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Winter fuel vs. Summer Fuel
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colbysmith



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PostPosted: Wed Jan 28, 2015 9:48 am    Post subject: Winter fuel vs. Summer Fuel Reply with quote

I'm sitting here trying to decide if I want to pull my boat out of storage now and fill the tanks, or just leave it until summer. I can buy non-ethanol premium fuel at Kwik Trip now for $2.15/gallon. I expect gas costs are going to start heading back up real soon. Since I put my boat away empty, my savings would be on 40 gals of fuel. However, I'm also aware that winter and summer gas is formulated differently. Although I will more than likely fill the tanks before end of May anyway, so assuming I will probably still be putting a winter blend in. Other than that, any engineers out there that would advise against filling the tanks full now with premium gas that supposedly does not have ethanol, (or course I'll also add marine stabilizer as well), while the prices are relatively cheap? I"ve heard all the arguments back and forth about storing full or empty, and I've done it both ways, so not looking for more argument on that, but rather winter blend vs. summer blend. Colby
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AstoriaDave



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PostPosted: Wed Jan 28, 2015 10:41 am    Post subject: Reply with quote

Not an engineer. Will a longtime organic chemist do?

Winter blend has more volatiles for easier vaporization when the engine is cold on startup. Won't hurt a thing to run it in the summer. You might smell a little bit more fuel odor, but nothing to worry about.

Add the usual stabilizer. The fuel will still varnish up if you don't. The ethanol absence will boost the energy content of the fuel, likely increasing power at the top end a little.

You win on price and power.

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BrentB



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PostPosted: Wed Jan 28, 2015 10:47 am    Post subject: Reply with quote

I am not an engineer and here is m2cw

We have 20 different blends of gasoline to met various and some over lapping state and federal regulations.

from Popular Mechanics article
The reason for the different grades of gas comes down to trying to control VOCs (volatile organic compounds) that are more likely to evaporate the hotter it gets. More VOCs equal more smog, especially in summer, when the heat in the atmosphere increases the propensity for atmospheric ozone and adding in the VOCs increases the intensity of the smog.

The different grades of gas are measured on a system of RVP, or Reid Vapor Pressure, which is measured in pounds per square inch (PSI). The higher the RVP number of a particular gas blend, the easier it is to vaporize and the worse it is for the environment. All gasoline blends have to be below 14.7 PSI, which is normal average atmospheric pressure. Any number higher than that and gasoline would become a gas.

During the summer heat, the RVP of gas has to be especially low to keep it from boiling off. The EPA mandates an RVP maximum of anywhere between 9.0 PSI and 7.8 PSI for summer-grade fuel, depending on region (though you get a fudge factor of 1 psi for using gas blended with 10 percent ethanol). There are even lower RVP-rated fuels for cities like Houston, New York, and L.A. Different states and cities have their own rules based upon their seasonal temperatures—Washington state needs different summer gas than, say, Florida. That’s why there are so many blends. To make it more complicated, the time for switching from summer- to winter-blend gasoline varies by state too.

Generally, the lower the RVP of a gas blend, the more it costs. For example, in winter you can blend butane, which is relatively plentiful and cheap, with gasoline. But butane, which has an RVP of 52 on its own, can’t be used in summer, when it would immediately boil off as a gas. So "purer" summer gasoline is by default costlier. (And there are other factors at play too. More people travel in summer during peak driving season, for instance, putting more stress on demand.)

Back to California’s woes: First, an August fire at a Chevron refinery diminished the ability of the oil industry to meet demand, driving up delivery times and transportation costs. That especially hurts in California, which has stricter standards than anywhere else in the nation as far as what blends it will sell, making the state especially vulnerable to supply issues.

So Brown’s loosening of the rules on gas blends is an attempt to fight back against that vulnerability and bring prices back down. But there’s no guarantee. Gasoline is a commodity, and yet the price-setting system has only a loose relationship to supply and demand. Rather than having an independent governing body oversee the supply side of the equation, suppliers voluntarily report on the supply of oil. And any time the numbers could be fudged for profit, we ought to raise our eyebrows.

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colbysmith



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PostPosted: Wed Jan 28, 2015 10:49 am    Post subject: Reply with quote

THanks Dave. Your title is probably better. I've been reading about the VOC's. Wife tired of my pondering and just said just go get it. So guess I"m out of here. I'll be happy then when I see the prices go up and can say, well at least I saved some.... Smile Colby (And just saw your post pop up too Brent. Thanks.)
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AstoriaDave



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PostPosted: Wed Jan 28, 2015 12:10 pm    Post subject: Reply with quote

Many thanks to Brent for the authoritative dope on summer versus winter blends.

It stuns me that butane is part of any blend. Stuff is a gas at room temp; liquid n-butane boils at 31 F, and liquid iso-butane boils at 11 F. The former is no doubt what is added to gasoline (cheaper, about same energy content, somewhat lower octane).

Either would distill out of fuel at a pretty good rate at 60 F, faster at 80 F. OTOH, both would provide good vaporization on a cold start when it is a cold morning!
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BrentB



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PostPosted: Wed Jan 28, 2015 12:24 pm    Post subject: Reply with quote

EPA regulations

http://www.epa.gov/otaq/fuels/gasolinefuels/rfg/regulations.htm
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BrentB



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PostPosted: Wed Jan 28, 2015 12:47 pm    Post subject: Reply with quote

A Primer on Gasoline Blending
Refining,blending,Emission,fuel,gasoline

Posted on June 30, 2009, 20:38

Refineries produce a more expensive fuel blend during the summer to cut down on smog during hot months. Stations nationwide will start selling a less-expensive winter fuel usually by mid September, which on average means that winter gasoline is less expensive than summer gasoline.

Gasoline is composed of many different hydrocarbons. Crude oil enters a refinery, and is processed through various units before being blended into gasoline. A refinery may have a fluid catalytic cracker (FCC), an alkylate unit, and a reformer, each of which produces gasoline blending components. Alkylate gasoline, for example, is valuable because it has a very high octane, and can be used to produce high-octane (and higher value) blends. Light straight run gasoline is the least processed stream. It is cheap to produce, but it has a low octane. The person specifying the gasoline blends has to mix all of the components together to meet the product specifications.

There are two very important (although not the only) specifications that need to be met for each gasoline blend. The gasoline needs to have the proper octane, and it needs to have the proper Reid vapor pressure, or RVP. While the octane of a particular grade is constant throughout the year, the RVP spec changes as cooler weather sets in.

The RVP is the vapor pressure of the gasoline blend when the temperature is 100 degrees F. Normal atmospheric pressure varies, but is usually around 14.7 lbs per square inch (psi). Atmospheric pressure is caused by the weight of the air over our heads. If a liquid has a vapor pressure of greater than local atmospheric pressure, that liquid boils. For example, when you heat a pot of water, the vapor pressure increases until it reaches atmospheric pressure. At that point, the water begins to boil.

In the summer, when temperatures can exceed 100 degrees F in many locations, it is important that the RVP of gasoline is well below 14.7. Otherwise, it can pressure up your gas tanks and gas cans, and it can boil in open containers. Gas that is boiled off ends up in the atmosphere, and contributes to air pollution. Therefore, the EPA has declared that summer gasoline blends may not exceed 7.8 psi in some locations, and 9.0 psi in others.

A typical summer gasoline blend might consist of 40% FCC gas, 25% straight run gas, 15% alkylate, 18% reformate, and 2% butane. The RVP of the gasoline blend depends on how much of each component is in the blend, and what the RVP is of each component. Butane is a relatively inexpensive ingredient in gasoline, but it has the highest vapor pressure at around 52 psi.

In a gasoline blend, each component contributes a fraction to the overall RVP. In the case of butane, if there is 10% butane in the blend, it will contribute around 5.2 psi (10% of 52 psi) to the overall blend. (In reality, it is slightly more complicated than this, because some components interact with each other which can affect the expected RVP). This means that in the summer, the butane fraction must be very low in the gasoline, or the overall RVP of the blend will be too high. That is the primary difference between winter and summer gasoline blends.

Winter gasoline blends are phased in as the weather gets cooler. September 15th is the date of the first increase in RVP, and in some areas the allowed RVP eventually increases to 15 psi. This has two implications for gasoline prices every fall. First, as noted, butane is a cheaper blending component than most of the other ingredients. That makes fall and winter gasoline cheaper to produce. But butane is also abundant, so that means that gasoline supplies effectively increase as the RVP requirement increases. These factors normally combine each year to reduce gasoline prices in the fall. The RVP is stepped back down to summer levels starting in the spring, and this usually causes prices to increase.

