Yes pump E85 can be an issue depending on where you live, just like pump gasoline the blend changes summer to winter, and folks with bleeding edge tunes can have problems if the take a car tuned on summer blend E85 and run it on winter blend E85. For those folks there are two options. You can buy performance E85 in drums or cans which has a known blend, or buy straight E98 and blend your own custom blend.
Our local drag strip fuel farm sells straight E98. The other option is to buy summer blend from a station you trust in drum quantities during the summer before the winter blend switch and store it over the winter. If you go to the station owner you can usually find out exactly what blend they have in the tank by having them check their delivery tickets, or using a hydrometer to check the specific gravity, or doing a "water test" yourself.
Water test: mix a small amount of E85 with a known quantity of pure water and that will force the gasoline component to settle out if you use enough water. Then you can subtract that gasoline content from the original fuel volume to figure out the gasoline/ethanol ratio.
E85 and nitrous work very well together!
E85 fuel ethanol content seasonal changes
E85 fuel blends change content seasonally just like all gasolines blends change with the seasons. This seasonal change in blend for E85 is primarily to improve cold weather starting, where the changes in gasoline during cold weather is to improve cold weather starting. In the summer months, gasoline must be blended to reduce vapor lock and to reduce evaporative emissions.
The recommended dates for changing E85 fuel blends are listed in a chart in the E85 handbook on page 33-34, which is in the "E85 Fuel Specification" tab.
The Volatility class specifications are broken down on page 10.
Volatility class 1 --- minimum ethanol 79%
Volatility class 2 --- minimum ethanol 74%
Volatility class 3 --- minimum ethanol 70%
As you can see each region has a different start date and recommendation for seasonal blends depending on local weather climate.
Here on the high plains east of the rockies in Colorado we run the class 1 fuel blend from mid June -- mid Sept, run class 2 fuel from mid Sept -- mid Oct and run the class 3 fuel blend from Mid Oct -- mid April, then back to the class 2 blend from mid April to mid June. The standard only specifies a minimum ethanol content, vendors can run higher ethanol content if it is economical. If it is cheaper for the fuel blender to add more he can. Ethanol content is bottom line driven by local weather conditions, and cold starting problems for local drivers just a gasoline blends are modified to give easier starting in cold weather.
In the Southern part of Texas they would never go to a class 3 blend, and in Wisconsin, they would only have the class 1 blend for about 2 months in the summer. In Florida they would be on class 1 almost all year long and in North Dakota and Wyoming and Montana, they would be on class 3 almost all year long.
Testing ethanol content with the water test
The proper way to do the water test is specified on page 38 of the handbook.
Handbook method:
http://www.afdc.energy.gov/uploads/publication/ethanol_handbook.pdf2.1 + 1.94 x (total vol - lower meniscus) = hydrocarbon
ethanol = 100 - hydrocarbon
Ethanol bonds very strongly with water so the percentage is not a direct relationship as seen above in the formula.
For example, If you add 10 ml of water to 100 ml of standard pump gasoline, and end up with 17ml of phase separation -- you have a full E10. (yes I know the math does not work but this is due to ethanol's bonding properties) In this case 10 ml of water and 10 ml of alcohol bond to form a mixture of 17 ml of water alcohol mix.