Recently bought an 88 rx7 and it needs some tlc. While trying to figure out where the drips were coming from under the car, I found a good amount of oil residue on the cooler and crud on the rad. It almost looks like a bunch of mud that's been caked on there for years.

Anyways I gently rubbed the fins with a shop towell to see how bad it is and the fins were starting to bend.

I'm hesitant to use a pressure washer or even a garden hose if softly "dusting" it off causes the fins to close up.
Anyone have success with degreasers?

I read the other threads on this, and I don't want to take it off to be serviced since I need the car nearly everyday.

 

I would start with the garden hose. I wash mine out every year to keep crud from accumulating. A degreaser might help. Try simple green or maybe Gunk foamy engine clean.

 

Brake Clean Will be your bestest friend!

 

I like Castrol Super Clean. The first cleaning, use it straight up. Spray it on, let it it sit, then rinse off. For the next cleaning, 30% super clean in warm water and a stiff bristle brush.