Before Buying Fuel-Economy Products | How to Check Results and Avoid Wasted Spending

Thinking of buying something to improve fuel economy? First, record your current fuel economy and the condition of your car.

Without a baseline, you cannot tell whether a product helped or the roads simply happened to be less congested. Start by deciding both what the product is meant to change and how you will check it.

This article revisits the tire, additive and electrical-product themes of the former LANDMASTER column on fuel-economy products, with a new focus on pre-purchase checks and evaluating results. For diagnosing vehicle problems, see our separate guide to causes of poor fuel economy and inspection items.

Start with what you can check without buying anything.

Tire pressure, unnecessary luggage, abrupt acceleration and braking, driving routes and air-conditioning use are sensible starting points. JAF's eco-driving information also covers pressure checks, reducing unnecessary loads and gentle accelerator use. JAF eco-driving guidance (Japanese)

Do not simply raise tire pressure on your own judgment to improve fuel economy. Check the appropriate value for your vehicle and tires. Inspect oil and consumable components against the vehicle manufacturer's specifications.

If warning lights, a sudden drop in fuel economy, vibration or unusual noises are present, consult a workshop before adding products. Repairing a fault and evaluating further changes to a healthy vehicle are separate tasks.

The label “fuel-economy product” is not enough to choose by.

Do not select tires on fuel economy alone.

The Japan Automobile Tyre Manufacturers Association's labeling system displays rolling resistance and wet-grip performance separately. Both fuel economy and braking on wet roads deserve attention. JATMA tire-labeling system (Japanese)

Consider how much useful life remains in your current tires. Choosing a suitable tire when replacement is due is a different spending decision from replacing usable tires solely to pursue fuel economy.

For additives, check where they go and what they are intended to do.

Fuel additives and oil additives are added in different places. Even among fuel additives, products primarily intended for cleaning differ from those intended for fuel conditioning. Check each product's application and conditions, not just its ingredient name.

Our guides to fuel-additive types and selection and engine oil additives explain these distinctions. We do not recommend evaluating products by increasing doses or mixing several products on your own judgment.

To evaluate fuel economy, record it consistently.

First, choose a comparison period. Collect several refueling records before and after use under driving conditions that are as similar as possible. Avoid comparing one exceptional result with your usual average.

A common method is to divide the distance covered between refueling points by the amount of fuel added, using the same refueling basis. For example, 400 km followed by a 40 L refill gives a calculated 10 km/L. Refilling amounts can vary, so using the total distance and fuel over several intervals reduces the influence of a single difference.

Follow the vehicle and refueling equipment instructions. Do not force extra fuel into the tank for comparison purposes. If using the vehicle's fuel-economy display, keep that method separate from calculations based on refueling quantities and use the same method throughout.

Changing tires or oil at the same time as introducing an additive makes it harder to separate the causes of any change. Do not postpone necessary maintenance: record it and recognize that the period is not a simple like-for-like comparison.

Separate “it feels lighter” from “fuel economy improved.”

Recording changes in driving feel is useful. Feeling more responsive, however, does not by itself demonstrate lower fuel consumption. Fuel economy, acceleration time, sound, vibration and control feel are different evaluation items.

Equally, there is no need to reinterpret the numbers as an improvement when there is no clear fuel-economy difference. Record that no difference was confirmed under those conditions.

Consider the usable quantity, not just the purchase price.

For a product used regularly, comparing how many liters of fuel it treats can be more useful than comparing bottle prices.

Product price ÷ fuel volume treated = product cost per liter of fuel

For example, a product costing JPY 2,000 that treats 400 L costs JPY 5 per liter of fuel. This is a calculation example, not a real product price or a claim of savings.

If fuel economy changes from 10 km/L to 11 km/L, the km/L figure rises by 10%. But fuel needed for the same 100 km falls from 10 L to approximately 9.09 L, a reduction of about 9.1%. The percentage increase in fuel economy and the percentage reduction in fuel consumption are not the same.

To assess whether costs can be recovered, use your own mileage, measured fuel-economy change, fuel price and recurring product costs. Someone else's best result does not establish that a product will pay for itself.

Check NEXT SCIENCE products and records.

For a fuel-based approach to condition maintenance, see the GERHON guide by fuel type. Gasoline, diesel and kerosene versions are separate products.

GERHON's gasoline technical records and diesel technical records present measurements and usage records obtained with the products and conditions of their time. The current series builds on improvements to earlier GERHON products, but those historical numbers are not guarantees for your vehicle.

For ORBITRON, which focuses on the electronic environment and driving feel, also distinguish the design objectives from verification records. When evaluating a product specifically for fuel economy, first check whether the available results actually assess fuel economy.

Conclusion: decide what you want to verify before deciding what to buy.

Complete necessary servicing, record the current condition and consider products one at a time according to your purpose. After use, assess results with the same method. This sequence avoids leaving your decision to the biggest number in an advertisement.

Find car, motorcycle and machinery products by application / Ask about compatibility and usage conditions

Sources and revision history

Re-edited on September 7, 2026, from the themes of LANDMASTER's January 29, 2018 column, Fuel-economy products (Japanese). Rather than reproducing its wording unchanged, this edition distinguishes general checks supported by JAF and JATMA's published information. Those organizations have not thereby certified the effectiveness of our products.