Being that the oil filter and rear shaft lube are so easy to change, experiment a little to see which one you like best. I bought a case of Honda Full Synthetic 10-30 and K&N motorcycle oil filters. Using them now until gone. Not to sure about 10-30 down in sunny Florida. Will change to Full Synthetic 10-40 by Mobil 1 for motorcycles or Valvoline 10-40 for motorcycles as it is readily available at Wally World. Filter wise, I would stick with the OEM Honda, K&N or HiFlow. And yes, there is a difference in motorcycle oil filters from automotive oil filters. Fortunately it really doesn’t matter as the GL1800 only revs to 6k rpm.