Diesel Fuel Additives FAQ

For everyday diesel use, XPD All-Season is our usual all-around recommendation. It combines lubricity, injector cleaning, water separation, corrosion protection, fuel stability, cetane improvement and preventive cold-weather support.

Choose a formula for your main need: XL for a focus on lubricity; Summer+ for warm-weather maintenance; Boost! for a stronger cetane increase; Winter for preventive anti-gel protection; or Single Clean for a one-tank injector-cleaning treatment. If fuel has already gelled, see Gel Melt emergency treatment.

See all diesel additive options or contact us for help choosing a formula.

Unopened diesel maintenance additive stored in good conditions can last up to about 5 years. After opening, we recommend using it within 1–2 years for best results.

Storage conditions matter: keep the container tightly sealed, upright and out of direct sunlight. Temperature, moisture exposure and how much product remains in the container can affect shelf life. This guidance is for the additive itself, not the storage life of treated diesel fuel.

Opti-Lube diesel fuel additives are formulated for diesel fuel systems and emissions equipment when used as directed. Use the correct product and dose, and follow your engine manufacturer’s fuel and maintenance requirements.

Warranty coverage is determined under the vehicle or equipment manufacturer’s warranty terms. For a warranty-specific question, check your owner’s manual or contact the manufacturer. We can help with product selection and application questions.

Our diesel fuel additives are intended for diesel-powered vehicles and equipment, including trucks, older diesels, agricultural machinery and modern diesel fuel systems. Choose a formula suited to your fuel, operating conditions and engine manufacturer’s requirements.

Use only in the fuel or application identified on the product label. Diesel fuel additives go in the diesel fuel tank; do not add them to gasoline, engine oil or a DEF tank unless a product is specifically labeled for that application.

Treatment rates vary by formula. Follow the current bottle label and the directions for your product and conditions. A treatment rate for XPD does not automatically apply to XL, Summer+, Boost!, Winter, Single Clean or Gel Melt.

For XPD All-Season at 1/4 US fl oz per gallon of diesel, use:

Measure the fuel quantity you are treating and stay within the labeled treatment range. See XPD product details.

Our diesel additives can be used with ULSD, biodiesel blends up to B20 and renewable diesel such as R99, following the directions for the specific formula. Use only fuels approved for your engine.

Cold-weather performance and treatment requirements can vary with fuel composition. For example, Gel Melt’s directions specify a higher dose for biodiesel blends up to B20. Follow the bottle label rather than assuming one dose applies to every fuel.

This does not authorize adding kerosene to a vehicle that does not allow it. Follow the engine manufacturer’s approved fuel specification.

No. Opti-Lube diesel fuel additives do not contain harmful alcohols, Teflon/PTFE, solid particles, or anything designed to remain suspended in the fuel that could harm the fuel system.

Some fuel additive ingredients may be alcohol-based for performance reasons, but Opti-Lube diesel additives do not contain harmful alcohols such as methanol or ethanol.

Cetane relates to how readily diesel fuel ignites during combustion. A higher cetane number can help improve cold starts, reduce ignition delay, smooth engine operation, and support more efficient combustion.

Diesel fuel quality can vary by supplier, region, and season. Winter-blended fuel and some lower-cetane fuels may leave certain engines feeling rougher, louder, harder to start, or less responsive. A cetane-improving additive can help offset those issues.

Our diesel maintenance formulas are compatible with each other, although each is designed to be used on its own. Some customers combine XL with Boost! to focus on lubricity and cetane improvement.

Follow each product’s directions. Do not assume that combining two products means you can double the dose or add their advertised benefits together. Contact us for help choosing a combination and treatment rate. Follow the separate label directions for emergency treatments such as Gel Melt.

For routine tank treatment, measure the recommended amount and add it directly to the diesel fuel tank before or during fueling. The incoming fuel and normal movement in the tank help mix the additive.

Follow the specific product directions. Preventive anti-gel products must be mixed into liquid fuel before it reaches its cloud point. Gel Melt has separate emergency tank and filter instructions; follow those directions and your equipment’s service instructions.

We recommend using Opti-Lube products as directed rather than combining them with another brand. We cannot confirm the compatibility, treatment rate or combined performance of every competing formula.

If your fuel already contains another aftermarket additive, contact us with the product name, amount used and fuel quantity before adding more.

• XPD All-Season: All-around maintenance with lubricity, cleaning, cetane improvement and preventive cold-weather support.
• XL Xtreme Lubricant: A focus on lubricity and fuel-system maintenance; choose a preventive anti-gel formula when needed for cold weather.
• Summer+: Warm-weather maintenance with lubricity, cleaning and cetane improvement.
• Boost!: A focus on a stronger cetane increase.
• Winter: Preventive anti-gel protection; add while the fuel is still liquid.
• Single Clean: A one-tank fuel-system and injector-cleaning treatment.
• Gel Melt: Emergency treatment for gelled fuel or frozen filters; not for continuous use.

See diesel additive options and follow the directions for your chosen formula.

