Ford Full-Size Cars 1968-1988 Repair Guide

Fuel and Engine Oil Recommendations



Depending on the year produced, your car may be equipped with a catalytic converter as a part of its emission control system, necessitating the use of unleaded gasoline. Using leaded fuel will damage the catalytic converter, resulting in poor vehicle performance and excessive exhaust emissions.

If the engine in your car is designed to function on unleaded fuel, use gasoline with a minimum octane rating of 87, which in most areas means regular unleaded gasoline. Always use a high quality fuel containing detergent additives, to keep fuel injectors and intake valves clean.

If the engine occasionally knocks lightly under acceleration, or when going up a hill, do not be concerned. However, if the engine knocks heavily under all driving conditions, or knocks lightly at cruising speeds, try switching to another brand or higher grade of gasoline. If knocking persists, the cause should be investigated or serious engine damage could result.


See Figure 1

Always use a high quality detergent motor oil. To determine an oil's quality and viscosity, look for the American Petroleum Institute (API) symbol on the oil container label. Always use an oil with an API classification "SG" or higher.

For maximum fuel economy, look for an oil that carries the words "Energy Conserving II" in the API symbol. This means that the oil contains friction reducing additives that help reduce the amount of fuel burned to overcome engine friction.

The Society of Automotive Engineers (SAE) viscosity rating indicates an oil's ability to flow at a given temperature. The number designation indicates the thickness or "weight" of the oil. An SAE 5 weight oil is a thin, light oil; it allows the engine to crank over easily even when it is very cold, and quickly provides lubrication for all parts of the engine. However, as the engine temperature increases, the 5 weight oil becomes too thin, resulting in metal-to-metal contact and damage to internal engine parts. A heavier SAE 50 weight oil can lubricate and protect internal engine parts even under extremely high operating temperatures, but would not be able to flow quickly enough to provide internal engine protection during cold weather start-up, one of the most critical periods for lubrication protection in an engine.

The answer to the temperature extremes problem is the multi-grade or multi-viscosity oil. Multi-viscosity oils carry multiple number designations, such as SAE 10W-40 or SAE 20W-50 (the "W" in the designation stands for winter). A 10W-40 oil has the flow characteristics of the thin 10 weight oil in cold weather, providing rapid lubrication and allowing easy engine cranking. When the engine warms up, the oil acts like a straight 40 weight oil, providing internal engine protection under higher temperatures.

Ford Motor Company recommends using either SAE 5W-30 or SAE 10W-30 oil. SAE 5W-30 should be used if you anticipate the ambient temperature in which you'll be driving to fall below 0°deg;F (-18°deg;C) but not go higher than 100°deg;F (38°deg;C) during the period before your next oil change. SAE 10W-30 should be used if you anticipate the temperature in which you'll be driving to be between 0°deg;F (-18°deg;C) and 100°deg;F (38°deg;C) and above, during the period before your next oil change.

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Fig. Fig. 1: An example of the API Symbol