What You Can Put in Your Gas Tank to Improve Mileage—And What You Shouldn’t

If you’re hoping for a pour-in miracle, there isn’t one: the best you can put in your gas tank for better mileage is quality gasoline that meets Top Tier detergent standards, the manufacturer-recommended octane, and—if deposits are suspected—an occasional PEA-based fuel system cleaner. Ethanol-free gasoline can add a small efficiency bump where available, but often isn’t cost-effective. Most “MPG booster” additives don’t work and some can damage your engine or emissions system.

What Actually Helps Inside the Tank

Only a few fuel choices and additives have credible evidence behind them. These don’t create dramatic gains, but they can prevent or undo the small efficiency losses that accumulate with deposit buildup or subpar fuel.

• Top Tier gasoline: Brands that meet the “Top Tier” standard contain higher levels of detergents that keep injectors and combustion areas cleaner. Independent testing by AAA has shown that non–Top Tier fuel can lead to more deposits, which over time can trim efficiency; using Top Tier fuel helps prevent that and may recover a small amount of lost MPG.
• The right octane for your engine: Use the octane specified in your owner’s manual. If your engine requires premium, using regular can reduce efficiency under load due to knock control. If your engine only recommends premium, you may see a slight MPG benefit with premium in hot weather, at altitude, or during heavy loads—but many drivers won’t notice a meaningful difference in everyday commuting.
• PEA-based fuel system cleaner (occasionally): Polyetheramine (PEA) is the additive chemistry with the strongest track record for cleaning injectors and combustion chambers. Well-regarded options include Chevron Techron Concentrate Plus, Gumout Regane Complete Fuel System Cleaner, and Red Line SI-1. Use per label directions (often every 3,000–5,000 miles or a couple of times a year). Note: these cleaners won’t clean intake valves on many direct-injection engines, because fuel doesn’t wash over those valves.
• Ethanol-free gasoline (E0), if practical: E10 (the common blend) has about 3–4% less energy than pure gasoline. E0 can return roughly that much MPG, but it often costs more and isn’t available everywhere, which can erase the savings. Check local pricing and legality in your area.
• Fuel stabilizer for storage: If a vehicle will sit for months, a stabilizer helps preserve fuel quality and prevent varnish that can hurt performance later. It won’t boost mileage in normal, frequent driving.

Expect modest results: preventing or reversing deposit-related losses can net a 0–3% improvement in typical cases, occasionally more if the system was heavily fouled. Sustained gains beyond that from in-tank products are unlikely.

Additives and Myths That Won’t Improve MPG—and Can Cause Harm

Many “boosters” promise big mileage gains. Most are ineffective, and some can damage fuel system components, oxygen sensors, or catalytic converters, or violate emissions laws.

• Acetone, paint thinners (toluene/xylene), or solvents: Can degrade seals and hoses, pose safety risks, and provide no reliable MPG benefit.
• Mothballs (naphthalene or paradichlorobenzene): Combustion byproducts can damage the engine and emissions system; this is unsafe and illegal in many jurisdictions.
• ATF, two-stroke oil, diesel, or kerosene in gasoline: Fouls plugs and catalysts, risks injector damage, and offers no MPG improvement.
• Sugar or water: Urban myths—sugar doesn’t dissolve in gasoline; either can cause expensive repairs.
• Octane boosters in engines not knocking: Higher octane doesn’t contain more energy; if your engine doesn’t need it, you won’t gain MPG.
• Fuel-line magnets, pills, or tablets: No credible evidence supports mileage improvements.

Using unapproved additives can void warranties, create safety hazards, and lead to costly repairs that dwarf any imagined fuel savings.

How to Tell If a Cleaner Might Help

A PEA-based cleaner can be worthwhile when there are signs of injector or combustion deposits. Look for patterns over multiple tanks rather than a single fill-up anomaly.

• Noticeable drop in MPG versus your long-term baseline, not explained by colder weather, short trips, new tires, or roof racks.
• Rough idle, hesitation, or sluggish throttle response, especially on port-injected engines.
• Frequent short-trip driving or extended use of non–Top Tier fuel, which can allow deposits to accumulate.
• Direct-injection engines with high mileage: cleaners can help injectors and combustion chambers, but won’t clean DI intake valves; that requires other service methods.

If symptoms improve after a cleaner treatment and a couple of tanks of Top Tier fuel, you likely addressed deposit-related issues. Don’t overdose—follow the label and avoid back-to-back heavy treatments unless specified.

