There are many, many different fuel additives available for diesels. A quick google search or a stroll down the aisle at your local parts store will give you plenty of options from which to choose. Are they necessary and which one is the best?
Diesel fuel additives are designed to de-gel your fuel, add lubricity (a fuel’s ability to lubricate engine parts), add cetane, and even remove the water from your fuel. And you, the consumer, have no way of telling if a particular additive actually does what it says. Or even if additives are even necessary in the first place.
There’s longstanding debate on this topic. Some say that additives are essential and, without fail, add a product at every fill-up. Others think that the added lubricity isn’t really necessary, stating that most of the effect of these additives is placebo, and that the fuel does a good enough job on its own.
On the one hand, it’s worth considering the highly variable quality of fuel in the US. I personally, on a cross-country trip, have experienced the dark side of fuel quality, getting fuel so bad at one station in Wyoming that my car simply refused to run a hundred miles later. Only after replacing the fuel filter could I get my car back on the road. Cetane content changes from region to region, and with the introduction of ULSD (ultra low sulfur diesel), diesel fuel lost a big chunk of its natural lubricity. When refiners remove the sulfur from diesel to make ULSD, it also removes aromatics that both help lubricate the fuel system and keep injection pump and other seals healthy. Much of the diesel fuel in the US is used in trucks and big rigs, and these engines are much less sensitive to fuel quality in comparison to TDIs. The high pressure fuel pump (HPFP) in common rail VWs starting in 2009 is especially sensitive to fuel lubricity, and pump failure results in a major (and expensive) repair, as it can spread debris throughout the fuel system. Much of the fuel in the US does not meet Bosch lubricity standards for long HPFP life.
On the other hand, many of these products might just be snake oil—totally ineffective mystery petroleum product, a waste of $5. Can “Xtreme Cetane” really make my car more powerful? Or can “Icy Flow” actually help my car to start in subzero temperatures? I have no idea. Be wary.
Taking all these factors into account, our position at idparts is this: if you want to spend the money, it’s better to be safe than sorry. Selected additives do follow through on their claims—they add lubricity, decrease gelling, or add cetane. They can act as insurance, guaranteeing that the fuel in your car has the qualities your car needs. Below we’ve listed a few products we use and trust.
This company started way back in the 1800s as a precision machine screw manufacturer, and in the early 1940s started making rotary fuel pumps for diesel engines. Stanadyne Performance Formula comes in many different packages: half gallons, 8 oz. bottles, and 16 oz. bottles., and has a solid reputation for effectiveness in increasing lubricity and fuel economy. We also stock a Junior formula, which is a product designed for ULSD and to be used in conjunction with up to 5% biodiesel. It increases lubricity and the demulsifying properties of the fuel, but doesn’t add cetane or have anti-gel properties.
Optilube is generally considered to be among the best fuel additives around. They have products that run the gamut, including additives that add cetane, lubricity, and a winter formula. Plus, they even have a box with a lid to protect your car from spills.
Power Service is another quality brand, and this product provides a cetane boost which allows diesels to start in lower temperatures. Diesel fuel gels when it gets cold, which makes it harder to ignite. This additive makes the fuel resistant to gelling and raises the cetane, both which help a car start in low temps. Try Diesel Kleen + Cetane boost in the silver bottle for normal temperatures.