 bottles of NüDef.
Bulk treatment is operationally superior to per-vehicle dosing for fleets: every vehicle fueling from the treated bulk supply receives protected DEF automatically. There is no per-vehicle process change, no missed trucks, and no driver training required. The treatment also protects the bulk storage tank itself from crystallization, particularly important for outdoor bulk tanks exposed to seasonal temperature extremes.
Fleet accounts can contact NüDef at nudef.com/wholesale for wholesale pricing on case quantities for bulk treatment programs.
When to Add NüDef
Add NüDef at every DEF fill-up. Pour the appropriate number of doses directly into the DEF tank, then fill with fresh ISO 22241 DEF as usual. The order does not matter. NüDef can go in before or after the DEF. It mixes immediately and begins working on contact.
Two situations call for extra attention:
Pre-storage treatment. Before parking any vehicle for more than three weeks, add a full dose of NüDef even if the tank is not empty, then run the engine 10 minutes to circulate treated DEF through the dosing system. This is the most important dose for seasonal vehicles.
After a fault code or tank drain. If you have had a DEF fault code and are doing a drain-and-refill, add NüDef to the fresh DEF immediately after refilling. Do not add NüDef to degraded or contaminated fluid. Drain completely first, then refill with fresh treated DEF.
Cost Per Gallon Treated
At $19.99 per bottle treating 25 gallons, NüDef costs under $0.80 per gallon of DEF treated. For a pickup truck owner filling 5 gallons of DEF at each top-up, each treatment costs roughly $4.00, less than a gallon of diesel at most truck stops.
Against the cost of the problems NüDef prevents: a basic DEF system flush with injector inspection runs $200-$400. A dosing injector replacement is $300-$700 plus labor. SCR catalyst damage starts at $2,000. The cost per treatment is the lowest-cost intervention in DEF system maintenance by a wide margin.
