Temporary non-use of truck
06-07-2018, 12:38 PM
#11
What benefit do you expect from keeping the electronics "warm"? A disconnected battery shouldn't discharge in such a short time period, and aside from losing the usual settings that go away when disconnecting the battery, I don't see any advantage to spending the money on a tender and needing to have shore power. I'm familiar with them, as I have a pair of motorcycles and have needed to recharge my XTerra due to lack of use during the summer, but once I put a negative-disconnect switch on it, I stopped having any issues (well, aside from needing to reset the clock each time I reconnected it).
And why a full tank? With a metal tank and a long period of inactivity, the concern I've always been taught to worry about is that temperature fluctuations lead to condensation and rust. While condensation could still be an issue in a plastic tank, I think you'd be better off minimizing the left-over fuel and adding fresh (ideally before starting up again, but if not, shortly thereafter) to dilute the stale fuel. If I'm missing something, I'd be glad to hear it (between the motorcycles and the truck, I've usually got something sitting for longer than I'd like).
And why a full tank? With a metal tank and a long period of inactivity, the concern I've always been taught to worry about is that temperature fluctuations lead to condensation and rust. While condensation could still be an issue in a plastic tank, I think you'd be better off minimizing the left-over fuel and adding fresh (ideally before starting up again, but if not, shortly thereafter) to dilute the stale fuel. If I'm missing something, I'd be glad to hear it (between the motorcycles and the truck, I've usually got something sitting for longer than I'd like).
06-07-2018, 01:09 PM
#12
I leave for extended periods on a regular basis and my research indicates the following.
- Battery tender. Hotly debated whether it helps or hurts for this period of time. Since we don't know the static battery drain on your truck there is no way to know. On my truck I don't use one and on my bikes I do.
- Full or empty tank. Condensation on tank walls happens from water in the fuel vapor, not from directly separating from the fuel. A full tank lessens this issue. It's not corrosion you are worried about, it's the ruined fuel pump, filter, and injectors from the crap that grows in water in the tank. This issue has killed many an airplane fuel control.
- Pure gas or E-10. Pure gas is less likely to contain water and degrades slower, but we are talking a couple of months vs years.
- Fuel stabilizer. Absolutely.
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CTLimey150 (06-07-2018)
06-07-2018, 01:59 PM
#13
Senior Member
What wasn't mentioned is fuel grade. Lower octane fuels are not as well refined and lose octane rating at a fairly rapid pace. Your 87 octane could very well be at 84 or 85 after sitting for just a month or two. Higher octane fuels are more stable and lose octane at a slower rate. All of them are gradually losing octane over time. For extended period storage, it is best to fill the tank to the top with premium. When used you will have a much greater likelihood of remaining above the 87 octane threshold. If you have a tune, turn it down to an 87 tune until the next fill up.
06-07-2018, 02:12 PM
#14
I have worked in refining and blending of gasoline and other petroleum distillates for over 35 years and this is the first time I have heard that about octane degrading. I do know over time additives by their nature, not having all the same specific gravity will separate in a tank. Ethanol being the biggest culprit. Like anything left long enough gasoline will absorb oxygen or oxidize. If that is what you mean by losing octane then I'm of a like mind. 3 to 4 months with Sta-Bil added, I believe is well within a reasonable period.
06-07-2018, 02:14 PM
#15
Found it. This is taken directly from Sunoco tech literature. It give a great explanation that is relevant to this discussion.
It is necessary to briefly review what octane is in order to dive deeper into stability issues. At fueling stations in the United States, octane is typically displayed as a number, 87 through 93. This number is known as Anti-Knock Index (AKI). AKI is the average of Research octane number (RON) and Motor octane number (MON)(Totten). Essentially, these numbers provide a scale to measure how much heat and pressure can be put on the fuel before it spontaneously combusts. Spontaneous combustion is a source of engine knock which can quickly damage an engine. Octane ratings are important because different engines expose fuel to different amounts of pressure and heat. Engines must use the proper octane fuel to avoid knock and provide reliable operation.
A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.
