Type of oil for a 2.3

[MRausch82]

What oil would be best for a 2.3 n/a. 15 years ago, when I was driving my Capri daily, I ran 10w40 or 20w50 oils, mainly Castrol GTX. I know the Zinc levels have been lower with the "newer" oils. I was thinking of a 15w40 diesel oil or 15w50 Mobil 1. Thoughts appreciated.

[gr79]

I have two 2.3 engines to maintain and depend upon to be ready to go anytime.
1993 2.3 in a Ranger
1979 2.3T in a Mustang

Both long term 20+ years second owner (me) vehicles. Have databases on everything going into them.
FL-1A oil filters. Nothing else.
Changes at 5000 miles or 1 year with new filter.
Important to check oil every time hood is up and add oil if one or oops 1.5 quarts down.

Owners manual shows recommended grades, change interval, for that year's engines.

Have used regular, semi and full syn grade. Reg, High Mile, Valv Racing, even Valv Next Gen.
Never used Shell, Pennzoil, Castrol or anything not graded S_ by API label.
Same multi grade 30w's year round whether below zero or 100 out.
People i know successfully use Rotella brand even in race engine. I guess its ok.

Ranger- stock 2.3 EFI (roller cam)- Valvoline semi synthetic. Exclusively after the odometer hit 5000 miles.
5w30 is the recommended weight and have stuck to it. Regular semi syn or High Mile. Whatever is on sale.
No leaks, noise. Uses 1-2 quarts per 5000 miles. Over 200,000 on it. Never has been apart.

Mustang- stock 2.3T (slider cam) has had about every brand except dollar store oil in it.
Current load is 10w30 Defy. Top offs with Motorcraft, QS, Warren, or Valvoline.
Rebuilt once 15 years ago. No unusual engine noise.
10w30 semi syn mostly. 10-20w50 is too thick, even if Mobil 1. 10w40 not used.
Does burn oil. Smokes when idling then clears up once rolling.
Valve seals? (common after 75-100k), or turbo (bad rebuild?), both, plus nature of the beast i guess.
Not bad but not good. Has never used less than 1qt/1000 since 1980 at 25k.
At the time, SF oil was top grade and sticker in owners manual stated no CC oil.
Seeps a little from oil pan gasket. VC gasket (Felpro PermaDry) is dry.

[webestang]

I use nothing but FL-1A filters and standard Valvoline 5W-30 every 3000 miles in my 85 2.3L......everything is perfect. Full synthetic is a waste of money.

[ethangsmith]

I've used 5W30, 10W30, 10W40, and 15W40 in the Capri and it seems to like the 5W30 and 10W30 the most. I've used quite a few different brands, but I settled on the Valvoline High Mileage since it's inexpensive and I don't drive the car often.