With the vast array of oils available and the endless hype by auto manufactures and oil companies it is difficult to know what to do and when to do it.
Let's start with some of the misleading hype from many auto manufactures. Many of them tell you that you should use 5w / 30 or similar oil and change every 7000 miles.

Let's look at the numbers first. To better understand the viscosity number of oil you can think of the oil as marbles. A little marble, # 5 will fit into a thin opening between two objects and if you move the two objects in opposite directions the # 5 marbles will roll and keep the two surfaces from rubbing each other.

Now if you took all the # 5 marbles out and installed just # 30 large marbles. They would be too large to fit between the two surfaces and the surfaces would rub again each other and quickly destroy the surfaces ( IN SECONDS!!!). Now suppose you have two surfaces that have enough clearance to accept a # 30 marble and the two surfaces will roll the # 30 marbles just fine. Now you remove the # 30 marbles and install just # 5 marbles. If the two surfaces move close to each other they will contact the # 5 marbles and roll OK but, the two surfaces have a lot of room to move.

This movement can allow the two surfaces to crash into each other, thus squeezing out the # 5 marbles and allowing the two surfaces to rub and self distruct. Thus, a multi grade oil like 5w30 or 10w40 will meet the standards of a wide range of  clearances. However, that is not the whole story.
Temperature is a major factor in this. Viscosity tries to decrease as temperature increases. Meaning, a  #30 marble when too hot will become a # 5 or less. The ability of an oil to maintain it's viscosity as temperature increases is called it's viscosity index. Penn. crude oil has a naturally high viscosity index meaning it will try to keep it's viscosity when hot. Chemicals and treatments can boost the viscosity index of an oil. STP is a brand of a viscosity index booster among others.  An engine that can use 5w30 oil will need to raise the viscosity numbers as it ages.

The 6000 to 7000 mile oil change is not a savings for the car owner. Not in the long run. You are saving a few pennies by  not changing the oil but it IS costing you engine wear, UNNECESSARY ENGINE WEAR. It's not that oil wears out, it's the that oil gets contaminated as it is in a continuous process of being distilled and diluted by fuel and countless chemicals in the gas and in the oil. Even though you may get away with a 7000 mile oil change at first, you won't get away with it long.

Always change the filter when you change oil.

Do's and Don'ts

Do change oil and filter every 3000 to 4000 miles under normal driving conditions.

Do use factory recommended oil and filters while in warranty.

Do raise the viscosity number in hot climates and lower the number in very cold climate conditions.

Do warm the engine up at a fast idle in cold climate conditions before driving.

Do keep your crankcase vent system checked. It can have a effect on your lubrication system.

Don't ever add a different brand of oil to oil in your engine unless you are sure you are going to change
oil and filter in a day or so.

Don't think you can drive to the nearest service station or even the next exit if your oil light comes on
while driving. Major damage starts within seconds of when the light comes on.

Don't buy a brand of oil or filter Just because it is cheaper.

Don't buy a brand of oil or filter Just because it is the most expensive. Do at least a little research.

Don't disable any emission control devices in an effort to gain horse power. The main reason is that
you will NOT gain any horse power by disabling any emission control device.

Flushing Your Radiator

Most people ensure that their vehicles have clean oil and good brakes. Not many ever think  about the cooling system, at least not until something goes wrong with it. What can go wrong? Plenty: an engine generates enough heat to destroy itself. The cooling system protects against damage, keeping the engine operating within the correct temperature range. The radiator is a major part of that cooling system, and it needs a flushing (a deep internal cleaning) at least once every two years.

Flushing removes rust and sludge in the radiator, and cleans blocked water channels which cause overheating. Is it hard to flush a radiator? It's much easier than writing a check to the local garage for repairs you might have avoided. It's also much easier  than sitting at the side of the road watching steam  rise from under the car hood and feeling a bit hot under the collar yourself.

NECESSARY INGREDIENTS

1. 1-2 gallons (4-8 liters) of antifreeze

3. A garden hose with a nozzle and a water supply4

Be sure the engine is cold!

A  Place a drain pan under the radiator drain tap (at the bottom of the rad)

B: Remove the radiator cap and the pressure cap at the overflow bottle. 

4. Inspect the radiator pressure cap for defects in the rubber or spring.

5: Inspect the clamps and the hoses for leaks..(for tell-tale drops of coolant). 

6:  Drain the radiator by opening the lower stop cock valve.

7: Rinse the radiator by running clear hose water through it until it runs clean.

8: You can now mix your coolant mixture with distilled water as indicated on the coolant container. 

9. Add the coolant mixture to the radiator.

Flushing Your Radiator and Engine (Better)

1. Best done outside on your driveway. 

2. After doing the radiator flush above, remove the engine's thermostat and the lower radiator hose at the radiator. 

3. Run your water hose continually filling from the lower radiator hose and flush (as long as 30 minutes) until the water runs clear. 

4. Now place the hose in the thermostat hole and run in reverse flow until the water runs clear. 

5. Replace thermostat, hoses.

6. Fill the radiator with a coolant mixture.

7. Replace radiator and coolant overflow caps.