Maybe a little WD40, Lithium grease, Vaseline, nose oil, or just about any lubricant applied sparingly would be better than nothing. Yeah, my 9880 used to make those left-side squeeks, too. Does Jiffy Lube do 9900's?
What I learned in my forays into industrial design is that the properties of lubricants and other manufacturing consumables are often more geared to the requirements of the automated machinery dispensing them, rather than to the end device itself which generally has much wider tolerances.