10W30 conventional vs. 5W30 blend

Jan 7, 2021
Should I use 10W30 conventional (Castrol GTX) or 5W30 synthetic blend (Pennzoil) in my '99 Dodge Caravan (2.4L 4-cyl, 100k miles, drive it about 3k miles/yr, near New York City, rarely gets colder than 20F in winter). Bought the car new and always used 5W30 conventional (Mobil, Pennzoil) but now seems that is no longer available. My concern with synthetic blend is that it might cause engine problems, vs. the 10W30 which might cause the oil pump to work harder at startup.
(Same question for my '02 Toyota Corolla, 1.6L 4-cyl, 100k miles and 3k miles/yr, also bought new and always used 5W30 conventional.)
It seems Castrol GTX is the only 10W30 which is truly conventional (per their website); is that correct?
Pennzoil yellow bottle 5w30 is still available. Why do you think it’s not?

Pennzoil yellow bottle 5w30 is still available. Why do you think it’s not?

The 5w30 pennzoil says "Synthetic blend" on the bottle (on that web page, and in the store too).
Since SN, all of the 5w30 conventionals were really blends. Supertech says conventional on the bottle, it's a blend. Valvoline says blend on the bottle, used to say conventional, when they changed the bottle people posting to Amazon got ticked off cause it wasn't real oil. If it's SN+ or SP it's got close to fifty percent group III no matter what they call it.
Lots of very good and very inexpensive 5w30 oils out there -- these are all labeled as syn blends except Supertech which is likely to be a syn blend as well:

Chevron Supreme 5w30, $12.42 for 5 quart jug -- this would be my choice for you, OP.
Castrol GTX 5w30 ultraclean, $16.97 for 5 quart jug
Supertech 5w30, $13.47 for 5 quarts
Quaker State advanced durability 5w30, $14.67 for 5 quarts
Valvoline daily protection 5w30, $16.97 for 5 quarts
Pennzoil yellow bottle 5w30, $17.97 for 5 quarts
etc etc.
Contrary to popular belief at BITOG, engine does not know if the oil is conventional, blend or synthetic.
All it needs is a lubrication oil.
Right, it’s the oil that knows if you put it in the wrong vehicle …
I don't know why you would want all conventional but Valvoline Daily Protection is still labeled conventional in 10w30, since the 5w30 is a blend I think that would mean the 10w30 is all group 2. I have no idea why that would be better but if it meets specs....
The camshaft and other rotating components get confused when they see a syn oil molecule and then a conventional one comes along then another syn.

They are like "this is wacked; what is going on?"
But I keep hearing on here that today's synthetic is not synthetic and is only "highly refined" dino oil.
True. There seems to be more threads here about conventional lately. Not sure why. A synthetic or synthetic blend is not going to ruin a engine.

OR the labeling stayed the same, the oil changed, and people didn't even know it!