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Even though this article was written almost 10 years ago, it's content remains unchanged except that government regulations have allowed (in some cases mandated) reformulated fuels contain up to 15% alcohol and that has resulted in a huge increase in service issues directly related to these fuels. In short, older fuel systems were never designed for this level of concentration, and water saturation of these fuels has become an ongoing issue in our service schedule. Read the following article if you have time, if you don't, use only PREMIUM fuel in your boat (as it does not containe alcohols) and keep your tank FULL during the off season. Read on for the full scoop: RFG is simply an environmentally friendlier version of gas. In a nutshell, RFG is gas that has been supplemented with fuel oxygenates (alcohols such as ethanol and methanol). Most components found in conventional gasoline are made up of hydrogen and carbon (hydrocarbons). Oxygenates are made up of hydrogen, carbon, and oxygen, and therefore add oxygen to the fuel air mixture (hence the term oxygenates). It is these oxygenates that help turn harmful carbon monoxide emissions into harmless carbon dioxide. In fact, oxygenates actually chemically lean out the fuel/air ratio (rather than mechanically through jetting). Since these oxygenates lean out the mixture, they enhance combustion and therefore reduce emissions. Since alcohol also raises the octane level, they can contribute to a better running engine if a previously used fuel did not meet the minimum octane requirements for that particular engine. I should point out at this time that OCTANE DOES NOT BOOST POWER. It simply allows your engine to reach the performance that it was designed to operate at. Using a higher octane fuel than your engine requires will do nothing to increase performance. So what's the difference between ethanol and methanol? Ethanol is a grain based alcohol and methanol is ether based. There are two types ether based RFG's -- Methyl Tertiary Butyl Ether (MTBE) and Ethyl Tertiary Butyl Ether (ETBE). While both ethanol and methanol are alcohols, methanol is more sensitive to water than ethanol. Methanol is also not as compatible with engine fuel systems as ethanol and thus you can't use as high a concentration. Also, RFG's have a considerably shorter shelf life than conventional gasoline (90 days is considered the practical limit). This means that if you are using this fuel and leave your boat unused for prolonged periods, you will have to add stabilizers during the boating season. It also means you must keep your tank topped up because of condensation problems associated with these fuels (discussed later). It is also important to know that alcohol is a *solvent* and as such acts as a detergent in your fuel system. While this sounds just like what the doctor ordered, it means that using this fuel for the first time will likely result in filters repeatedly plugging up as dirt and gum are dissolved from the boats fuel tank and lines. Since I have already warned of potential water problems associated with this fuel, it's wise to ensure that new water separating fuel filters are installed prior to it being used and that these filters be inspected and changed regularly. In older boats, and system of parallel filters is recommended. Now for my personal opinion of these fuels....Why don't we want alcohol based fuels in our boats? For starters, the last thing we want to do is lean out the air/fuel mixture in our engines. Marine engines are finely tuned high performance beasts that already test the limits of their endurance doing what we ask of them. To add a further uncertainty of too lean a mixture is pure suicide (especially in outboards). Also, as previously stated, alcohol attracts and holds moisture. This is great if you want to remove water from your car's fuel tank but not so great when you think about where we use our boats - around water. This trapped water will corrode any steel fuel tanks/lines/fittings in your boat which may result in a fire hazard. Furthermore, depending on how much alcohol is present in the gas, the amount of water it holds may be too much for the engine to burn without experiencing negative side effects (rough idle, hard starting, high speed missing etc). Aside from the water problems, the alcohol itself presents a problem in that it attacks rubber and some kinds of gasket materials (remember, it is a solvent). Again, this is a safety issue in that it can lead to an on board fire, but it also becomes a maintenance issue if you have to start replacing the aforementioned parts. Here's something that you won't hear discussed much about RFG's: they have less BTU's than conventional gas. To the layman, it means you will probably experience a small loss in power while using these fuels. Engines with on board ignition/fuel management systems (Current EFI models) will likely automatically compensate by increasing the fuel volume or retarding the timing (since the fuel itself will burn leaner and the on-board systems will identify and correct this condition) and you will likely burn slightly more fuel as well. For example, if you used to cruise at 3000 RPM and travel at 25 mph, when using RFG's you might find that you had to increase the throttle setting a small amount to achieve the same result with a RFG. Although I have seen no definitive study supporting this, I suspect that the increase in fuel economy and decreased emissions that cars experience with RFG's will be unseen in boats because the increased quantity of fuel required to maintain performance levels will erase the reduced pollutants linearly (eg. when we advance the throttle to compensate for the power loss, the increased emission resulting from the higher throttle setting will negate the benefits of the oxygenated fuel). Here's something else to think about -- MTBE is also a dangerous pollutant and it's now turning up in California resevoirs used to store drinking water. It seems in our zeal to rid the planet of one pollutant (lead), we've simply replaced it with another. In my opinion, stay away from ALL alcohol blended fuels and octane boosters. Buy a minimum octane of 89 from a reputable dealer and get back to trouble free boating. When you get right down to it, why on earth would anyone buy (sometimes) cheaper blended fuels to save a few cents per gallon when the ultimate saving at the end of the summer will be pocket change? Factor in the added grief these products may cost you in the long run and good ole' high test is lookin' mighty inexpensive. ;-) Happy boatin' Dave Brown Brown's Marina Ltd. |
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Brown's Marina Ltd.
1641 Chaffey's Lock Road
Elgin, Ontario, K0G 1E0 CANADA
Tel: 1-800-561-3137 (toll free)
Tel: 1-613-359-5466 - Fax: 1-613-359-6376
Comments: send me email: dave@brownsmarina.com