Regular or high octane gasoline?
A significant difference between different grades of gasoline is knock resistance. It is indicated by the octane number and is higher for high-grade gasoline.
High-octane gasoline can withstand higher compression pressures without self-ignition. Such pressure with regular gasoline would lead to detonation. During compression, the working mixture is heated, consisting of fuel vapor mixed with air.
The higher the compression ratio, the higher the probability of self-ignition of the working mixture in the combustion chamber, if the fuel does not have sufficient knock resistance. The octane number is used to characterize knock resistance. This is a comparative parameter that is determined in the test engine for a particular fuel. The term is often used «research octane number» «Research-Oktanzahl», abbreviated ROZ. Less commonly used more meaningful term «engine octane», or MOZ.
The octane rating for unleaded petrol in the Federal Republic of Germany is determined by DIN 51607, which defines the minimum fuel requirements. So, for regular gasoline, the octane number is 91, for Euro Super gasoline - 95, and Super Plus gasoline has a minimum octane number of 98.
Ringing and noise in the engine
These problems are almost never found on our engines, as they have knock control in the ignition system. However, it is necessary to describe the reason for this process.
Usually the working mixture ignites in the cylinder from the spark discharge of the spark plug in waves - as if you threw a stone into calm water: the waves diverge in a circle. Through the propagating ignition of the working mixture, the gases in the cylinder expand. If this expansion is too strong, then the unburned gas residue can be pressed against the walls of the cylinder. This increase in pressure leads to heating of the unburned residue of the working mixture, due to which it can ignite spontaneously. At the same time, it detonates towards the flame front from the spark plug. This leads to a strong increase in pressure in the cylinder. The piston receives a blow to the base and transfers it further through the connecting rod to the crankshaft bearing.
If this effect occurs at high engine speeds, then the noise generated by the combustion process is drowned out by the driving noise of the vehicle. This is very dangerous for engines with a conventional ignition system. This knocking at high speeds causes the engine to overheat significantly and can cause the piston base to melt. Better known, because they are more audible, are knock noises during acceleration. They appear if you accelerate the car on low-octane gasoline. However, this does not harm the engine.
What fuel to use for Renault 19?
Our Renault 19 models use the following fuels:
Engine | Brief designation | Compression | Gasoline regular unleaded 91 | Gasoline Euro Super unleaded 95 | Petrol Super Plus unleaded 98 | Diesel fuel 45 CZ |
1.4 liter 1.7 liter 1.7 liter 1.8 liter 16 valve Diesel Diesel with turbocharger | C3J F3N-L F3N-N F3P F7P F8Q F8Q | 9,0 9,5 9,5 9,8 10,01 21,5 20,5 | + + — — — — — | +1 +1 + + + — — | +1 +1 +2 +2 +2 — — | — — — — — + + |
1can be used;
2used at full load and high outside temperature.
During detonation, in addition to the working mixture ignited by the spark plug, its residue in the corner of the combustion chamber ignites spontaneously.
Diesel fuel
Diesel Renault 19 You must fill only with diesel fuel conforming to the State Standard DIN 51601 with cetane number (CZ) not less than 45. The cetane number characterizes the flammability of the fuel. It is a parameter that is determined in a standard test diesel.
Diesel fuel and temperature
Fuel consists of a large number of different hydrocarbons. In diesel, it is mainly about paraffin, which determines the degree of flammability. Its negative property is the tendency of paraffin to crystallize with decreasing temperature. Crystals quickly connect and form whole complexes of lattice compounds together.
Starting from a certain negative temperature, such a number of crystal lattices are formed at which the fuel no longer passes through the fuel filter.
Winter fuel
The so-called flow improvers keep the fuel flow even at low temperatures. Diesel fuel at petrol stations is divided into:
- Summer diesel fuel is the most «raw». It thickens even at -2°C.
- Transitional diesel fuel is sold in spring and autumn. It retains good fluidity at -8 to -10°C.
- Winter diesel fuel, according to the requirements of the standard, must be suitable for use at temperatures down to -12°C. As a rule, its quality is improved by the addition of flow additives, so that winter diesel fuel retains its properties down to -22°C, but further addition of additives does not bring any improvements. The recommendations of the manufacturers of mineral oils also speak of the same.
Anti-thickness agent
If you have summer diesel fuel in your tank during the cold season, you can improve its performance yourself by adding an appropriate product, such as «Autol Desolite D/DW», «LM fliessfit», «Valvoline Winterfit» or «Veedol Diesel Aktiv». Be careful, read the information on the label!
The formation of paraffin crystals cannot be prevented by flow improvers. They only prevent the formation of networks of these crystals, since the crystals themselves are small enough to pass through the fuel filter cells. Thus, the fuel enters the high pressure fuel pump.
A negative property of flow improvers is that they do not act on all types of diesel fuel in the same way. In addition, you can never be sure at what temperature the fuel poured into your tank will thicken. Anyone who wants to definitely avoid problems with thickened fuel should mentally increase by a few degrees the data promised to him on the label of the agent used.
How to make sure that fuel does not thicken in the cold
If the diesel fuel has already thickened, then pouring a flow agent into the tank will no longer help, especially if it was lying in the glove box that was frozen through. If the air temperature is well below the gelling point of the fuel, then the best way to make the fuel liquid again is to park the car in a heated garage.
In order to avoid this, before a cold night, first pour in a flow improver (If possible, it should be at room temperature), then fill the tank to the brim with fuel. The temperature of fuel in underground tanks at a gas station is always above zero, so the flow improver mixes well with the fuel. Well, if the tank is empty when refueling, then the fuel from the underground refueling tanks will warm up the remaining fuel in the tank, dissolving the paraffin crystals present there. During the trip, the contents of the tank will be properly mixed, and then it will be possible to calmly survive the Siberian frost.