Car Problem

[noviceman1]

Does anyone know whether it is safe to mix different types of antifreeze when topping up coolant in a diesel motor.

[deggers316]

makes no difference if its diesel or petrol
http://eco-freez.com/index.php?option=com_content&view=article&;id=118&Itemid=134

[Clanad]

Maybe... maybe not. A problem can occur with the diesel engine (mostly related to bigger diesel engines), since all diesel engines operate at much higher cylinder pressures that gas/petrol powered ones. The high pressure (as you are probably aware) is required to ignite the fuel/air mixture since there's no spark plug.
The problem is termed Cylinder Liner Caviatation explined here:

"...One of the most common and costly results of improper cooling system maintenance is the perforation of wet-sleeve cylinder liners. The perforation is caused by repetitive pitting of the liner resulting from liner vibration. As the fuel inside ignites, the liner vibrates within the block. The outside wall of the liner actually moves away from the coolant causing a near vacuum for an instant. This low-pressure causes the surrounding coolant to boil, forming tiny bubbles. The liner then returns to its position with extremely high velocity, pressing against the bubbles with a violent force. The bubbles implode (collapse) against the liner wall surface at pressures up to 60,000 PSI. The collapse of these bubbles blasts small holes in the steel liner. This pitting process will repeat, digging tiny tunnels through the liner. This will eventually perforate the wall allowing coolant to enter the combustion side of the cylinder.

Correctly formulated coolant contains either nitrite or a combination of nitrite and molybdate. They will form a thin protective oxide film on the coolant side of the liner wall. This oxide film, which is formed by reaction of the nitrite with the liner wall, acts as a protective barrier to prevent corrosion and cavitation from occurring. In a properly protected system, the imploding bubbles attack the protective film. The film quickly heals over the liner by drawing nitrite from the coolant. In an improperly protected system, the bare metal surface area is immediately exposed to cavitation forming a corroded pit in the metal."

Simply put, one can use the standard ethylene/glycol coolant used in petrol engines (gas, here in the U.S.) but an additive is required to assure the above referenced problem is dealt with... check your engine manufacturer's recommendation.
The above article offers these products as additives or alternatives for proper die engine protection: Old World Industries Fleet Charge, Prestone Heavy duty AF977, Pencool 3000, Detroit Diesel PowerCool, GM Good Wrench SCA, Caterpillar diesel coolant additive, and most recently Shell has come out with a premixed 50/50 Rotella ELC (extended life coolant) which is supposed to last for 300,000 miles. (I emphasize I'm in the U.S. so there may be a name difference in th eproducts).

[chas2008]

really need to know the vehicle is as some manufacturers do have specific coolant, if its nothing special the rule of of thumb is as long as its the same colour you shouldnt go too far wrong

[noviceman1]

Thanks....very comprehensive from the States.