Tokyo auto shops and Detroit car dealerships have been running short of motor oil, paint and other products for months since the Middle East conflict snarled global supply chains.

Now, while a potential deal between the U.S. and Iran may bring an end to the fighting, industry experts and executives say it is unlikely to deliver immediate relief to the smaller shops that have been squeezed by Tehran¡¯s shutdown of the Strait of Hormuz.

Closure of the strait has blocked almost a fifth of global oil flows and led to bottlenecks for some petroleum-derived products.