Can you use a smaller diameter spare wheel?
The short answer is yes. If you think about it, space saver spare wheels frequently have a smaller diameter than regular wheels. For emergencies, using a smaller wheel to get you home or to a tyre repairer is fine. via
Should you use a spare tire cover?
Without proper protection, your spare tire will be exposed to a lot of hot sun that you just can't avoid. After a period of time, this exposure can damage your tire by causing cracks in the sidewall and weakening the rubber. It makes your spare tire less structurally sound. via
Are most spare tires universal?
Each spare tire differs in size and weight and is specific to its vehicle's model. Differences in size, weight, and lug-nut positions make spare tires only suitable for the intended vehicle. They are not interchangeable or universal. via
Can you use a donut from another car?
The short answer is 'NO'. A donut spare tire can not be safely interchanged between vehicles. Tire Rack only recommends interchanging donut spare tires with the exact same make and model of car. Donut or compact spare tires are specifically designed for the vehicles that they are paired with. via