I will probably get a bunch of flak for this but I have always driven the car to get it good and hot first...I buy any spray engine cleaner from the local parts store or Wmart..usually store brand....take the car to the local car wash....pop the hood and spray away. Let it set a few minutes and then hit it with the high pressure wand. I have been doing this for almost 20 years with absolutely no issues ever. I spray everything......and I mean everything. I have never had any electrical issues, mechanical issues or chemical issues with aluminum parts.