Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

Fuel Recommendations

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GASOLINE ENGINES



All gasoline engine Volvos produced before the 1975 model year are designed to run on leaded (regular) gasoline. Many 1970-72 models with high compression ratios (9.3:1 to 10.5:1) require high octane fuel (97-100 RON). In recent years, it has become almost impossible to find gasoline with an octane rating this high, although some oil companies were making available a "Premium" fuel which approaches these levels. In these days of low compression, fuel efficient motors, pre-1975 cars may require a special lead-bearing additive which may be mixed with pump grade unleaded fuel.

1975 and later cars equipped with catalytic converters must use lead-free fuel or the catalyst will be rendered ineffective. These models carry an "Unleaded Gasoline Only" sticker in conspicuous view near the fuel filler cap. Other 1975 and later Volvos are designed to run on regular or low-lead fuel.

On most models, the octane rating needed to prevent engine knock is printed on a sticker inside the fuel filler cap lid. If no sticker is evident, consult your owner's manual. The most common octane requirement for Volvos is 91 RON, and this fuel is readily available.

Gasoline Octane Rating

Octane rating is based on the quantity of anti-knock compounds added to the gasoline and determines the speed at which the gas will burn; the lower the octane, the faster it burns. The higher the numerical octane rating, the slower the fuel will burn and the greater the percentage of compounds in the fuel to prevent spark ping (knock), detonation, and pre-ignition. As the temperature of the engine increases, the air-fuel mixture shows a tendency to ignite before the spark plug is fired and the exhaust valve is opened. This is especially critical in high compression engines (any engine with a compression ratio greater than 9.0:1), where the use of low-octane fuel will cause combustion to occur before the piston has completed its compression stroke, thereby forcing the piston down while it is still traveling upward. Fuel of the proper octane rating for your engine's compression ratio will slow the combustion process sufficiently to allow the spark plug time to ignite the mixture completely and allow time for the exhaust valve to open. If allowed to occur, spark ping, detonation, or pre-ignition may result in damage to the top of the pistons and burned exhaust valves.

DIESEL ENGINES



The early Volvo diesel engine is designed to run on No. 2 Diesel Fuel. From 1984 through 1986, Volvo diesels can run on either No. 1 or No. 2 fuel. Since diesel fuel is generally available along major truck routes, supply is not a problem, though it is wise to check in advance.

Several diesel station guides are available from fuel companies and are normally sold at diesel fuel stations. Some U.S. states and Canadian provinces require purchasers of diesel fuel to obtain a special permits. Check with your Volvo dealer or fuel supplier for regulations in your area. Volvo recommends that you buy diesel fuel from major suppliers to ensure a uniform high quality of fuel. For proper operation, diesel fuel systems must not contaminated by using inferior quality fuel. Special winter blends are available and should be used when temperatures fall below 14°F (-10°C). These fuels reduce the potential of wax deposit formation in the system and the resulting fuel flow restrictions. Most diesel fuel stations automatically switch to these blends when the cold weather approaches, but just to be sure, ask the attendant before filling up.


WARNING
There is a dramatic difference between the refinement levels of diesel fuel and home heating oil. As some diesel owners have found out the hard way, substituting home heating oil for diesel fuel will clog the fuel system with impurities and ash, resulting in the need for a major fuel system cleaning and overhaul.

 
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