Best underside cleaner

[70 Top Banana]

I recently purchased another car. Original paint, interior and drivetrain and I am going to try and leave it that way. That being said I would like  to clean up the underside of the car as best as I can. It is undercoated and has road dirt and grime, tar etc.. the usual stuff you would find, plus it was stored for several years so, cob webs spider sacks etc.

I have used degreasers, just good old soapy water, oven cleaner ( that may have been what killed the grass off the driveway). I also have a good power washer. Any recommendations that might do a better job and not be too harsh?
Thanks!

[Rdchallenger]

I recently purchased another car. Original paint, interior and drivetrain and I am going to try and leave it that way. That being said I would like  to clean up the underside of the car as best as I can. It is undercoated and has road dirt and grime, tar etc.. the usual stuff you would find, plus it was stored for several years so, cob webs spider sacks etc.

I have used degreasers, just good old soapy water, oven cleaner ( that may have been what killed the grass off the driveway). I also have a good power washer. Any recommendations that might do a better job and not be too harsh?
Thanks!

Try this?

https://www.amazon.com/Undercarriage-Pressure-Carriage-Attachment-Underbody/dp/B0854557S6/ref=asc_df_B0854557S6/?tag=hyprod-20&linkCode=df0&hvadid=416617970121&hvpos=&hvnetw=g&hvrand=1814844320441928630&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9007942&hvtargid=pla-898477664055&psc=1&tag=&ref=&adgrpid=94717458420&hvpone=&hvptwo=&hvadid=416617970121&hvpos=&hvnetw=g&hvrand=1814844320441928630&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9007942&hvtargid=pla-898477664055

[1 Wild R/T]

Grab a garden sprayer & a gallon of Castrol Super Clean.... Have the pressure washer ready to go.... Soak the underside of the car with Super Clean, try to re-wet it keeping it wet for about ten minutes, then get after it with a pressure washer.. The worst areas may need a second application....

[anlauto]

Steam cleaner

[70 Top Banana]

Castrol super clean- terrific idea and the pressure washer attachment a great idea as well. Thanks!