Cost-Benefit: When It Makes Sense

Run the numbers. If ethanol-free fuel costs 30 cents more per gallon and returns 3% better MPG on a car that gets 30 mpg, the break-even price spread is roughly equal to that 3% (about 10 cents at $3.30/gal). If the premium is higher, you’re likely paying more for the same or slightly better range. PEA cleaners typically cost $7–$15 per treatment; if they recover even 1–2 mpg over a few thousand miles in a deposit-prone car, they can pay for themselves. In a well-maintained car already on Top Tier gasoline, the gains may be negligible.

Beyond the Tank: The Biggest MPG Gains Come Elsewhere

While the question focuses on the gas tank, the most effective mileage improvements come from driving and maintenance. These steps typically dwarf any additive-related gains.

• Smoother driving and slower cruising speeds: Avoid hard accelerations; reduce highway speed by 5–10 mph.
• Tire pressure and alignment: Keep tires at spec and fix misalignment that scrubs away efficiency.
• Reduce weight and drag: Remove cargo you don’t need; take off roof racks/boxes when not in use.
• Timely maintenance: Fresh spark plugs as specified, clean air filter (only helps MPG if the old one was restricted), healthy O2 sensors, correct oil grade.
• Plan trips and avoid idling: Combine errands, use navigation to dodge congestion, and limit warm-ups.

These habits can improve real-world MPG by 10–30% in many scenarios—far more than any in-tank product can deliver.

Bottom Line

For better mileage from what you put in your tank, stick to Top Tier gasoline, the octane your engine calls for, and an occasional PEA-based cleaner if deposits are suspected; consider ethanol-free only if the price premium makes sense. Steer clear of “miracle” additives. The largest and most reliable MPG gains still come from driving habits and basic maintenance, not bottles at the pump.

Summary

There’s no additive that reliably boosts MPG beyond modest, situational gains. Use high-detergent Top Tier fuel, the correct octane, and a reputable PEA cleaner when needed; ethanol-free can add a small bump if cost-effective. Avoid unproven or risky additives. Focus on driving and maintenance for the biggest savings.

Will fuel injector cleaner improve gas mileage?

A good fuel injector cleaner can help improve gas mileage, vehicle performance, and lower maintenance costs by keeping the engine clean. A clean engine delivers more power and better performance because it doesn’t have to work as hard.

What can I put in my gas tank to get better gas mileage?

The best I have heard are gas line magnets, fuel tank tablets, turbonator, and HHO generator. Gas line magnets are strong permanent magnets surrounding the gas line to align the gasoline molecules, making them burn more efficiently. Fuel tank tablets (or sometimes gas snakes) are put down the tank filler.

What trick gets the best gas mileage?

What are easy hacks to make my car have better gas mileage? The easiest one is to slow down. Driving slower will almost always save you gas, especially from about 40mph and up. Accelerate slowly, but steadily. No jackrabbit starts. Don’t stop or slow down if you can help it. slowing down to speed up again wastes fuel.

How to increase miles per gallon on a car?

To improve your car’s MPG, reduce its weight, maintain proper tire pressure, ensure your engine is in good working order with regular maintenance (like checking air filters and spark plugs), and adopt fuel-efficient driving habits such as maintaining a steady speed, minimizing idling, using cruise control, and avoiding aggressive acceleration. 
Vehicle Maintenance

• Maintain Tire Pressure: Opens in new tabProper tire inflation is crucial, as underinflated tires increase rolling resistance and reduce fuel economy. 
• Replace Air Filter: Opens in new tabA clogged air filter can restrict airflow to the engine, leading to reduced fuel efficiency. 
• Check Spark Plugs: Opens in new tabWorn spark plugs can cause engine misfires and poor fuel economy, so ensure they are regularly checked and replaced. 
• Regular Maintenance: Opens in new tabKeep up with your car’s regular maintenance schedule, including oil changes, which helps the engine run more efficiently. 
• Proper Alignment: Opens in new tabEnsure your wheels are properly aligned, as misalignment can increase tire wear and fuel consumption. 

Driving Habits

• Drive Smoothly: Opens in new tabAccelerate gently and brake smoothly to conserve fuel. 
• Maintain Steady Speed: Opens in new tabUse cruise control on the highway to maintain a consistent speed, which is more fuel-efficient than constant acceleration and deceleration. 
• Minimize Idling: Opens in new tabTurn off your engine when you’ll be stopped for an extended period (e.g., more than a minute) to save fuel. 
• Reduce Weight: Opens in new tabRemove unnecessary items from your car, such as those in the trunk or back seat, to decrease the energy the engine needs to move the vehicle. 
• Improve Aerodynamics: Opens in new tabKeep your windows up, especially at highway speeds, to reduce drag and improve fuel efficiency. 
• Use Air Conditioning Sparingly: Opens in new tabRunning the air conditioner can consume a significant amount of fuel, so use it only when necessary. 

Route Planning 

• Plan Your Routes: Plan your trips to avoid heavy traffic and minimize unnecessary travel.