Synthetic oil
I have a 2005 Dodge 1500. 5.7L Hemi. It has 73000 miles on it. I have kept the oil changes and maint. Very current. I am thinking of changing to a synthetic oil for my next oil change. Is it wort...
Forum Discussion
GM rates 5W40 for temps below 0 degrees and up to 90 degrees. Severe duty has nothing to do with the grade oil, only the ambient air temperatures under which the engine will be operated.
It seems contradictory to talk about oil temps of 245 degrees and then wanting to use a 5W40 motor oil. If your oil temp is truly above specs then I would fix the problem with a supplemental oil cooler or a larger sump or some other measure.
Oil temperature is not the problem but the protection that the oil actually provides for moving parts when under pressure, as with the main bearings. This is where multi-grade oils are less effective and the lower the weight the greater the problem. By the way the fleet truckers are moving to 10W30 for their engines and not a 5W30 oil. Cummins uses and recommends using Valvoline Premium Blue dino oil in its diesel engines and this oil has an exceptional additive mixture.
ALL SAE API rated oils have passed tests in terms of the pressure that the oil can withstand at normal operating temperatures without metal to metal contact.
This testing has also shown that polymer shearing does occur when a multi-grade oil passes through tiny apertures at high pressure and when this happens the lubricity of the oil is greatly degraded - as with oil entering main bearing journals.
What is also vastly different with diesel engines besides the introduction of soot and unburned diesel fuel into the crankcase is the high percentage of each gallon of oil that consists of additives. 25% of a gallon of oil is additives and these are not going to be as effective at 25,000 miles as they were at 5,000 miles.
I can change out the dino oil every 7500 miles and get all the soot and sludge out of the crankcase and I can put in new oil with a new batch of additives, or for the same cost I can use synthetic oil and change it out every 20,000 miles. To me the advantages of dino oil with a diesel engine are obvious in this situation.
It seems contradictory to talk about oil temps of 245 degrees and then wanting to use a 5W40 motor oil. If your oil temp is truly above specs then I would fix the problem with a supplemental oil cooler or a larger sump or some other measure.
Oil temperature is not the problem but the protection that the oil actually provides for moving parts when under pressure, as with the main bearings. This is where multi-grade oils are less effective and the lower the weight the greater the problem. By the way the fleet truckers are moving to 10W30 for their engines and not a 5W30 oil. Cummins uses and recommends using Valvoline Premium Blue dino oil in its diesel engines and this oil has an exceptional additive mixture.
ALL SAE API rated oils have passed tests in terms of the pressure that the oil can withstand at normal operating temperatures without metal to metal contact.
This testing has also shown that polymer shearing does occur when a multi-grade oil passes through tiny apertures at high pressure and when this happens the lubricity of the oil is greatly degraded - as with oil entering main bearing journals.
What is also vastly different with diesel engines besides the introduction of soot and unburned diesel fuel into the crankcase is the high percentage of each gallon of oil that consists of additives. 25% of a gallon of oil is additives and these are not going to be as effective at 25,000 miles as they were at 5,000 miles.
I can change out the dino oil every 7500 miles and get all the soot and sludge out of the crankcase and I can put in new oil with a new batch of additives, or for the same cost I can use synthetic oil and change it out every 20,000 miles. To me the advantages of dino oil with a diesel engine are obvious in this situation.
