As for the GDP of these countries,
Iran, Indonesia, Saudi Arabia, United Arab Emirates, Iraq, Qatar, and Kuwait
rank 11th, 17th, 19th, 31st, 48th, 53rd, 57th in GDP.
Afghanistan, which is not part of OPEC, but is a Middle East country, had a GDP of 20 billion, which would’ve placed it 2nd.
So there are 3, potentially 4, in the top 20 GDP.
https://www.populationu.com/gen/countries-by-gdp
And as I said, the impact of what vehicles run on is negligible since all that will change is how the fuel is processed.