1995 Dodge Caravan SE stalls

My dad has a 1995 Dodge Caravan SE. It stalls whenever he drives it. When stop for a while, it will start again. This became a headache because it
happens everytime he drove by, specially on a busy street. He noticed an "oil" light in the information center whenever it stalls.
So, my dad went to Chrysller dealer and have it check with a mechanic. They diagnosed it and said the problem was an air flow and a thermostat. It costs him $350 including labor.
The mechanic also suggested that fuel pump has to be change soon. My dad didn't bother thinking of the fuel pump repair because it will cost him a lot of money.
We thought it will be fine now because its fix.....unfortunately it stalled again. He brought it back to the dealer and told what happened. The mechanic again diagnosed his van. They suggested its the fuel pump needs repair. So, why didn't figure it out on the first place? That way, my dad won't to pay double of the cost. My dad suggested since they didn't fix his van, he should have a discount for the next repair. And so they did, 10% off repair cost. It costs him $850 including labor. Hopefully, the problem will fix.
After a few days of driving, my dad had a peace of mind. It stalled again! My dad was very upset and so do we. Stress and frustration. Now, me and my brother kept thinking what was going on with my dad's van.
Could it be an engine oil? My dad uses 5W30 regular oil and change every 3-months. We lived in a place with lots of winter. It could go -32C in here too. Our record was -50C last year's winter. He use regular oil during winter not synthetic oil. Is it worth to use synthetic oil instead, regardless of seasons?
I always used Mobil 1 Synthetic Oil 5W30 to my 1998 Chevrolet Malibu 3.1 V6 LE and change it every 3-months on all seasons. I never had any oil problems yet and improved my gas mileage too.
Maybe my dad needs an oil change and stick with one brand.
Any suggestions?
Thanks
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a rusty wire caused me what you tell.
oil pressure light comes on if the engine rpm drops too low like it happens as the engine stalls. It is ok and check the oil level as the car runs fine.
AL wrote:

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