Ricky Racer has a good point, and it looks like this topic has been well covered on this site already.
As with most things in life, moderation is key when cleaning aluminum with SG. The aircraft grade has a corosion inhibitor that allows you to soak parts for longer periods. If you just want to toss an aluminum part in the washer, scrub it off, rinse and dry, you'd be fine with the standard stuff. If you soak aluminum for days it will turn dark/black at the least (trust me on this). By the way, I do not own stock or work for these guys. Here is some info from their website:
"Aluminum - Is it safe to use Simple Green® on aluminum?
When used with caution and according to the instructions, Simple Green All-Purpose Cleaner has been safely and successfully used to clean aluminum. Simple Green All-Purpose Cleaner, Crystal Simple Green® Cleaner/Degreaser, Simple Green Pressure Washer Concentrates, and Pro Series™ Simple Green® Automotive Cleaner have been used on aircraft, automotive, industrial and consumer aluminum items for over 20 years. However, caution and common sense must be used: aluminum is a soft metal that easily corrodes with unprotected exposure to water. The aqueous-base and alkalinity of Simple Green All-Purpose Cleaner can accelerate the corrosion process. Therefore, contact times for unprotected or unpainted aluminum surfaces should be kept as brief as the job will allow - never for more than 10 minutes. Large cleaning jobs should be conducted in smaller-area stages to achieve lower contact time. Rinsing after cleaning should always be extremely thorough - paying special attention to flush out cracks and crevices to remove all Simple Green® product residues. Unfinished, uncoated or unpainted aluminum cleaned with Simple Green products should receive some sort of protectant after cleaning to prevent oxidation.
Simple Green has also developed break-through water based cleaners that are safe for use on metals, plastics, rubber and high tech alloys. Extreme Simple Green® Aircraft & Precision Cleaner and Simple Green® Pro HD are available on both the industrial and retail markets, respectively. These products were initially developed for the aircraft industry and extensive testing shows that they are safe and effective on a variety of metals and other sensitive surfaces even in the most extreme circumstances. "
Simple Green® Stainless Steel One Step Cleaner & Polish is another option for cleaning polished aluminum. This product is designed for light duty metal cleaning and polishing.