I confess to being super-cynical. Indeed, I am a professional cynic.
'Testimonials' like this one off their site always make me nervous.

"Just as you stated 'that after running Auto-rx® in my car it would become
more efficient', and it has. After running well over 200 miles after the test,
and I am now on my second full tank of gas, I have noticed an increase that
went from 18 miles per gallon to 21 miles per gallon.. I am glad to say that
the product has done everything you said it would."

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1986 300E 5-Speed 240k mi.