The most typical reason is a blown head gasket(s).
motor oil
The manufacturer of the 1995 Honda Accord recommends 10W-30 weight motor oil. A heavier motor oil can be used in extreme climates.
According to the 2003 Ford Focus Owner Guide ( North America ) ( 5W-20 )
Oil in the radiator is usually an indication of a leaky head gasket.
Usually you get oil in your radiator when you blow a head gasket and oil leaks into your radiator. Blown intake gasket is also possible, as well as a hole in the engine's water jacket (very uncommon). Also, if the vehicle's transmission cooler coil is internal to the radiator, a leak from it may be possible (most tranny coolers are external for this reason).
Consult the owners manual for that info.
Motorcraft is the OEM Ford motor oil brand.
You need to have the radiator flushed immediately
Gasoline or oil usually goes into a motor.
With engine oil filter change ( 5.0 quarts / 4.7 liters of engine oil )
5-20 per Ford spec. All seasons.
Blown headgasket, failed oil cooler, etc.
your oil cooler is leaking
Head Gasket
any kind of oily oil will work. open the hood and put some in the engin and the radiator to keep it well lubricated.
The motor oil drain plug is located on the motor oil pan.
The Ford motor company recommends you use 10W-30 weight motor oil in the 1998 Ford F1 50 truck. A heavier weight motor oil can be used in extreme climates.