Letting an unlicensed freelancer work inside your building
If an uninsured individual spills oil in a basement or damages an engine, every consequence flows to the resident who booked them: the community fine, the cleaning bill, the unrecoverable repair cost. Treat gate registration and management approval as part of the job, not bureaucracy.
Paying without paperwork
A cash payment with no invoice buys an oil change and nothing else: no warranty evidence, no resale history, no recourse. The invoice with company name, TRN, odometer, oil specification and filter part number costs the provider two minutes and is most of what you are paying a legitimate business for.
Upgrading to thicker oil because it is hot
The instinct that 45-degree summers need heavier oil is decades out of date for modern engines, which rely on precise flow through tight clearances and variable valve timing. Going thicker than the manual permits can starve exactly the components the heat threatens; the GCC specification already accounts for the climate.