Hi. I've had my oil on my 2003 Galant changed at several places including the dealer and I've noticed two different oil filter sizes. My question then is dealer filter better than OEM? Why aren't they the same sizes?

its not the entire size of the filter but the way the gasket size.you know the black rubber that makes the seal.one filter can be fat and big another can be skinny and small.but if the top part are the same then it fits perfect as well.i have used two different size but always make sure the thread size is the same.i ususally buy the k&n filter or the mobil 1 those are better then the dealers IMO.

save some thought time and just buy a bunch from the dealer. ITs the OEM part made by mitsuibishi. Sometimes you buy a filter in the store and it doesnt have the anti-backflow valve in it that is in the OEM filter. So you can look for that on aftermarket filters as well.