Biofuels

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Changes In Gasoline IV: A detailed resource to understand the past and present properties of Spark Ignition Engine Fuel

Ethanol and Gasoline Blends in Small Engines: Oklahoma State University Extension

Ethanol and Small Nonroad Engines: Kansas State University Extension

Ethanol and Water Contamination — Comparing Off-the-Shelf Water Removal Additives

Ethanol will mix with water and thus gasoline ethanol blends can hold some water. This is of particular concern for small engines and engines which are used intermittently due to water contamination during storage. We set out to answer two questions.

How much water can E10, and E15 gasoline ethanol blends hold in solution?
Can off the shelf fuel additives increase the amount of water held in solution?

Results

Water held in gasoline ethanol blends
FUEL	Water Held in Solution
E - 0	Zero teaspoons per gallon
E -10	3.06 teaspoons per gallon
E - 15	6.47 teaspoons per gallon

Fuel Additives Claiming to Remove Water
Additive	Water Held in Solution
STP	No increase in water holding
BG - Ethanol Fuel System Drier	Increased water holding by 0.23 tsp per gallon
Iso-HEET	Increased water holding by 0.23 tsp per gallon
Stabil - Ethanol Treatment	No increase in water holding
Rislene	No increase in water holding
HEET	Partial Effect: Solution was more clear but phase separated layer remained. we tested water additions in 0.01% increments
Seafoam	No increase in water holding
Valvoline - Nitro Shot	No increase in water holding

Conclusions

Unlike pure gasoline ethanol blends can hold small amounts of water in solution which is then run through the engine harmlessly. In pure gasoline small amounts may build up in the tank.
Only 2 of 8 fuel additives tested increased the amount of water held in solution. All claimed on their label to "remove water", "solve phase separation", "dry the fuel" etc

Our Recommendations

Use fresh fuel. Use within 30 days of purchase is best.
Store lawn mower and other small engines empty in a dry place (if not empty then store them completely full to minimize air space). Fuel additives for fuel stabilization are recommended by many manufacturers. This study did not test these other properties of the additives.
Large amount of water contamination in a fuel tank is likely equally bad for E-0 or an ethanol blend. Avoid water contamination by covering small engines or storing them in a shed or garage.