There may be difference in the engine running

I think engines or by the ignition timing etc. all react a little differently or not at all on some additives. I drive a Honda with 2,4l suction motor and have found that: engine runs really quietly and especially "soft". Also, I think he pulls a little better - but that may be my imagination. No less consumption. With STP additive I have, for example, can detect a difference with my vacuum cleaner. Additional additives are luxury, but now and then I'm doing it to me.