Engine oil with added sand?

I saw this billboard this afternoon and it got me thinking. Quartz (silicon dioxide) is the second most common compound on earth. It also forms the bulk of what we commonly refer to as sand.

I'm certainly not a car guy and don't know my way around and engine. (However, I am a proud bike geek.) If you'll pardon me for being a bit pedantic, isn't sand in your engine a bad thing? And if that is the case, isn't this a rather poor name for a motor oil. Yes, quartz does have an enviable hardness, 7 on the Mohs scale. But is hardness really a desirable characteristic in a motor oil.

This type of branding, and the accompanying advertising, will only work if the average consumer has a shockingly low level of scientific literacy. And that is a pretty shocking indictment of the education system.

Source for packaging photo: http://shop.citroenclassics.co.uk/index.asp?function=PRODUCTIMAGEWINDOW&closedelay=20000&SRC=http://shop.citroenclassics.co.uk/ekmps/shops/citroenclassics/images/total-quartz-5000-15w-40-petrol-engine-oil-5-litres-347-p[ekm]277x300[ekm].jpg