RBOB is the base gasoline mixture produced by refiners or blenders that is shipped to terminals, where ethanol is then added to create the finished ethanol-blended RFG. Gasoline is more volatile than diesel oil, Jet-A or kerosene, not only because of the base constituents, but because of the additives that are put into it. The final control of volatility is often achieved by blending with butane. The Reid Vapor Pressure (RVP) test is used to measure the volatility of gasoline. The desired volatility depends on the ambient temperature: in hotter climates, gasoline components of higher molecular weight and thus lower volatility are used. In cold climates, too little volatility results in cars failing to start. In hot climates, excessive volatility results in what is known as “vapor lock” where combustion fails to occur, because the liquid fuel has changed to a gaseous fuel in the fuel lines, rendering the fuel pump ineffective and starving the engine of fuel. (This effect mainly applies to engine-mounted fuel pumps; a fuel pump located in the fuel tank, as in most modern automobiles, is much more resistant to vapor lock.)

In the United States, volatility is regulated in large urban centers to reduce the emission of unburned hydrocarbons. In large cities, so-called reformulated gasoline that is less prone to evaporation, among other properties, is required. In Australia summer petrol volatility limits are set by State Governments and vary between capital cities. Most countries simply have a summer, winter and perhaps intermediate limit.

Volatility standards may be relaxed (allowing more gasoline components into the atmosphere) during emergency anticipated gasoline shortages. For example, on 31 August 2005 in response to Hurricane Katrina, the United States permitted the sale of non-reformulated gasoline in some urban areas, which effectively permitted an early switch from summer to winter-grade gasoline. As mandated by EPA administrator Stephen L. Johnson, this “fuel waiver” was made effective through 15 September 2005. Though relaxed volatility standards may increase the atmospheric concentration of volatile organic compounds in warm weather, higher volatility gasoline effectively increases a nation’s gasoline supply because the amount of butane in the gasoline pool is allowed to increase.

Besides lowering the volatility of the fuel, other means of controlling the emission of unburned hydrocarbons, for environmental concerns, exist and are exercised. All vehicles sold in the United States (since at least the 1980s, probably the 1970s or earlier) are required to have a fuel evaporative control system (called an EVAP system in automotive jargon) which collects expanding fuel vapor from the fuel tank in a charcoal-lined canister while the engine is stopped and then releases the collected vapors (through a “purge valve”) into the engine intake for burning when the engine is running (usually only after it has reached normal operating temperature.) The fuel evaporative control system is also required to include a special filling cap which seals the fueling inlet to prevent vapors from escaping directly from the tank through it. Modern vehicles with OBD-II emissions control systems will turn on the MIL (Malfunction Indicator Light, a.k.a. “check engine” light) if it is detected that the gas cap is missing or loose and so not sealing. (The general purpose of this light is to indicate when any of the emissions controls are not working properly.)

Oxygenate blending adds oxygen to the fuel in oxygen-bearing compounds such as MTBE, ETBE and ethanol, and so reduces the amount of carbon monoxide and unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending is mandated by EPA regulations to reduce smog and other airborne pollutants. For example, in Southern California, fuel must contain 2% oxygen by weight, resulting in a mixture of 5.6% ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline. The federal requirement that RFG contain oxygen was dropped May 6, 2006 because the industry had developed VOC-controlled RFG that did not need additional oxygen.

MTBE use has been phased out due to concerns over potential contamination of ground water. A common ethanol-gasoline mix of 10% ethanol mixed with gasoline is called gasohol or E10, and an ethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85.
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colbysmith



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PostPosted: Wed Jan 28, 2015 1:20 pm    Post subject: Reply with quote

I've read a lot of stuff this morning, just googling it all. Was hoping for a layman's answer like, don't put the winter fuel in your tank, as it won't run worth a damn in late spring and it has more ethanol and crap in it from the refinery; or fill er up, it's no worse or better than what you'll be buying in late June... Confused But I guess it sort of sounds like that second one. Smile IN any case, just went and put 40 gals in of premium Kwik Trip gas, advertised as having no ethanol, at $2.59/gal. (Earlier thought it was 2.15, but that was their midgrade.) Also dumped in the appropriate amount of Marine Stabilizer! I'm thinking we've seen gas as low priced as it's going to be. In any case, I'd probably be filling up in April or May anyway, and from what I've read it doesn't sound like the summer formulation is out yet then anyway! Colby
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AstoriaDave



