Whats the rule/benefit of using oil in a marinade?
IE. always/almost always use it? Never use it, use it sometimes, etc.
I've not seen much commentary on the chemistry of marinades. They don't penetrate very far, even in long marinade times, only about 1/4 inch.
Cook's Illustrated has in a few instances minimized acid and maximized oil to not change or denature the meat. I think that's an interesting approach but would like to see a clearer break down of which flavors are more oil soluble than water/acid soluble and vice versa to really reap the benefits.
I've tended lately to a sort of disassembled (not deconstructed) sort of marinade. I'll usually build a light rub and season the meat. Then I'll sprinkle the meat with some cider vinegar or citrus or wine and let it sit 10 or 15 minutes. Then cook with some brushed on oil. I picked up this approach watching Daisy Martinez a few years ago where she'd season a pork chop or steak with adobo and vinegar. It's fit well with my cooking style and I've liked the results.
Injection is something I've liked better than marinading but I've not done much with it. BDL has some good injection experience.
My favorite marinade.
juice of one lemon--occasionally also the zest as the mood strikes
2-3 cloves garlic, minced
1/2 cup dry white wine or less sweet fruit juices
1/3 cup olive oil
3 tablespoons dijon mustard
black pepper to taste
Any single herb like basil, thyme, oregano, rosemary, or sage can be added as well, but the marinade works well without an herb as well.
I like how apple juice works with the mustard for pork or chicken.