I was wondering about this same question recently. The last car I owned I would clean the engine bay every couple of months and even though the car was 15 years old, when I got my Z and sold it, everyone was always amazed at how clean it was under the hood. Now I did sometimes get corroded electrical connections,and probably prematurely burnt out some altenators. The Z has much better sealed connecters than my old car did. Something I did at the DIY car wash was to do the "no spot rinse" of the engine at the end. This water had been de-ionized at the car wash I used so I was less likely to get corrosion. I will probably start using this no spot rinse on my engine bay just to remove the road dust from the engine.