Stay away from AC Delco they are just STP oil filters with a different drainback valve.
Old AC delcos WERE a great filter.... now...FAIL

For starters, when looking for a good filter, take the time in the parts stores and look at the filter pleat (the folds back and forth on the media) stack up (how bunched up).
The perforated internal sleeve (Best is metal) holes and flow design
Anti drainback valve (silicone)
Perforations on top of filter
These are just some quick easy "eyeball" comparos to do when looking.
Me, I like WIX (NAPA filtersare made by wix), WIX has a racing series also, Baldwin, Hastings and Bosch. (Not in order of superiority)
Never tried K&N, but feel as they are just a lil to pricey and you are paying for the name...JMHO.
Would like to take a look at the new Royal Purple Filters, havent had a chance to peep them yet.
I wasnt impressed with Amsoil filters for the price. Overpriced hype like the oil IMO. Yeah yeah Im sure this will ruffle feathers.:biggrin: