Real-World Mileage Testing with a Volkswagen TDI

Customers sometimes ask whether a diesel fuel additive can improve fuel economy. The most honest answer is that results vary. Fuel quality, driving habits, vehicle condition, route, load, weather, and maintenance can all affect mileage.

One Real-World Example

This older customer-style comparison used a stock 2010 Volkswagen TDI driven on the same roads day after day. All products were used at the normal recommended dose.

Results reported in that test were:

No additive: 567 miles, 14.072 gallons, 40.29 mpg

Power Service Diesel Kleen: 604.3 miles, 14.369 gallons, 42.06 mpg

Opti-Lube XL Extreme Lubricant: 615.0 miles, 14.206 gallons, 43.29 mpg

Opti-Lube XPD: 635.7 miles, 14.245 gallons, 44.63 mpg

How to Read These Results

This type of test is useful as a real-world example, but it should not be treated as a guaranteed result for every vehicle. A diesel additive can help support lubricity, injector cleanliness, cetane, water separation, corrosion protection, and fuel quality, but fuel economy changes will vary from one engine and driving situation to another.

Best Takeaway

For most customers, the best reason to use a diesel fuel additive is long-term fuel system care and consistent fuel quality. If improved fuel economy follows, that is an added benefit.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Which Opti-Lube Diesel Fuel Additive Should I Use?

Choosing the right diesel fuel additive depends on your main concern. Some customers want one all-around additive. Others are focused on maximum lubricity, stronger cetane, cold-weather protection, or a one-time fuel system cleaning treatment.

Quick Product Guide

XPD All-Season

XPD All-Season is our most popular diesel fuel additive because it covers the widest range of needs in one product. It supports lubricity, injector cleanliness, water separation, corrosion protection, fuel stability, cetane improvement, and cold-weather performance.

XL Extreme Lubricant

XL Extreme Lubricant is the best choice when maximum lubricity is the main goal. It is popular in warm climates, older diesel engines, equipment, and applications where fuel system wear protection is the top priority.

Summer+

Summer+ is a warm-weather formula focused on lubricity, cetane, detergency, and performance. It is a good option when anti-gel protection is not needed.

Boost!

Boost! is the best option when the main goal is cetane improvement. Higher cetane can help with cold starts, smoother combustion, reduced ignition delay, and overall drivability.

Winter

Winter is designed for stronger cold-weather anti-gel protection. It should be added before fuel reaches its cloud point or begins to gel.

Single Clean and Gel Melt

Single Clean is a stronger one-tank cleaning treatment for injector deposits, smoke, rough running, or fuel system cleanliness concerns. Gel Melt is an emergency product for diesel fuel that is already gelled.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Feeling Like Your MPG and Power Might Be Down?

If your diesel feels down on power, seems louder than normal, smokes more than usual, or has lost fuel economy, fuel system deposits may be part of the problem. They are not the only possible cause, but they are common enough to be worth considering.

Why Deposits Matter

Modern diesel injectors operate at very high pressures and use very small openings to atomize fuel. When deposits form on injector tips or inside the injector, the spray pattern can be affected. That can lead to rougher running, more smoke, reduced responsiveness, and less efficient combustion.

Where Single Clean Fits

Opti-Lube Single Clean is designed as a stronger one-tank cleaning treatment. It can be used when injector deposits, smoke, rough running, or fuel system cleanliness are the main concern. After that cleaning treatment, most customers return to a regular maintenance additive such as XPD All-Season, XL Extreme Lubricant, or Summer+.

When an Additive May Not Fix It

If the issue is caused by a mechanical problem, boost leak, air restriction, bad sensor, tuning issue, emissions-system problem, or worn component, an additive will not correct the root cause. In those cases, diagnosis and repair may be needed.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Q&A: Can I Mix Multiple Opti-Lube Diesel Additives?

In short: yes, Opti-Lube diesel additives can generally be mixed. The main thing to remember is that each product is designed for a purpose, so mixing products is not always necessary.

Common Combinations

XL Extreme Lubricant and Boost! can make sense when a customer wants strong lubricity and a stronger cetane increase. XPD All-Season and Winter can also be used together when a customer wants XPD’s year-round benefits plus stronger cold-weather anti-gel protection.

When Mixing May Not Be Needed

Mixing XL and XPD All-Season is usually not necessary because both provide strong lubricity benefits. Summer+ may also provide the balance some customers are trying to get by mixing XL and Boost!.

Avoid Overdoing It

Using a little more than the recommended amount is usually not a concern, but significantly overdosing generally does not provide extra benefit and may not be cost-effective. Follow the directions on the bottle or product page for best results.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

When Should You Use Opti-Lube Single Clean?

Opti-Lube Single Clean is designed as a stronger one-tank cleanup treatment for diesel fuel injection system deposits. It can be used in modern common rail systems as well as older diesel fuel systems.

What Single Clean Is For

Single Clean is a good choice when injector deposits, rough running, smoke, loss of responsiveness, or fuel system cleanliness are the main concern. It is not meant to replace every-tank maintenance additives for all customers; it is a stronger cleaning treatment used when needed.

How It Differs From Maintenance Additives

XPD All-Season, XL Extreme Lubricant, and Summer+ are commonly used as regular maintenance additives. Single Clean is focused more specifically on cleaning. After using Single Clean, most customers return to their regular additive for ongoing lubricity, water separation, corrosion protection, cetane, and maintenance cleaning.

