Contact
Email is the way to reach the site: hello@mpgtoliters.com. Messages are read by the person who runs the site, and a reply usually comes within a few days.
Corrections are the most useful thing to send. If a conversion looks wrong, say which page and which value, and what you expected instead. If a fact in a guide is out of date or unsourced, say which one. Errors are fixed and the page's updated date is changed.
Suggestions for new converters or value pages are welcome too. Requests to add MPGe, or to convert between units of different kinds, will get a polite explanation of why not; the about page has the reasoning.
There is no form on this page because a form would mean sending what you type to a server, and the site's whole approach is that it does not do that. Your own email client is the form.