My engine became shinier.
I did not notice any darkening from the product.
Now my engine might be darker to begin with as it has been exposed at many a show over the last 25 years.
My headlight manual opening knobs have faded to gray from sunlight, so maybe my motor had already darkened more.
Thank you both for your responses.
It's always good to know how things workout!
Have a GREAT Holiday Season!!!
Marty