i dont drive our croosfire a whole lot either 1,000 to 1,500 miles a year here lately ! FSS lets me go 2 yrs before it time to change generally around 1,500 mile mark & two yrs ! I never had any sludge issues so it must be your short trips ! We only drive ours in warm weather & it sleep all winter ! but when we do drive it we go on lots of long trips too !