The SAE (Society of Automotive Engineers) 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, and 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.
Choose the viscosity range carefully, based upon the lowest expected temperature for the time of year. If the lowest expected temperature is 0°F (-18°C), you should use 10W-30. If it is 50°F (10°C), as in spring and fall, you can use 20W-40 and 20W-50 for their extra guarantee of sufficient viscosity at high temperatures.
The API (American Petroleum Institute) designation indicates the classification of engine oil used under certain given operating conditions. Only oils designated for use Service SE should be used. Oils of the SE type perform a variety of functions inside the engine in addition to the basic function as a lubricant. Through a balanced system of metallic detergents and polymeric dispersants, 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 byproducts of combustion, are neutralized. Both the SAE grade number and the API designation can be found on top of the oil can.
Diesel engines all require SE engine oil. In addition, the oil must qualify for ACC rating. The API has a number of different diesel engine ratings, including CB, CC and CD. Any of these other oils are fine as long as the designation CC appears on the can along with them. Do not use oil labeled only SE or only CC. Both designations must always appear together.
As of late 1980, the API has come out with a new designation of motor oil, SF. Oils designated for use Service SF are equally acceptable in your Datsun/Nissan. Non-detergent or straight mineral oils should not be used in your car.
There are excellent synthetic and fuel efficient oils available that, under the right circumstances, can help provide better fuel mileage and better engine protection. However, these advantages come at a price, which can be three or four times the price per quart of conventional motor oils.
Before pouring any synthetic oils into your car's engine, you should consider the condition of the engine and the type of driving you do. Also, check the car's warranty conditions regarding the use of synthetics.
Generally, it is best to avoid the use of synthetic oil in both brand new and older, high mileage engines. New engines require a proper break-in, and the synthetics are so slippery that they can prevent this. Most manufacturers recommend that you wait at least 5,000 miles before switching to a synthetic oil. Conversely, older engines are looser and tend to use more oil. Synthetics will slip past worn parts more readily than regular oil, and will be used up faster. If your car already leaks and/or uses oil (due to worn parts and bad seals or gaskets), it will leak and use more with a slippery synthetic oil inside.
Consider your type of driving. If most of your accumulated mileage is on the highway at higher, steadier speeds, a synthetic oil will reduce friction and probably help deliver better fuel mileage. Under such ideal highway conditions, the oil change interval can be extended, as long as the oil filter will operate effectively for the extended life of the oil. If the filter can't do its job for this extended period, dirt and sludge will build up in your engine's crankcase, sump, oil pump and lines, no matter what type of oil is used. If using synthetic oil in this manner, you should continue to change the oil filter at the recommended intervals.
Cars used under harder, stop-and-go, short hop circumstances should always be serviced more frequently, and for these cars synthetic oil may not be a wise investment. Because of the necessary shorter change interval needed for this type of driving, you cannot take advantage of the long recommended change interval of most synthetic oils.
Finally, most synthetic oils are not compatible with conventional oils and cannot be added to them. This means you should always carry a couple of quarts of synthetic oil with you while on a long trip, as not all service stations carry this oil.
All Datsun gasoline engined models covered in this guide have been designed to run on regular low-lead or unleaded fuel, 1973-79, with the exception of those models built for use in California (1975 and later) which require the use of unleaded fuel. All 1980 and later models must also use only unleaded fuel. 1975 and later California cars and all 1980 and later models utilize a catalytic converter. The use of leaded fuel will plug the catalyst, rendering it inoperative, and will increase the exhaust back pressure to the point where engine output will be severely reduced. The minimum octane requirement for all engines using unleaded fuel is 91 RON (87 CLC). All unleaded fuels sold in the U.S. are required to meet this minimum octane rating.
The use of a fuel too low in octane (a measurement of anti-knock quality) will result in spark knock. Since many factors such as altitude, terrain, air temperature and humidity affect operating efficiency, 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 will in turn increase the temperatures in the combustion chamber and change 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 about two degrees. Retarded timing will reduce power output and fuel mileage, in addition to increasing the engine temperature.
Datsun diesels require the exclusive use of diesel fuel. At NO time should gasoline be substituted or mixed with diesel fuel. Two grades of diesel fuel are manufactured, #1 and #2, although #2 is generally more available. Better fuel economy results from the use of #2 grade fuel. In some northern parts of the U.S. and in most parts of Canada, #1 grade fuel is available in the winter or, if not, a winterized blend of #2 grade is supplied. When the temperature falls below 20°F (-7°C), #1 grade or winterized #2 grade fuel are the only fuels that can be used. Temperatures below 20°F. cause unwinterized #2 to thicken (it actually gels), blocking the fuel lines and preventing the engine from running.Diesel Cautions:
It is normal that the engine noise level is louder during the warm-up period in winter. This occurs due to a normal diesel phenomenon known as ignition lag. It relates to the lower temperatures reached through compression if the combustion chambers are cold, and normally does not indicate any engine abnormality. It is also normal that whitish-blue smoke may be emitted from the exhaust shortly after starting and during warm-up. The amount of smoke depends upon the outside temperature.
If the increases in noise and smoke levels at cold temperatures seem extreme, you may wish to check on the fuel's cetane rating (you may have to ask your fuel dealer what the rating is). This is a measurement of the fuel's ability to ignite at low temperatures. The rating should be at least 42 (higher cetane numbers are more desirable).