Change Oil Fall or Spring

[Colin Stone]

When we used red diesel full of sulphur, I changed every autumn. Now use Ultra Low Sulphur Diesel and get oil tested every autumn, sump holds 20+ litres. Plus engine has an enormous oil filter.
Last oil change in Apr 2016. The oil I use, Millers Multi Fleet 15-40 CI, has a Total Base Number of 10.4 when new. This is a measurement of alkalinity and reduces as the Base buffers the acid products of combustion. The recommended limit is 75% of original. So, min 7.8. End of last year TBN was still 9.8 after 650 hours, still long way to go. Other important indicators were soot 0.5%, fuel dilution 0.5%, water 174ppm. No oxidation, or nitration. So, I change when the chemists tell me to!! Just taken this year's sample, so will know in a couple of weeks or so.

[rslifkin]

Originally Posted by Colin Stone

When we used red diesel full of sulphur, I changed every autumn. Now use Ultra Low Sulphur Diesel and get oil tested every autumn, sump holds 20+ litres. Plus engine has an enormous oil filter.
Last oil change in Apr 2016. The oil I use, Millers Multi Fleet 15-40 CI, has a Total Base Number of 10.4 when new. This is a measurement of alkalinity and reduces as the Base buffers the acid products of combustion. The recommended limit is 75% of original. So, min 7.8. End of last year TBN was still 9.8 after 650 hours, still long way to go. Other important indicators were soot 0.5%, fuel dilution 0.5%, water 174ppm. No oxidation, or nitration. So, I change when the chemists tell me to!! Just taken this year's sample, so will know in a couple of weeks or so.

Analysis is definitely a useful metric. And the more oil the engines hold, the more analysis pays off. On the other hand, for engines that don't hold a ton of oil, it may not make sense as more than an occasional check to confirm that you're not going too long between changes or changing way too early. My engines, for example, only take a little over 5 quarts of oil at change time, so the cost of oil and filter is hardly any more than the cost of an analysis with TBN.

[bcboomer]

Originally Posted by tkeithlu

Shouldn't make a difference. The old oil has got a few minor acids in it, but nothing that is going to hurt your engine. What does make a difference is warming up the oil before you change it, so it all drains out. