One thing I use on my car is Marine Grade grease on the front suspension as it’s well exposed to water. It’s relatively expensive at £17.00 at my local yacht chandlers (less on ebay http://www.ebay.co.uk/itm/QUICKSILVER-Extreme-Marine-Grease-Mercury-Mercruiser-92-8M0071841/161178256628?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3Dc842599edc44430686d7f76f4262a5fc%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D261422415848&rt=nc however a tube has lasted over 2 years now and as it doesn’t break down with water, should help keep those ball joints good for years to come.