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Friday, June 13, 2014

You burn WHAT in there??

Diesels burn oil.  In fact Cummins Engine Co. used to advertise its diesels as 'oil engines'.  These days there is alot of info out there on biodiesel, but not much good info on what else can be used as fuel in diesel engines.  Alot of owners of diesel powered machines have asked me what else can be used as a fuel source for lower cost without resulting in extra time and money in repairs, sacrificing reliability, or causing any degradation in performance. So lets talk about some diesel fuel alternatives for a minute here.  

One of the beauties of a diesel engine is that they can be fueled by nearly any type of light to medium viscosity oils. The idea that these engines can burn waste or new oils, vegetable oils, mineral or petroleum oils, most light paraffins, and synthetic oils all the same. So long as the oil you want to burn for fuel is very well filtered, most engines won't have any issues running on various oils or combinations thereof. 

The importance of filtering the oil to a very fine degree and removing all the water and other contaminants cannot be overstated. Filtering to remove particles over about 5 microns and smaller is best. Over 10 micron particle size can cause serious, rapid wear on fuel pumps. Most diesels have a much finer fuel filter near the engine that will remove most foreign material down to between 2 and 5 microns, so these filters will prevent most damaging particulates from entering the very tight tolerance injection pump.  

Since these pumps produce between 20,000 psi on older models and over 40,000 psi on newer diesels, clearances inside injection pumps are indescribably tight. There is literally NO room inside an injection pump for any non-fuel material. Any tiny bits of particulate matter can mean immediate damage and possibly massive repair costs. Injection pumps wear out from use, plain an simple, but by spending the money on top quality filters/ water separators, we can extend the life of these pumps by many times.  

In 2007, the US government poked us in the eye again by forcing the refineries to remove the lubricative sulfur salts from diesel fuels and sell it to us as low-sulfur diesel (LSD). Most of these sulfur compounds were removed to eliminate the slightly brimstone-like smell of diesel exhaust, and also to prevent some moderate  amounts of sulfur related pollution. This is a complete waste of money, time and resources in my opinion. We were given no choice in the matter though, and now our injectors and pumps are suffering the damage caused by this lack of these natural lubricants. Thus, we need to add lubrication to the fuel since the refineries are taking it out. Sure, we save a bit of pollution and some stinky fart smells, but really we gain nothing- it costs more over the long term to use only this fuel because of the additional cost of repair, maintenance expense and price of replacement parts that fail due to metal grinding on metal.  Ask any fleet mechanic if injection pumps last as long now as they did ten years ago.  

Waste vegetable oil- post restaurant fryer oil- is the subject of much discussion over the last several years. Used by iteslf, WVO needs to be heated and flushed out of the injection pump after running. Heated tank and switch-over systems exist. I oppose them simply on principle because of the added complexity and plumbing... I prefer to blend my fuels in-tank. Veg oil is generally an excellent lubricant for high pressure, tight tolerance pumps because of the molecular shape and the ability to deform and actually break to absorb the damaging forces of friction and high pressures between moving parts- but only ONCE.  It cannot lubricate once it has been broken and subjected to extreme shear forces.

 The only real drawbacks to vegetable oils are that they can cause gelling in cold weather, and can clog injector tips in high concentrations. Veg oil creates no problems for most diesel engines in a fuel mix with under 30% veg with injector cleaner and cetane boosters added- Since veg oil is a great lubricant- ONCE- it is best removed from service immediately after doing its job. So using veggie oil as lubricant, then burning it right away after is the best way to make good use of leftover foodstuff. I use up to 5% low octane gasoline in my veggie oil to keep it fluid and pumpable in the cold wintertime. Also, because veg oil has a few more BTU's (measure of heat energy) than diesel fuels, so overall economy and output power will increase as well.

  One of the best lubricants for diesel injection systems is one that is intended to be burnt without creating soot and ash, adds a substantial amount of lubricity without alot of extra cost, and won't add smell or smoke to our diesels for the enviro-whiners to complain about. That ideal lubricant is plain and simple 2-stroke oil intended for chainsaws, marine outboard engines and other small high-speed 2-stroke engines. The quality of 2-stroke oil seems to make little difference when used as fuel system lube, so the lower quality and price oils can provide all the lubricity needed when blended to .5% (200:1) There is no need to buy the expensive synthetic oil for this purpose, but there are always some of us (yes, me too) that use the best no matter what, so go for it... 

 I normally burn around 30% waste vegetable oil, about 5% waste engine oil and other lubricants, and the remainder is diesel fuel. Additives totalling about 1% of the total volume of fuel in the tank help lower the viscosity slightly for easier pumping contain cetane boosters for easier starting, and sometimes more volatile solvents like low octane, fresh gasoline, isopropyl alcohol for water removal, and specific diesel additives to help clean injectors, combustion chambers and valves. I usually increase the amount of this additive package when the temps drop to facilitate easier starting in the winter. Sometimes I skip the WVO and WEO for a tank or 2 to clean out the combustion components.  

So basically, if its oil, a diesel engine can burn it without modifications. Check your engine specifics first, but most are good with, and may appreciate, at least some added recycled oil in the fuel supply.

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