What to Expect

If the problem is related to fuel system deposits, a cleaning treatment may help improve operation. If the issue is mechanical, air-related, tuning-related, or emissions-system related, an additive may not resolve the root cause.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Why Is a Diesel Fuel Additive So Important?

Diesel fuel quality can vary by supplier, region, season, storage conditions, and fuel type. A good diesel fuel additive helps support fuel quality and can address several concerns that matter to modern and older diesel engines.

Lubricity

Lubricity is one of the most important reasons customers use diesel fuel additives. Fuel pumps and injectors rely on the fuel for lubrication. XL Extreme Lubricant is the best choice when maximum lubricity is the main goal, while XPD All-Season provides strong lubricity as part of a broader all-around formula.

Cetane

Cetane relates to how readily diesel fuel ignites during combustion. A higher cetane number can help with cold starts, smoother operation, reduced ignition delay, and drivability. Boost! is the best choice when maximum cetane improvement is the main goal.

Cold-Weather Performance

Cold temperatures can cause wax in diesel fuel to form crystals that restrict flow, especially at the filter. Winter is designed for severe cold-weather anti-gel protection, while XPD All-Season provides cold-weather support as part of an all-around additive.

Deposit Control

Modern diesel fuel systems operate at high pressures and have very small injector openings. Deposit control helps maintain spray pattern and fuel system cleanliness. Single Clean is a stronger cleaning treatment, while regular maintenance additives help keep the system clean over time.

Water Separation and Corrosion Protection

Water in diesel fuel can cause corrosion, filter plugging, microbial growth, and fuel system problems. Opti-Lube diesel additives are designed to support water separation so the fuel/water separator can do its job.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Why the Disclaimer About Oil Fortifier in Gasoline Engines?

Opti-Lube Oil Fortifier is designed as a high-tech lubrication enhancer for engine oil. The caution around gasoline engines is mainly related to zinc-containing anti-wear chemistry and the potential long-term sensitivity of catalytic converters.

Why Zinc Is Mentioned

Zinc-based anti-wear chemistry has long been valued for protecting engine parts under load. However, modern gasoline engines often use catalytic converters and emissions equipment that can be sensitive to certain oil-derived contaminants if enough oil reaches the exhaust stream.

Why We Use a Disclaimer

We have used cautious language because every engine and emissions system is different. In a healthy engine with minimal oil consumption, very little oil should reach the exhaust. In an engine with significant oil consumption, worn rings, or other problems, oil-derived additives may have a greater chance of reaching emissions components.

Best Use Guidance

Follow the product label directions and use the correct product for the application. For modern gasoline engines with catalytic converters, use caution and consider whether an oil fortifier is appropriate for that engine.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Why Do I Need a Diesel Fuel Stabilizer for Bulk Tanks?

Diesel fuel in bulk tanks can sit for weeks, months, or longer before it is used. During that time, fuel can be affected by oxidation, water contamination, heat, microbes, and sediment formation.

Why Stored Fuel Changes

Fuel storage problems are often caused by a combination of time, oxygen exposure, temperature swings, water, and contamination. As fuel ages, it may darken, form gums or sediment, plug filters, and perform poorly.

Best Practices for Bulk Tanks

• Keep tanks as clean and dry as possible.
• Reduce water entry from condensation, leaks, or poor caps and vents.
• Inspect and drain water separators when needed.
• Use a fuel stabilizer before long-term storage problems develop.
• Rotate fuel when possible instead of letting it sit indefinitely.

Where Preserve Fits

Opti-Lube Preserve is designed for customers who need fuel stability for stored diesel. It is a good choice for bulk tanks, standby equipment, seasonal equipment, and fuel that may not be used quickly.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Tired of Measuring Diesel Additive for Every Tank?

Measuring diesel additive every time you fill up does not have to be complicated. The key is to know your tank size, understand the treatment rate, and use a container or dosing method that makes the amount easy to repeat.

Use the Right Treatment Rate

Treatment rates vary by product, so follow the directions on the bottle or product page. For example, XPD All-Season is commonly used at 1/4 oz per gallon of diesel fuel.

Make Dosing Easier

• Keep a dedicated measuring bottle in the vehicle.
• Pre-measure common amounts for your usual fill-up size.
• Add the product before or during fueling when possible.
• Use the same routine each time to avoid underdosing or overdosing.

What If You Add a Little Too Much?

A small amount over the recommended dose is usually not a concern. However, significantly overdosing generally does not provide extra benefit and is usually not cost-effective.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

What Is Cetane and Why Does It Matter?

Cetane relates to how readily diesel fuel ignites during combustion. In simple terms, a higher cetane number usually means the fuel ignites more easily and with less delay after injection.

Why Cetane Matters

A higher cetane number can help improve cold starts, reduce ignition delay, smooth engine operation, reduce diesel knock, and support more efficient combustion. The benefit you notice depends on the fuel, engine, temperature, and operating conditions.

Does Higher Cetane Improve MPG?

Some customers report improved fuel economy when cetane is improved, but results vary. Fuel quality, vehicle condition, load, driving habits, idle time, weather, and route can all affect mileage.

Which Opti-Lube Product Is Best for Cetane?

Boost! is the best choice when maximum cetane improvement is the main goal. Summer+ and XPD All-Season also provide cetane benefits as part of a broader additive package.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.