Like always I’m learning something new when Scott Daniel takes a moment to post to the Diesel Vanagon list. Thanks!
“I am adamant that a fuel additive must be used in pump diesel fuel. The kind that ‘improves combustion, reduces smoke, improves power.’”
So here is what I’m hearing. Anyone with a VW diesel should be adding a fuel additive which will improve the combustion quality of the diesel fuel they are burning. Over long usage, the fuel additive will improve engine performance, preserve the fuel tank and lines, and decrease wear and tear on engine internals (the injectors, block and pistons).
So I’m searching and there are many different types of diesel fuel additives. Some of them are designed to lower the gel point of the fuel and from what I can tell these usually have a fair amount of ethanol in them. Some are simply lubrication. In either case I don’t believe that this is what Scott is referring to however; rather I think he’s indicating a Cetane improvement mix. Wikipedia has a pretty good description of what this is, but to summarize Cetane is a measure of diesel fuel’s ignition delay. The higher the cetane value is the shorter the ignition delay. And from further reading cetane seems similar to octane rating which many of us are already familiar with. Here’s some standard values, the next time I fill up (probably with diesel #2) I’ll see if the cetane value is on the placard.
| Regular diesel | 48 |
| Premium diesel | 55 |
| Biodiesel (B100) | 55 |
| Biodiesel blend (B20) | 50 |
| Synthetic diesel | 55 |
http://alternativefuels.about.com/od/researchdevelopment/a/cetane.htm
What really got me interested in this value is the following statement from the link above “running a diesel engine on fuel with a lower than recommended cetane number can result in rough operation (noise and vibration), low power output, excessive deposits and wear, and hard starting.” So having a higher cetane value than is recommended for you engine does no good, at least for combustion, but having fuel with a lower cetane value can actually harm engine performance as well as reduce its life. Sounds a lot like what happened to Zeno’s old 1.6l.
So next I went looking specifically for a cetane additive that might meet these qualifications more or less intent on finding how much I might be able to improve the average cetane ratings of the above fuel formulations. AMSOIL Cetane Boost Additive is the brand that I’m working from at the moment specifically because they not only talk about the benefits of the additive (which is well documented elsewhere), but also because this manufacture quantifies the improvement in cetane value per fuel/additive mix ratio. Somewhere on average between 3 and 7 points depending on how much you add.
If the cetane value for the fuel you pump is on the fuel pump placard you should be able to calculate your optimum additive ratio based on that known value and the cetane value the engine manufacture recommends for your engine. If, for example, you’re pumping “regular diesel” with a cetane value of 48 and your engine manufacture recommends that you run fuels with a cetane value of 51 then if you used the additive listed above you’d only add one fluid ounce per 10 gallons (1oz/10gal) of fuel pumped. Say, however, your engine is rated for a cetane value of 55 you’d effectively have to double the amount of additive mixed with the fuel (1oz/5gal) to get you to the optimum cetane operating rating. You see how this knowledge should affect your supply of additive?
Now all I need to know is the cetane value that Volkswagen recommended for my new 1.9l NA engine. Better yet, what Scott recommends. The former is probably pretty close to the latter. Very cool information, this is going in Zeno. Also recommendations of specific brands and mixes are welcome.
