I recently did my oil change and I'll like to share with you what you should be looking for when you take you new/used/old care to a mechanic.

Disclaimer:

Do not attempt to do any of this on your own it could result in severe damage or even loss of life

The ride is a 2000 Jeep GC Limted 4.7l
Due for oil change and having problem with oil pressure gage dropping to zero at startup.
Sign of bad oil sender (common in this model), or  more serious  issue such as bad oil pump, worn bearing, or clogged pick up screen.
Running engine with no bad vibes suggests no oil starvation(normally would have to confirm pressure with a gage), so I had to change sender.

First run engine till warm then put vehicle on a ramp(normally change while on level ground), and choke rear wheels.

Open oil filler cap to vent system while draining.
Get appropriate socket wrench to loosen drain plug
Then carefully drain oil pan.

After oil is drained use appropriate filter wrench/hand to remove filter.
Let it drain, then wipe the surface clean with a lint free wipe.

Lubricate rubber gasket on oil filter with some oil , and add some iol to filter to prime it.

In my case I will have to replace my oil sender first.
Sender is connected to wire on top of filter adapter,

Pic shows new(with locktite on thread) and old sender.

Screw on the new oil filter till snug, the tighten by 1/2 turn more.
Make sure everything that was opened is closed.
Then fill oil filler (might be on valve cover or seperate fill tube), with recommended volume, grade and weight.

For Nigeria it will be 10w 30 for most cars, but check your owners manual to confirm

Current API grade is SM

For more information, read these links

http://www.motoroildealer.com/motor_oil_rate_gas.htm
http://www.bobistheoilguy.com/

If you have to spend a million on your car, make sure the mechanic is doing it right, and using the right stuff. Every 3 months/5000km, both oil and filter has to be changed or you may as well hava burnt the money you spent on the car.

Check the color of a clean oil, do not use recycled oils.
Then look around underneath for any sign of damage.
I found one of my CV boot torn(not too bad) this causes the clicking sound you hear when a car turns
Apart from that everything else looked normal for a truck with 130,000 miles.

It was cold when I did this, so I was in no mood to go further.
Reset maintenance schedule, check oil level and I'm good to go for next 3500 miles.
I do 70% highway driving, naija traffic is severe condition frequent stops.

Do not go cheap on this, it is the main reason most have issues within months of their new car.

Breaking in the craftman tool box for a oil change before a long 12 hour road trip