Choose XPD All-Season for all-around maintenance with lubricity, injector cleaning, cetane improvement, water separation, corrosion protection, fuel stability and preventive cold-weather support.

Choose XL Xtreme Lubricant when lubricity is your main priority and you do not need an anti-gel formula. Both can be used for regular diesel maintenance. For cold-weather prevention, choose XPD or Winter as appropriate and add it before the fuel reaches its cloud point.

Stay within the treatment range on your bottle or product page. Using significantly more than directed does not automatically improve performance and can waste product.

Some labels specify a different rate for certain conditions, such as Gel Melt treatment of biodiesel blends. Use those product-specific directions. For injector-cleaning concerns, consider the labeled Single Clean treatment rather than heavily overdosing a maintenance formula. If you added much more than directed, contact us with the product, amount and fuel quantity.

Single Clean is designed for a one-tank cleanup of diesel fuel-system and injector deposits. One 8 fl oz bottle treats up to 32 gallons of ULSD; follow the bottle label.

After the cleaning treatment, return to your usual maintenance additive, such as XPD All-Season, XL or Summer+. Single Clean does not replace preventive anti-gel protection when cold conditions require it.

Our diesel maintenance additives are formulated for ULSD and are compatible with modern diesel fuel systems and emissions equipment when used as directed, including vehicles with diesel particulate filters (DPF), exhaust gas recirculation (EGR) and selective catalytic reduction (SCR).

Add diesel fuel additive to the diesel fuel tank only. Never add fuel additive to the diesel exhaust fluid (DEF/AdBlue) tank. Vehicles that use DEF still need the correct DEF in their separate DEF system.

Fuel additives do not replace required emissions-system service or guarantee a particular regeneration frequency. Follow your engine manufacturer’s fuel and maintenance requirements.

No. Opti-Lube fuel additives dissolve into the diesel fuel. They are not solid particles, so a normal fuel filter, including fine filtration systems, will not filter the additive out of the fuel.

Cold exposure can temporarily make some diesel maintenance additives cloudy or cause components to crystallize. This can be reversible and does not necessarily mean the product has expired.

For these formulas, warm the sealed bottle in a 90–110°F warm-water bath for 20–30 minutes, then shake well. Once the product returns to its normal appearance, use it as directed. Do not use an open flame, microwave or direct heat source.

If particles remain, the appearance does not return to normal, or you suspect water or other contamination, contact us before use. Have the product name and a photo available. Follow the label and Safety Data Sheet for the specific formula.

Keep containers tightly sealed, upright, in a cool, dry location and out of direct sunlight. Avoid prolonged exposure to extreme heat or freezing temperatures. Follow the product label and Safety Data Sheet.

If a diesel maintenance additive becomes cloudy or forms crystals after cold exposure, see the warming guidance above. Contact us if it does not return to its normal appearance or you suspect contamination.

Add a preventive anti-gel such as Winter or XPD while the diesel is still liquid and before it reaches its cloud point—the temperature where wax crystals begin to appear. Adding it before or during fueling helps it mix into the fuel.

Cold-weather results depend on the base fuel, treatment rate and conditions. Preventive anti-gel is not a thawing treatment. If fuel has already gelled or a filter has frozen, follow Gel Melt’s emergency directions and your equipment manufacturer’s service and priming instructions.

An appropriate additive may help when a problem relates to fuel quality or injector deposits. Smoke, unusual noise, rough running, power loss and warning lights can also have mechanical, electrical or emissions-system causes.

Follow the vehicle manufacturer’s warning and service instructions. Do not assume new symptoms are harmless cleaning or keep adding more treatment to correct them. Contact us with the exact product, amount used, fuel quantity and timing, and seek qualified diagnosis where needed.

If the fuel already in the tank was treated correctly, measure the next dose for the new fuel you add. If the remaining fuel is untreated or you are changing treatment rates for winter conditions, calculate for the fuel that needs treatment. Follow the specific formula’s label; contact us if you need help with the calculation.

Diesel maintenance formulas such as XPD, XL and Summer+ are intended for regular use at the labeled rate. You do not need to alternate treated and untreated tanks. Single Clean is a separate one-tank cleaning treatment, and Gel Melt is for cold-weather emergencies rather than continuous use.

No. Helping separate water from diesel is different from physically removing it. Maintain and drain the fuel/water separator as directed by the equipment manufacturer, and address water-in-fuel warnings. Do not assume that a maintenance additive kills existing microbial contamination or replaces assessment and treatment of contaminated fuel.

Results depend on base fuel, dose, engine condition and operating conditions. A test result or advertised increase is not a guarantee for every fuel batch or vehicle. Combining products or increasing the dose does not establish a proportional increase in cetane or fuel economy. An additive does not prevent every mechanical failure.

Items identified as empty refill or dosing bottles contain no additive. Check the selected package for the amount of additive and each included accessory; an additive-only gallon is different from a kit.

A dispensing pump is not a sealed transport cap. Keep the container upright and use its proper sealed closure for storage or travel. Match replacement pumps and accessories to the currently sold container before ordering.