You can use it full strength or diluted. I would start diluted first. Really depends on the mission and how bad your vinyl is. To really take advantage, get a nice soft bristle scrub brush to get its full cleaning power. The brush is just as big of a key as the cleaner.
As mentioned just make sure to use a good conditioner/protectant after the fact.
2000 X-Star, 3000lbs ballast, LTR 330, Acme 1235 14.5X14.25prop.