I would like to make some comments about oil mixing, that is mixing different brands of oil, the thought that it's okay.
We have a diesel generator at a remote site and because of some company politics I won't mention the brand name or the oils involved but talk about the problem in general. This gen/set gets run infrequently but when it runs it's at full load and 3,600 rpm. It gets run for sometimes 3-10 minutes and sometimes for 8-10 hours and anything in between but seldom over 10 hours. Most runs are under 10 minutes and the time between runs is almost always an hour or so and it never sits for more than 2 hours, ever.
The mechanics, trying to be kind to this important engine were changing the oil frequently, sometimes changing it when they were present at the remote site event though the Hobbs meter might indicate well under 100 hours, sometimes less than 50. Because of this ad hoc schedule they would change the oil when they were at the sight and use whatever oil they had on the truck as long as it was one of their diesel rated oils and was 15w-40. Also, because of an oil cooler and associated lines about 10% of the approximately 3 gallons of oil remained behind even if the thermostatic valve was open.
Well, there was a problem. At about a quarter of the expected engine life based on previous experience with this engine/generator, the engine shut down on a short run and would not restart, no oil pressure. On tear down the engine was a mess. Scoring on the crankshaft and camshaft, damaged bearings, oil pump pickup screen completely sludged up and oil seals completely shot. The lab told us it was a clash of additives specifically the rust inhibitors and non-zinc vs zinc anti-wear additives. The oil and water failed to keep separated and the resulting mixture was not a good lubricant. Evidently because of short runs and a very large oil sump the crankcase always had some moisture present that was never burnt off until a long run. Because the oil and water never mixed this was not a problem in the past twenty years with this kind of setup at several sites. The clash of rust inhibitors and anti-wear additives in the presence of moisture killed the engine long before is time. It was determined that rebuilding the engine was not feasible and a new long block was ordered. You can bet that there are some new maintenance requirements in place and mixing brands of oils is now prohibited.
I think that when oil experts answered the question about mixing engine lubrication oils their answer was that the oils would mix with each other, that they were miscible but there was no guarantee that the resulting homogeneous mixture would meet any previously accepted standards for either oil.
We have a diesel generator at a remote site and because of some company politics I won't mention the brand name or the oils involved but talk about the problem in general. This gen/set gets run infrequently but when it runs it's at full load and 3,600 rpm. It gets run for sometimes 3-10 minutes and sometimes for 8-10 hours and anything in between but seldom over 10 hours. Most runs are under 10 minutes and the time between runs is almost always an hour or so and it never sits for more than 2 hours, ever.
The mechanics, trying to be kind to this important engine were changing the oil frequently, sometimes changing it when they were present at the remote site event though the Hobbs meter might indicate well under 100 hours, sometimes less than 50. Because of this ad hoc schedule they would change the oil when they were at the sight and use whatever oil they had on the truck as long as it was one of their diesel rated oils and was 15w-40. Also, because of an oil cooler and associated lines about 10% of the approximately 3 gallons of oil remained behind even if the thermostatic valve was open.
Well, there was a problem. At about a quarter of the expected engine life based on previous experience with this engine/generator, the engine shut down on a short run and would not restart, no oil pressure. On tear down the engine was a mess. Scoring on the crankshaft and camshaft, damaged bearings, oil pump pickup screen completely sludged up and oil seals completely shot. The lab told us it was a clash of additives specifically the rust inhibitors and non-zinc vs zinc anti-wear additives. The oil and water failed to keep separated and the resulting mixture was not a good lubricant. Evidently because of short runs and a very large oil sump the crankcase always had some moisture present that was never burnt off until a long run. Because the oil and water never mixed this was not a problem in the past twenty years with this kind of setup at several sites. The clash of rust inhibitors and anti-wear additives in the presence of moisture killed the engine long before is time. It was determined that rebuilding the engine was not feasible and a new long block was ordered. You can bet that there are some new maintenance requirements in place and mixing brands of oils is now prohibited.
I think that when oil experts answered the question about mixing engine lubrication oils their answer was that the oils would mix with each other, that they were miscible but there was no guarantee that the resulting homogeneous mixture would meet any previously accepted standards for either oil.