Not all fuel additives work, so it is important to know which gas-treatment options are worth your hard-earned money.
When we talk about fuel additives, we have to differentiate between additives added when the fuel is manufactured and those added by people to their gas tanks. Every fuel treatment and gas additive added to fuel distributed in the USA at the point of manufacture is regulated by federal regulations under Section 211 of the Clean Air Act. The Environmental Protection Agency (EPA) requires that any substance that is added as a gas treatment when manufacturing gasoline must be registered and may require testing. They are designed to be burnt away completely with the fuel in the cylinders' combustion chamber.
But what are fuel additives? They are additional products added to the gasoline or diesel to perform tasks such as reducing harmful deposits. It is very important to note that the Clean Air Act already requires that deposit-control additives - DCAs - be added to our gasoline before it reaches our gas stations. So, there is already a blend of federal-approved and -tested additives added to your fuel even before you add anything you bought from the parts store to your fuel tank. This begs the question of whether these after-market additives are even necessary.
In terms of the additives added during the manufacturing of gas or diesel fuel, they vary, but may include some or all of the following:
Let's have a look at the most common after-market additives available commercially and what they do when added to your full gas tank:
Because of the different properties of diesel, a diesel-fuel additive performs different functions. Depending on the time of year, such blends may be modified as necessary, most often at refinery level. In the distribution system, some additives are added that may reduce drag, which, in turn, increases pipeline capacity. Corrosion reducers, deicers, detergents, and lubricity improvers are commonly added to diesel fuel at the distribution level. Many an aftermarket diesel additive makes similar claims to its gasoline counterpart. You can also read more about diesel exhaust fluid such as AdBlue here.
Neither gasoline nor diesel remains stable and unaffected when stored in an unused state unless storage conditions are totally airtight. Fuel can actually spoil in as little as a month. Therefore, fuel stabilizers are added by fuel distributors. But what is a fuel stabilizer? It maintains the fuel's condition for as long as it is expected to be stored before being pumped into a fuel tank. If you are storing fuel at home or your car is going to be unused for a long time, after-market fuel stabilizers are available to bond with your fuel and prevent, for example, degradation, resin formation, and evaporation. This should allow you to keep gasoline for around one to three years.
Unfortunately, many of the claims that fuel additive producers make are overblown, so do fuel additives work, or are they a waste of money? Some EPA-approved additives can be effective and have been proven to clean valves of carbon deposits and fuel injection systems of other contaminants. The best fuel additive is one that actually works to at least somewhat improve your engine's performance and efficiency. Treat claims of huge improvements with circumspection, as these are almost never true. The improvements are incremental at most and often hard to detect. This holds true for all types of vehicles, whether it's a diesel pickup like a Ford F-250 or a gas-powered sedan such as a Honda Accord.
For example, gas mileage improvements are often due to more economical driving, rather than the additives. Unfortunately, buyer's remorse and psychology play their roles too. Lastly, that so-called gas tank cleaner may be able to dissolve some impurities in your tank, but for the majority of gunk that enters your fuel tank, nothing will help except dropping the tank and cleaning it physically.
So, what's the best fuel treatment for your vehicle? It's the one that actually brings about an improvement in your engine's performance with regard to horsepower, efficiency, and/or emissions. That said, these improvements will likely be too small to accurately measure and difficult to quantify. When you choose additives, follow this guide as a helpful tool, be skeptical, and buy only EPA-approved products. How to use them is important, too, so follow the instructions. Incorrect or subpar additives can damage the high-pressure fuel systems on premium cars, or cause engine damage. For most new cars, the additives already present in gas station petrol are more than sufficient.
If your car's fuel is going to be sitting in the tank unused for a long time, adding a fuel stabilizer is justified. When your engine is running unevenly or uses more fuel, an injector cleaner may justify its cost if it manages to solve the problem. However, not all running problems can be solved with additives; for example, high diesel consumption is often caused by clogged air filters which you will need to replace rather than just adding something to your fuel tank.
You can almost summarily dismiss those 10% to 20% claims. You might see an improvement of a few percentage points - realistically less than 5% - if your injectors are responsible for affecting your fuel economy and if the cleaning agent really works. It's very difficult to verify small gas mileage improvements, as there are so many other variables.
The best way to gauge good quality is to only buy products that have been approved by the EPA. Trusting unverified, unaccredited claims of quality is a surefire way to get cheated out of your money.
The additive must be properly mixed with the fuel - and in the correct ratio. Calculate how much additive you need per gallon and the total to add to your vehicle's tank size. Your fuel tank should be nearly empty before you refuel. Drive to the filling station, switch off your vehicle, and add the correct amount of additive before you fill the tank. This will allow the additive and fuel to mix properly. Repeat the process when you are nearly out of fuel, as needed.