Help getting out encrusted dirt

[SATracker]

I'm working on a 2006, white, Toyota Highlander, never been detailed. The best I can describe it, there's some baked on dirt that has collected over the years. I'm using ONR for the car wash; on one section I tried Stoner's "Tarminator"- nothing, another section responded to Meguiar's 105 on an orange pad but some spots are hard to get to. The two pictures attached are in the hood & engine bay. That dirt will not wash off, wipe off, or come off with 105 on a cloth. Thoughts?

[Flash Gordon]

Wash it with a mixture of Dawn and Castrol Super Clean/Purple Power :dblthumb2:

[C. Charles Hahn]

I'd hit that with Optimum Power Clean or P21S TAW and a brush, personally.

[JonMiles]

I'd hit that with Optimum Power Clean or P21S TAW and a brush, personally.

:iagree: OPC is strong enough to break down most crud with no problem. A little agitation and dwelling of the product will loosen it up. May need to be clayed to finish the job 100%

[Perfections]

Tooth brush + apc :)