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PostPosted: Wed Jan 28, 2015 3:47 pm    Post subject: Reply with quote

More good info, Brent. My takeaway from this one re winter versus summer gas is that the increased butane in winter fuel would not be a serious issue unless the fuel tank or gas can approaches 100 F ... and as a bonus, I now know why winter gas is cheaper!
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BrentB



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PostPosted: Wed Jan 28, 2015 4:08 pm    Post subject: Reply with quote

colbysmith wrote:
I've read a lot of stuff this morning, just googling it all. Was hoping for a layman's answer like, don't put the winter fuel in your tank, as it won't run worth a damn in late spring and it has more ethanol and crap in it from the refinery; or fill er up, it's no worse or better than what you'll be buying in late June... Confused But I guess it sort of sounds like that second one. Smile IN any case, just went and put 40 gals in of premium Kwik Trip gas, advertised as having no ethanol, at $2.59/gal. (Earlier thought it was 2.15, but that was their midgrade.) Also dumped in the appropriate amount of Marine Stabilizer! I'm thinking we've seen gas as low priced as it's going to be. In any case, I'd probably be filling up in April or May anyway, and from what I've read it doesn't sound like the summer formulation is out yet then anyway! Colby


here is another article for storing
https://www.mda.state.mn.us/news/publications/renewable/storinggas.pdf

discussing
weathering
moisture
oxidation
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colbysmith



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PostPosted: Wed Jan 28, 2015 5:36 pm    Post subject: Reply with quote

Good article, thanks Brent! I've followed most of that advice in winterizing (and summerizing my winter toys)... Smile Colby
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thataway



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PostPosted: Wed Jan 28, 2015 8:37 pm    Post subject: Reply with quote

Perhaps this is a little off topic. But I would rather have fresh gas in the tank. I realize that you have looked at, and done both full and empty tanks. I used to have full tanks. I go for empty tanks (even pumped fuel out). Some of this is because I have a carburated engine. Yes stabilizer makes fuel still usable. However, fresh fuel (without water, and which has come from a high volume dealer) is going to be better running in the long run. Probably fuel costs will go up. But is the few cents worth the difference?
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colbysmith



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PostPosted: Wed Jan 28, 2015 10:12 pm    Post subject: Reply with quote

I hear you Bob. One of the reasons that I tend to store my boat with empty tanks over the winter. Beside, you never know how long that fuel has already been sitting in the station tank. But reasonable savings matters also. I know 40 gallons isn't a lot, but all depends on how much fuel prices go back up. Cool Now I'm not a fuel hoarder, so haven't gone out and bought extra gas cans or anything. But figure it can't hurt to go ahead and fill the boat up now, rather than in a few more months. Smile Every little bit does help, and I don't think it will cause any problems that cost more. Neutral Colby
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hardee



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PostPosted: Wed Jan 28, 2015 10:33 pm    Post subject: Reply with quote

Colby, Hope you got them filled today. Just heard on the news, so of course we know it is true, gas prices are going up. Barrel prices went up today, it was on the news tonight so we know the price at the pump will be up tomorrow. Cry

I filled the motorcycle last Monday after my last trip, Didn't fill the pickup but it was only at half. Another trip on the bike tomorrow ('cause it gets 60+ mpg) because it won't be rainy.

BTW, I store the boat with full tanks, Marine Stabil and Startron. Never a hiccup on the start, even after a 5 month stand, one time, and usually 3-short 4 month. This year, no more storage, Already have 5 days on the water in January.

Harvey
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Byrdman



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PostPosted: Thu Jan 29, 2015 5:21 am    Post subject: Reply with quote

Colby: Another fix is keep heading south. Our water in TN is soft with bubbles and we have some 50 degree weather lined up. Come on down for a visit! A one day run each way!
Brent: Good read man...but toss me a picture or two in there please. Mr. Green Beer

Good read and informative. Thanks!

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