From past experience, the fuel system cleaners that contained PEA had a distinct "rotten fish" odor. This includes Redline SI-1, Gumout Regane HM, and Amsoil PI (IIRC).
I have never used the old formula Techron which was supposed to have a higher PEA content. However, I did pour one bottle of the new formula Techron into a friend's car today and noticed that the Techron did not have any "rotten fish" smell whatsoever. The liquid had a very light petroleum solvent smell.
Obviously, this is not a scientific test, but my understanding is that the Amines are what give the fuel system cleaner the "rotten fish" smell.
I have never used the old formula Techron which was supposed to have a higher PEA content. However, I did pour one bottle of the new formula Techron into a friend's car today and noticed that the Techron did not have any "rotten fish" smell whatsoever. The liquid had a very light petroleum solvent smell.
Obviously, this is not a scientific test, but my understanding is that the Amines are what give the fuel system cleaner the "rotten fish" smell.