You can safely round down to 5 quarts. In cars that call for odd amounts like that, I tend to round a bit. Like 901Memphis said, as long as it's between the Low/Full marks (or just a hair over), it'll be fine. For instance, on my Firebird it calls for 4.6 quarts, but I put in 4.5. My mom's old 2003 Malibu used to call for 4.6 also, and I'd use 5 quarts when using an oversized filter. If I used the regular sized filter, I'd use 4.5 quarts or so. I may end up doing the same in the Firebird if I continue to use oversized filters on it. It would usually bring it up to just a little bit above the full mark.