See Figures 1, 2 and 3OIL
The Society of Automotive Engineers (SAE) grade number indicates the viscosity of the engine oil and thus its ability to lubricate at a given temperature. The lower the SAE grade number, the lighter the oil; the lower the viscosity, the easier it is to crank the engine in cold weather.
Oil viscosities should be chosen from those oils recommended for the lowest anticipated temperatures during the oil change interval.
Multi-viscosity oils (10W-30, 20W-50, etc.) offer the important advantage of being adaptable to temperature extremes. They allow easy starting at low temperatures, yet they give good protection at high speeds and engine temperatures. This is a decided advantage in changeable climates or in long distance touring.
The American Petroleum Institute (API) designation indicates the classification of engine oil used under certain given operating conditions. Only oils designated for use "Service SG'' or better should be used. Oils of the SG type perform a variety of functions inside the engine in addition to their basic functions inside the engine in addition to their basic function as a lubricant. Through a balanced system of metallic detergents and polymeric dispersions, the oil prevents the formation of high and low temperature deposits and also keeps sludge and particles of dirt in suspension. Acids, particularly sulfuric acid, as well as other by-products of combustion, are neutralized. Both the SAE grade number and the API designation can be found on the label of the oil bottle.
For recommended oil viscosities, refer to the chart.
Non-detergent or straight mineral oils should not be used in your car.
There are many excellent synthetic and fuel-efficient oils currently available that can provide better gas mileage, longer service life, and in some cases better engine protection. These benefits do not come without a few hitches, however, the main one being the price of synthetic oils, which can be three or four times the price per quart of conventional oil.
Synthetic oil is not for every car and ever type of driving, so you should consider your engine's condition and your type of driving. Also, check your car's warranty conditions regarding the use of synthetic oils.
Both brand new engines and older, high mileage engines may be the wrong candidates for synthetic oil. The synthetic oils are so slippery that they may prevent proper break-in of new engines; most manufacturer's recommend that you wait until the engine is properly broken in - 5,000 miles (8,046 km) - before using synthetic oil. Older engines with wear have a different problem with synthetics. Slippery synthetic oils get past worn parts easily. If your car is leaking oil past old seals you'll have a much greater leak problem with synthetics.
Consider your type of driving. If most of your accumulated mileage is high speed, highway type driving, the more expensive synthetic oils may be of benefit. Extended highway driving gives the engine chance to warm up, accumulating less acids in the oil and putting less stress on the engine over the long run. Under these conditions, the oil change interval can be extended (as long as your oil filter can last the extended life of the oil) up to the advertised mileage claims of the synthetics. Cars with synthetic oils may show increased fuel economy in highway driving, due to less internal friction. However, many automotive experts agree that 50,000 miles (80,465 km) is far too long to keep any oil in your engine.
Cars used under harder circumstances, such as stop and go, city type driving, short trips, or extended idling, should be serviced more frequently. For the engines in these cars, the much greater cost of synthetic oils may not be worth the investment. Internal wear increases much quicker on these cars, causing greater oil consumption and leakage.
All Tercels covered in this information are designed to run on unleaded fuel. The use of leaded fuel in a car requiring unleaded fuel will plug the catalytic converter (NEVER USE LEADED FUEL IN AN UNLEADED VEHICLE), rendering it inoperative and will increase exhaust back-pressure to the point where engine output will be severely reduced. In all cases, the minimum octane rating of the fuel used must be at least Research Octane No. 91 (pump octane rating 87) or higher.
The use of a fuel too low in octane (a measurement of anti-knock quality) will result in spark knock. Since many factors affect operating efficiency, such as altitude, terrain, air temperature and humidity, knocking may result even though the recommended fuel is being used. If persistent knocking occurs, it may be necessary to switch to a higher grade of fuel. Continuous or heavy knocking may result in engine damage.
Your engine's fuel requirement can change with time, mainly due to carbon buildup, which changes the compression ratio. If your engine pings, knocks or runs on, switch to a higher grade of fuel. Sometimes just changing brands will cure the problem. If it becomes necessary to retard the timing from specifications, don't change it more than a few degrees. Retarded timing will reduce power output and fuel mileage, it will also increase the engine temperature.