I have an older but excellent Remington 11-48 in 28 gauge from the early sixties that jams up on me when the temperature dips below 30 or so degrees. Is there anything I can do? I keep it fairly well oiled during the season. Should I not be oiling it as much? Or is there a brand of oil that's better for lower temperatures?
I was say as always give the shotgun a good cleaning. I don't use oil. I use grease. Specifically Birchwood Casey RIG. No odor and is a rust preventive. Brownells did a test with several Firearms specific oils and greases and the Birchwood Casey Rig outperformed them all.
The running joke in my dad's shop is that the gun sounds like its a quart low on oil. Over oiling can cause a lot of problems and the most frequent is jamming in cold weather as the viscosity increases. It can really be bad with hunting guns because other materials from the field can get in the oil and cause problems.
When lubricating a gun, make sure there is only a very thin film on the gun. I prefer a Teflon based oil such as Tri-flow or Rem-oil but there are so many out there that will work now. I usually don't use any more than will fit on a 1" by 1" patch and don't directly squirt oil in the action put squirt it on the patch and use the residual in the plastic applicator to get in the moving parts.
I'd start out taking the gun completely apart and cleaning off all oil with denatured alcohol. It should fix your problem.