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Mink Islander · 08-16-2006, 01:16 PM

First, I will admit, I am no expert on this topic, haven't had a chemistry class since high school, but I have been Googling around since my old Whaler has a fiberglass tank (until this weekend!). I haven't seen anything that says that the typical plastic tanks are affected by the ethanol blend, but there are a number of sources saying that fiberglass tanks -- especially older ones, are made with resins that break down when exposed to ethanol and therefore can do serious damage to your engine. For $200, I think it's worth switching to a plastic tank, no?

On the subject of fuel stability, I've attached this interesting link:

http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf

The crux of the memo is that your biggest risk with an ethanol blend is phase separation (now I'm really going over my head), where the ethanol separates from the gasoline. That can happen when (a lot) of water gets introduced into the gas. Ethanol is infinitely soluble in water and water is heavier than gasoline -- consequence: the water can pull the ethanol out of the gas and sink to the bottom where your fuel line then draws in not water (which would just stall the engine), but an ethanol enriched water mix that can seriously damage the engine (very lean, negatively rx's with oil lubricants in the engine etc). According to this memo, such phase separation requires a relatively high amount of water in the gas -- more than what typical condensation or humidity might contribute.

I've seen commentary elsewhere that the ethanol will separate over time on its own. Not sure that's the case, but I'm sure someone out there has knowledge (or at least an opinion!) about that.

Didn't read anything the states that the "shelf life" is less for an ethanol blend than the MTBE gas but could well be the case. It really sounds like the moral to the story is to be very sure you don't let a lot of water get into your gas. My thought is the marinas should be doing a brisk business in installing water separators between the tank and engine.

Now the petro chemists can correct any errors I've made....

08-16-2006, 01:16 PM	#4
Mink Islander Senior Member Join Date: Apr 2004 Posts: 753 Thanks: 59 Thanked 271 Times in 129 Posts	EPA Ethanol Study First, I will admit, I am no expert on this topic, haven't had a chemistry class since high school, but I have been Googling around since my old Whaler has a fiberglass tank (until this weekend!). I haven't seen anything that says that the typical plastic tanks are affected by the ethanol blend, but there are a number of sources saying that fiberglass tanks -- especially older ones, are made with resins that break down when exposed to ethanol and therefore can do serious damage to your engine. For $200, I think it's worth switching to a plastic tank, no? On the subject of fuel stability, I've attached this interesting link: http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf The crux of the memo is that your biggest risk with an ethanol blend is phase separation (now I'm really going over my head), where the ethanol separates from the gasoline. That can happen when (a lot) of water gets introduced into the gas. Ethanol is infinitely soluble in water and water is heavier than gasoline -- consequence: the water can pull the ethanol out of the gas and sink to the bottom where your fuel line then draws in not water (which would just stall the engine), but an ethanol enriched water mix that can seriously damage the engine (very lean, negatively rx's with oil lubricants in the engine etc). According to this memo, such phase separation requires a relatively high amount of water in the gas -- more than what typical condensation or humidity might contribute. I've seen commentary elsewhere that the ethanol will separate over time on its own. Not sure that's the case, but I'm sure someone out there has knowledge (or at least an opinion!) about that. Didn't read anything the states that the "shelf life" is less for an ethanol blend than the MTBE gas but could well be the case. It really sounds like the moral to the story is to be very sure you don't let a lot of water get into your gas. My thought is the marinas should be doing a brisk business in installing water separators between the tank and engine. Now the petro chemists can correct any errors I've made....