Normally just air, unless you get your tire company to inflate them with nitrogen, which many people claim is better.
Yes.
Inspect the front tires they may have a bubble on one of them it is possible that a wheel bearing is going out but the easy check is to inspect the tires after you have driven it a few miles
Your universal joints are shot, get them replaced asap!
fuel pump is located inside the gas tank.
Radon gas.
It is what fills the tires, in the form of air.
There's moisture in air. When you fill your tires with compressed air, the moisture goes in the tire too. Moisture then has potential to rust out the rim from the inside. They use other gas (nitrogen?) that doesn't have moisture. Usually garages will put green air valve caps on tires filled with gas.
will tires make noise if there choppy on inside
Maybe, the manufacturer optimized the tire size to the vehicle, if your currently running larger than stock tires then you could be decreasing your mileage. Check the inside of your drivers side door for a placard with the correct tire size and inflation.
Tires last longer and work more efficiently when the wear is even. Gas milage improves as well.Rotating the tires will extend the life of the tires.
Nitrogen
Nitrogen.
Nitrogen
It is nitrogen.
Nitrogen, because it is an inert gas.
If you go too big the steering tires will rub inside bodywork.
Drivers need to do everything they can to eek out the best gas mileage possible from their vehicles. Having the right size of wheels and tires, filled to the correct pressure, can make a big difference in the gas mileage a vehicle gets. Most vehicles have this information recorded just inside the drivers side door. This information may also be found in the owner's manual for most vehicles. When shopping for new wheels and tires for a car, be sure to purchase the sizes recommended by the vehicle manufacturer to get the optimal gas mileage the auto is rated for.