Fuel System - Operating Fluids BMW X3 E83

1.0 Fuels for Gasoline Engines

Use only unleaded gasoline in vehicles equipped with a catalytic converter.

Gasolines are expected to fulfill many requirements to guarantee the desired operating conditions during all environmental and driving conditions.

For application in BMW cars it is permitted to add up to and including 10% ethanol or other oxygenates with up to 2.8% oxygen by weight (i.e. 15% MTBE or 3% Methanol plus an equivalent amount of co-solvent). However, driveability problems may result from the use of such fuels, especially under certain environmental conditions such as high ambient temperatures and high altitudes.

Anti-Knock Properties

The anti-knock value is the quality rating for gasoline and is a requirement for controlled combustion. Anti-knock value is expressed with an octane number. A higher number indicates better anti-knock properties of a gasoline. Internationally approved methods are used to determine the Research Octane Number (RON) and the Motor Octane Number (MON). In the United States the Anti-Knock Index (AKI) is displayed at the gas pumps.

AKI = RON + MON\2

Boiling Range and Vapor Pressure

Gasolines must be highly volatile. The boiling range and vapor pressure values are used for evaluation. Gasolines do not have a boiling " point", but rather a boiling " line", since they are produced from a mixture of various hydrocarbon components.

The boiling line (boiling range) and therefore vapor pressure have influence on, for example

1. Vapor Lock
2. Starting Behavior
3. Evaporation Loss
4. Transition And Driving Behavior
5. Engine Oil Dilution
6. Perfect Combustion

The boiling range is different for summer and winter gasolines. The vapor pressure test is another means of determining the behavior of a gasoline.

Specific Gravity

The specific gravity is determined by gasoline components. The volume changes with the temperature. Due to the different compositions there are different values for premium grade and regular grade gasolines.

Calorific Value

The calorific value expresses the power content of a gasoline. The calorific value of a combustible fuel/air mixture is of prime importance for the power output of engines.

Purity, Combustion Deposits

Gasolines must be free of contamination. Pumps, jets, injectors, valves and lines must not be clogged or plugged up.

Residue and deposits in the intake system and combustion chamber will impair engine operation. The solid residue from evaporation of gasoline provides information on the degree of contamination.

Sulfur Content

The sulfur content of all gasolines should be as low as possible. In this manner there will be less sulfuric acids or sulfur acids in the combustion residue, which would lead to corrosion and sulfuric emissions on an engine running without reaching operating temperature.

1.1 Minimum Octane and AKI Ratings for Gasoline Engines

MINIMUM OCTANE AND AKI RATINGS FOR GASOLINE ENGINES

1.2 Summary of Fuel Grade Requirements

SUMMARY OF FUEL GRADE REQUIREMENTS

SUMMARY OF FUEL GRADE REQUIREMENTS

2.0 Fuels for Diesel Engines

Diesel fuel is obtained from distilled crude oil. The distilling process is highly complicated, involving precise control of temperatures and pressures. The diesel fuel quality will vary depending on the refining process and the crude oil source.

BMW of North America recommends using automotive diesel Fuel No. 2 with a minimum cetone rating of 45 for use in the BMW 524td. Never use other fuels such as marine fuel or heating oil, since these fuels do not have the appropriate additives or cetane values.

The cetane number is a measure of the fuel's ignition quality, which influences both the ease of starting and combustion stability.

A high cetane number diesel fuel promotes spontaneous burning of the fuel, which is beneficial in a diesel.

Factors which are important qualities of diesel fuel are the Cloud Point (the temperature at which wax forms in diesel fuel) and the Pour Point (the temperature at which fuel stops flowing). These qualities become very important during low temperature operation. As the temperature drops, wax can sometimes form in the fuel tank, fuel lines and/or fuel filter. If this occurs, the fuel supply lines will become clogged and resulting hard starting and rough running problems.

Temperatures below 20°F (-7°C) are critical to the formation of wax crystals. The following guidelines should solve any cold weather problems which may arise

Note. BMW 524td's are equipped with an integral fuel heater, pre-delivery fuel pump, large capacity fuel filter/water separator, and block heater for cold weather operation which should be sufficient for all but the most extreme cold weather.

If outside temperature is above 20°F (-7°C)

1. *Use Diesel Fuel No. 2

If outside temperature is below 20°F (-7°C)

1. Diesel Fuel No. 1, if available, should be used.
2. Customers should ask if diesel fuel is winterized.
3. Diesel Fuel Flow Improver can be added to diesel fuel No. 2 to lower the Cloud Point of the fuel.

Note. (1) 100 ml can of additive will treat 1 tank full of diesel fuel; additional quantities will not lower the Cloud Point any further.

Diesel Fuel Flow Improver - Wurth Part No. 893532 (former BMW Part No. 81 22 9 407 289)

Scheme 155

1. Diesel Fuel No. 2 can be mixed with kerosene in the proportions shown on the graph. Engine performance will be reduced with more than a 50% mixture of kerosene.

Note. * Significant improvement in operation can be achieved by using a combination of both kerosene and the diesel fuel flow improver since the kerosene lowers the point at which the wax formation occurs and the additive modifies the structure of the wax crystals for better flow.

3.0 Other Fluids

The throttle housing studs are to be coated with Loctite 290 on 1991-92 E30 with M42 engine.

See S.I. Bulletin B 13 06 91 (3440).

The throttle body assembly of M42 engines in E36 vehicles produced from 1/94-6/94 are to be lubricated with Optimoly

Paste TA Spray, BMW Part No. 83 23 1 468 932.

See S.I. Bulletin B 13 03 94 (4042).