The SAE (Society of Automotive Engineers) grade number indicates the viscosity of the engine oil; its resistance to flow at a given temperature. The lower the SAE grade number, the lighter the oil. For example, the mono-grade oils begin with SAE 5 weight, which is a thin, light oil, and continue in viscosity up to SAE 80 or 90 weight, which are heavy gear lubricants. These oils are also known as 'straight weight', meaning they are of a single viscosity, and do NOT vary with engine temperature.
Multi-viscosity oils offer the important advantage of being adaptable to temperature extremes. These oils have designations such as 10W40, 20W50, etc. The "10W40" means that in winter (the "W" in the designation) the oil acts like a thin 10 weight oil, allowing the engine to spin easily when cold and offering rapid lubrication. Once the engine has warmed up, however, the oil acts like a straight 40 weight, maintaining good lubrication and protection for the engine's internal components. A 20W50 oil would therefore be slightly heavier than and not as ideal in cold weather as the 10W40, but would offer better protection at higher rpm and temperatures because when warm it acts like a 50 weight oil. Whichever oil viscosity you choose when changing the oil, make sure you are anticipating the temperatures your engine will be operating in until the oil is changed again. Refer to the oil viscosity chart for oil recommendations according to temperature.
The API (American Petroleum Institute) designation indicates the classification of engine oil used under certain given operating conditions. Only oils designated for use "Service SJ" or greater should be used. Oils of the "SJ" 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 by-products of combustion, are neutralized. Both the SAE grade number and the API designation can be found on the oil bottle. For recommended oil viscosities, refer to the chart.
Toyota specifies API SH (SJ starting in 1999 vehicles) "Energy-Conserving II" multi-grade engine oil be used in their engines. Toyota says that SAE 5W30 is the best choice for good fuel economy and good starting in cold weather. SAE 10W30 can also be used by Toyota says that extremely low temperatures, the engine may become difficult to start, so SAE 5W-30 engine oil is recommended. If you have any questions about engine oil, please consult your Owner's Manual for the latest recommendations specific to your vehicle.
Remember that Over Head Camshaft (OHC) engines as used in these vehicles have a lot of moving parts. The camshaft lifters and camshaft bearings need lubrication as soon as the engine begins to turn. In cold weather, oil with too heavy a weight (thicker viscosity) takes a long time to get to the more remote parts of the engine. An engine can be badly damaged in the time it takes thick oil to reach all of the locations in an engine, especially those the greatest distance from the oil pump. Use the oil recommended in your Owner's Manual.SYNTHETIC OIL
There are many excellent synthetic 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 is three or four times the price per quart of conventional oil.
Synthetic oil is NOT for every truck and every type of driving, so you should consider your engine's condition and your type of driving. Also, check your truck's warranty conditions regarding the use of synthetic oils.
Both brand new engines and older, high mileage engines are often the wrong candidates for synthetic oil. Synthetic oil can be so slippery that they can prevent the proper break-in of new engines; most manufacturers recommend that you wait until the engine is properly broken in 3000 miles (4830 km) before using synthetic oil. Older engines with wear have a different problem with synthetics: they leak more oil as they age. Slippery synthetic oils get past worn parts easily. If your truck is leaking oil past old seals you'll most probably 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 a benefit. Extended highway driving gives the engine a chance to warm up, accumulating less acids in the oil and putting less stress on the engine over the long run. Trucks with synthetic oils may show increased fuel economy in highway driving, due to less internal friction.
If synthetic oil is used, it should still be replaced at regular intervals as stated in the maintenance schedule. While the oil itself will last much longer than regular oil, pollutants such as soot, water and unburned fuel still accumulate within the oil. These are the damaging elements within a motor and must be drained regularly to prevent damage.
Trucks 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 trucks, the much greater cost of synthetic or fuel-efficient oils may not be worth the investment. Internal wear increases much quicker on these trucks, causing greater oil consumption and leakage.Fuel
Your Toyota truck is designed to use unleaded gasoline only. Do NOT use leaded gasoline. Use of any leaded gasoline will cause the three-way catalytic converter to lose its effectiveness and the emission control system to function improperly. This can lead to expensive repairs.
It is important to use fuel of the proper octane rating in your truck. Octane rating is based on the quantity of anti-knock compounds added to the fuel and it determines the speed at which the gas will burn. The lower the octane rating, the faster it burns. The higher the octane, the slower the fuel will burn and a greater percentage of compounds in the fuel prevent spark ping (knock), detonation and pre-ignition (dieseling).
As the temperature of the engine increases, the air/fuel mixture exhibits a tendency to ignite before the spark plug is fired. If fuel of an octane rating too low for the engine is used, this will allow combustion to occur before the piston has completed its compression stroke, thereby creating a very high pressure very rapidly.
Toyota's octane recommendations depends on the vehicle model and even. Some vehicles can use gasoline with an Octane Rating of "87." Others require an Octane Rating of 91 or higher. Consult your Owner's manual. Use of unleaded fuel with an octane number lower than recommended will cause persistent heavy knocking. If severe, this will lead to engine damage.
Toyota says that heavy knocking, even when using the recommended fuel, or a steady knocking while holding a steady speed, should be investigated as there may be a problem with the engine. However, now and then, you may notice a light knocking for a short time while accelerating or driving up hills. This should be no cause for concern.
Toyota recommends the use of gasoline that contains detergent additives to avoid build-up of engine deposits. If you use gasohol in your Toyota, be sure that it is unleaded, has an octane rating no lower than 87 and does NOT contain more than 10 percent ethanol. Toyota does NOT recommend gasoline containing methanol. If you must use gasoline containing methanol, it must contain less than 5 percent methanol with cosolvents and corrosion inhibitors for methanol.