6 letter words
USEFUL​9
5 letter words
FUELS​8
FLUES​8
FUSEL​8
4 letter words (12 words)
SELF​7
FUEL​7
FUSE​7
FLUE​7
SULU​4
ULES​4
FLUS​7
ULUS​4
ELFS​7
LUES​4
FEUS​7
SLUE​4
3 letter words (12 words)
USE​3
SUE​3
FLU​6
LEU​3
ELF​6
SEL​3
ELS​3
FES​6
EFS​6
FEU​6
ULU​3
ULE​3
2 letter words (5 words)
US​2
EL​2
ES​2
FE​5
EF​5