The secret is google.
type in your search phrase in google search engine, and in addition type in this phrase:
The internal search engine will not find anything if you only type in 3 characters, like "oil".
Try this in Google, exactly as: mgb oil site:bobistheoilguy.com
This gets me 19 pages of results, so you may need to adjust the terms before the "site:bobistheoilguy.com" as desired until you get the results you want.
I've found that Google beats most Web-boards' internal search functions.