I would recommend testing it in a portable generator, $600-1,200, before putting it in my $25k car. Of course you could give it as an anonymous gift to someone at work with a card:
Congratulations!
You have been chosen to test this advanced fuel additive for free if you will simply test it with two tanks of gas (see enclosed gas card.) All you have to do is run one tank without the additive and record the total miles and then run a second tank with the additive and report the results when we call you in 30 days ...
Yes, it is a cruel world.
Bob Wilson