5W-30 or 5W-40: reading the grade debate through a Gulf windscreen
The commonest technical argument at a UAE oil change is grade. The number before the W describes cold-flow behaviour, nearly irrelevant where a cold start means 28 degrees. The second number is the one that matters, because it describes viscosity at operating temperature, and Gulf engines live at full temperature in 45-degree air, idling in traffic with the air-conditioning compressor loading them.
Where 5W-40 earns its keep is in older, high-mileage engines with worn clearances, where the thicker film helps oil pressure and curbs consumption. A competent technician asks about mileage and any oil-burning history before recommending anything; one who reaches for the same drum regardless of what you drive is telling you how the rest of the job will go.