Tim ...
Great job.
Doesn't need many changes at all, perhaps a few more links to wiki pages where they first appear on your page and just a change of the link format.
For links within the wiki you only need to use double square brackets. The http bit is for links outside the wiki and adds a little symbol after the link. General format is to capitalise the first letter of a page, but for a link, the wiki software ignores this format. So [[methanol]] will automatically link to the Methanol page.
If the text you want to be a link differs from the page name to which you intend to link, you can link thus "... assumes you have a GL eco reactor or similar ..." would be written "... assumes you have a [[GL Processor|GL eco reactor]] or similar ..."
Agree about the photos, they always pep up the page and make it more interesting.
Perhaps another addition could be a table of several washes describing the condition of the oil and a before and after titration value, so people can see the full benefit of the process.
There is also a funny quirk with the indexing on the main page ... once a new page is added to the wiki, it's necessary to go into edit mode on the main page and click save without altering anything, to force the software to list the new page. I've already done this so it now appears in the main page menu.
Too late now but I'm happy to make the changes tomorrow, unless someone else beats me to it!
Look forward to your next page, we've all slowed down a little recently and welcome the help!