Fig. 1. Effect of number of sequential oil applications on total soluble solids (TSS) in ‘Chardonnay’ berries at harvest in 2001 and 2002. Pooled data are shown because an F-test indicated that results from 2001 and 2002 were not significantly different.

Image from Plant Health Progress article:
Use of Petroleum Derived Spray Oils in Washington Grapevine Powdery Mildew Management Programs