I used LM Ceratec after flushing in my HJ60, 2H, 3980cc, 6 cyl stock diesel engine, 415000 kms driven, awesome performance, it depends on the condition of the engine as well, as my jeep had 6 to 7 previous owners and don't know the exact maintainence history so I did it as preventive maintainence and result is smooth engine with good mileage, getting 8-8.5km/l with AC in city and 10km/l with AC on motorway, I just did 2700 km trip to skardu and hunza in only 6 days and not a single problem alhamdolilah, our journey continued upto 40 hrs with AC continuous drive with only one hr breaks each for breakfast, lunch or dinner. Also I am using Toyota Anti freeze coolant without water and my jeep started in -10C in kalam in February this year without a problem. Its hard to spend on preventive maintenance (in my case it has large oil capacities e.g engine oil 9.5l, coolant 15l etc) but it pays.