See Figure 1
The Society of Automotive Engineers (SAE) 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 10W-40, 20W-50, etc. For example, 10W-40 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 20W-50 oil would therefore be slightly heavier and not as ideal in cold weather as the 10W-40, 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.
Honda does not recommend the use of any oil additive or supplement in the engine. A normal engine does not need them. If the engine is worn or damaged, it's usually too late for any benefit.
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 SH" should be used. Oils of the SG/SH type perform a variety of functions inside the engine in addition to the basic function as a lubricant. An SG/SH rated oil may be substituted for SF or SE oils in older vehicles. A new vehicle requiring SG/SH oil may be damaged by using oil with a lesser rating. API labels may also carry other letter ratings such as CD or CC; these oils are acceptable for use as long as the designation SG/SH is also present.
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 label of the oil bottle. For recommended oil viscosities, refer to the accompanying chart.
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 drawback is the price of synthetic oils, which is three or four times the price per quart of conventional oil.
Synthetic oil is not for every car and every type of driving, so you should consider your engine's condition and your driving situation. Also, check your vehicle's warranty conditions regarding the use of synthetic oils.
Both brand new engines and older, high mileage engines are usually the wrong candidates for synthetic oil. The synthetic oils are so slippery that they may prevent the proper break-in of new engines; most oil manufacturers recommend that you wait until the engine is properly broken in (at least 3000 miles) before using synthetic oil. Older engines with wear have a different problem with synthetics. The slippery synthetic oils get past these worn parts easily. If your engine is leaking conventional oil, it will use synthetics much faster. Also, 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 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. Cars 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 engine and must be drained regularly to prevent damage
Vehicles 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, causing greater oil consumption and leakage.
It is important to use fuel of the proper octane rating in your Honda. 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.
Fuel of the proper octane rating will slow the combustion process sufficiently to allow the spark plug enough time to ignite the mixture completely and smoothly. The use of super-premium fuel is no substitution for a properly tuned and maintained engine. Chances are that if your engine exhibits any signs of spark ping, detonation or pre-ignition when using regular fuel, the ignition timing should be checked against specifications or the cylinder head should be removed for decarbonizing.
All Accords and Preludes covered by this information are equipped with catalytic converters and must use UNLEADED GASOLINE only. Use of leaded fuel shortens the life of spark plugs, exhaust systems and EGR valves. It can also damage the catalytic converter. These engines are designed to operate quite efficiently using unleaded gasoline with a minimum rating of 91 octane. Use of unleaded gas with octane ratings lower than 91 can cause persistent spark knock which could lead to engine damage.
Some light spark knock may be noticed when accelerating or driving up hills, particularly with a carbureted engine. The slight knocking may be considered normal (with 91 octane) because the maximum fuel economy is obtained under conditions of minimal knock. Gasoline with an octane rating higher than 91 may be used, but it is not necessary for proper operation of a properly tuned engine.
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, first switch to a different brand of fuel, not a higher grade. Each refiner incorporates certain chemicals into the fuel; some engines show a definite preference for one brand or another.