87 octane fuels tend to be less refined and contain more unstable hydrocarbons. As the months pass during storage these unstable components react to form gums, varnishes and lower octane hydrocarbons. As a result the octane can decrease within months for 87 octane fuels, especially when stored under less than ideal conditions. 93 octane fuels are more refined and contain more stable hydrocarbons. These stable hydrocarbons can last 2-3 times longer than 87 octane fuel. Even in proper storage 87 octane gas can start to degrade in 3 months, 93 octane fuel should last closer to 9 months before degradation is noticeable. Keep in mind that 93 octane fuels are still susceptible to octane loss and vapor pressure decreases due to butane evaporation.
Octane stability in racing fuels is much different because fuel quality is valued more than production cost, unlike the pump gas industry where cost drives the majority of refining decisions. A large part of any quality race fuel is consistency. Race fuels are designed to be high in octane to allow for increased compression ratios and boost levels. In order to achieve high octane and consistent composition, pure chemical components are mixed with highly refined gasoline. The components used in Sunoco race fuels are very stable and can retain octane in excess of 2 years when properly stored. We have test results confirming octane stability in our unleaded, leaded, ethanol-free and ethanol fuels. The butane vapor pressure issue is addressed with the use of chemical components that boil around 80°F. The higher boiling point means vapor pressure decreases won’t be as common until the fuel is exposed to temperatures above 80°F.
Some high octane unleaded fuels, 260 GT Plus, and octane boosters contain the additive MMT. MMT is a very effective octane booster and doesn’t harm oxygen sensors or catalytic converters so, it is ideal for modern vehicles. Please note this additive is degraded by sunlight and can lose all octane boosting properties within minutes of exposure (L.Ter Haar). Degraded MMT will settle to the bottom of the container as a rust colored material that can clog fuel lines and filters. Extra care needs to be used when storing and handling MMT fuels in order to minimize contact with sunlight. The additive is stable in gasoline as long as no UV light hits the fuel. Sunoco 260 GT Plus is our only race fuel that contains MMT.
Octane stability is greatly affected by the storage conditions. Proper storage can preserve octane for years but improper storage can reduce octane and degrade fuel within weeks. That is why we provide proper storage information on our website. Click here to view our storage recommendations. http://www.sunocoracefuels.com/tech-article/race-fuel-storage
Special thanks goes to Minnesota State University Mankato, Automotive Engineering Technology students for suggesting the topic of this article.
Author:
Zachary Santner
Technical Specialist
Sunoco Race Fuels
Octane Stability: High Octane vs Low Octane Fuels
Octane is the most talked about property when it comes to gasoline. It’s no surprise because selecting octane of gasoline is the only choice the consumer has, except what station to buy it from. In this article we will focus on octane stability of 87 and 93 octane pump fuels versus racing fuels and what you can do to prevent octane loss in your fuel.It is necessary to briefly review what octane is in order to dive deeper into stability issues. At fueling stations in the United States, octane is typically displayed as a number, 87 through 93. This number is known as Anti-Knock Index (AKI). AKI is the average of Research octane number (RON) and Motor octane number (MON)(Totten). Essentially, these numbers provide a scale to measure how much heat and pressure can be put on the fuel before it spontaneously combusts. Spontaneous combustion is a source of engine knock which can quickly damage an engine. Octane ratings are important because different engines expose fuel to different amounts of pressure and heat. Engines must use the proper octane fuel to avoid knock and provide reliable operation.
A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.
87 octane fuels tend to be less refined and contain more unstable hydrocarbons. As the months pass during storage these unstable components react to form gums, varnishes and lower octane hydrocarbons. As a result the octane can decrease within months for 87 octane fuels, especially when stored under less than ideal conditions. 93 octane fuels are more refined and contain more stable hydrocarbons. These stable hydrocarbons can last 2-3 times longer than 87 octane fuel. Even in proper storage 87 octane gas can start to degrade in 3 months, 93 octane fuel should last closer to 9 months before degradation is noticeable. Keep in mind that 93 octane fuels are still susceptible to octane loss and vapor pressure decreases due to butane evaporation.
Octane stability in racing fuels is much different because fuel quality is valued more than production cost, unlike the pump gas industry where cost drives the majority of refining decisions. A large part of any quality race fuel is consistency. Race fuels are designed to be high in octane to allow for increased compression ratios and boost levels. In order to achieve high octane and consistent composition, pure chemical components are mixed with highly refined gasoline. The components used in Sunoco race fuels are very stable and can retain octane in excess of 2 years when properly stored. We have test results confirming octane stability in our unleaded, leaded, ethanol-free and ethanol fuels. The butane vapor pressure issue is addressed with the use of chemical components that boil around 80°F. The higher boiling point means vapor pressure decreases won’t be as common until the fuel is exposed to temperatures above 80°F.
Some high octane unleaded fuels, 260 GT Plus, and octane boosters contain the additive MMT. MMT is a very effective octane booster and doesn’t harm oxygen sensors or catalytic converters so, it is ideal for modern vehicles. Please note this additive is degraded by sunlight and can lose all octane boosting properties within minutes of exposure (L.Ter Haar). Degraded MMT will settle to the bottom of the container as a rust colored material that can clog fuel lines and filters. Extra care needs to be used when storing and handling MMT fuels in order to minimize contact with sunlight. The additive is stable in gasoline as long as no UV light hits the fuel. Sunoco 260 GT Plus is our only race fuel that contains MMT.
Octane stability is greatly affected by the storage conditions. Proper storage can preserve octane for years but improper storage can reduce octane and degrade fuel within weeks. That is why we provide proper storage information on our website. Click here to view our storage recommendations. http://www.sunocoracefuels.com/tech-article/race-fuel-storage
Special thanks goes to Minnesota State University Mankato, Automotive Engineering Technology students for suggesting the topic of this article.
Author:
Zachary Santner
Technical Specialist
Sunoco Race Fuels
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CTLimey150 (06-07-2018)
06-07-2018, 02:14 PM
#16
I'm in Ct, and could always swing by to check on things if needed, but since we are in Ct, we do get ethanol in our fuel, so definitely a stabilizer, and full tank. Battery tender should be used as these new vehicles always have a draw from the electronics. If you need a tender to borrow, I have that as well.
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CTLimey150 (06-07-2018)
06-07-2018, 02:34 PM
#17
Senior Member
Sunoco has some excellent info on octane degradation. I was using their fuel for some record attempts (successful!!) and had a pretty lengthy explanation, but I'm certainly no expert. They mentioned two things. One was the difference in the refining of the two and the other was additives and oxygenators. One additive in particular starts degrading in minutes when exposed to UV light.
Fungible gasoline is a byproduct of several streams in the refining process then blended and sent through a refining stream to "homogenize" it so it is consistent. When gasoline is sent to tankage it is analyzed for octane and blended to 85 octane research method. Additives and ethanol are blended in at the tank truck fill before delivery.
I worked on their process instrumentation but I'm hardly a chemical engineer.
Last edited by Wicked ace; 06-07-2018 at 02:36 PM.
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CTLimey150 (06-07-2018)
06-07-2018, 07:51 PM
#18
Put star Brite fuel treatment in it, close the windows, fill the tank, leave a damp rid on the inside, put up a sun shade, and leave it. Guys do it on deployments all the time and they’re fine. Change the oil when you get back.
06-07-2018, 09:00 PM
#19
I wouldn't even worry about fuel stabilizer, quantity in the tank, quality of fuel, etc. The Ford Fusion Energi is a plug in Hybrid that will go 24 miles or so on a charge and then switches over to standard gas/electric hybrid when you use up the initial charge. Ford is aware that some people may never go more than 24 miles between charges, which leaves the fuel sitting in the tank for long periods of time. Because of that, if the gas engine hasn't been started in two years, it locks you out of the electric portion and forces you to burn all of the fuel in the tank. Clearly, Ford feels that whatever gas you happen to get is stable for 2 years in the tank with no additives or other considerations. I don't see 3-4 months being an issue at all.
06-07-2018, 09:56 PM
#20
Old Fart
I have no specific experience with storing a vehicle, but one thing strikes me. If you are concerned about the gas going bad and are thinking of leaving as little amount of gas in the tank as possible, how do you get the vehicle to the gas station to blend in fresh gas on your return, without having to use the supposed bad gas to get it there?