is it better to drive in 3rd gear rather than drive with an automatic?

The motor and trans are designed to work fine in Drive. You will have better throttle response in 3rd, and get way worse gas mileage.

The overdrive in those trucks will allow the converter to lock and unlock in overdrive as necessary. And if you are going below 40 MPH, it will most likely be in 3rd, or 4th with the converter unlocked. This will have the same effect as driving in 3rd.

Especially since it is a truck, and they are meant to tow, they have sufficient cooling systems in place fo the trans fluid. The fluid will get hot from the converter slipping, but it is normal.

Leave the car in drive unless you are towing. When towing it will drop down frequently into 3rd or second to get the vehicle moving, and the constant in and out of overdrive will generate significant heat in the tranny.

Personally, i would rather drive manual. I own a manual car some may call me a bit bias, but I'm sure drivers with automatic would feel the same about their car. Yes driving an automatic is much easier, but driving a manual is more fun, at least in my opinion. To get back to your question. In order to start a manual car you would have to press the clutch all the way down (the pedal farthest to the left) and turn on the ignition. I drive in the city of Chicago and some might say it is horrible to drive with a manual, but in reality it is'nt that bad. Driving a manual you would have to press the clutch every time you would switch gears, (the gears allow you to move at a higher mph) and i assure you it really is not that complicated as it sounds. Maybe look up a couple videos on you-tube to get a better idea. I hope this helped in a way.

I can see no advantage to leaving your automatic transmission in third gear, while probable disadvantages are poor fuel economy and more rapid wear of the engine and drive-train components.

Read your owners manual and follow the directions you find there. As Chief just said, your engine and transmission are designed to work together, and there is no need for you shift an automatic transmission manually. Just leave it in drive, and let the transmission do the job it was designed to do.

Your friend is absolutely correct. Drive, or OVER-Drive is for straight highway only. If your doing local driving, driving on hills, stop and go, or speeds less then 35-40mph then leave it in "3".

If you look in your owners manual, it will state exactly what I said above.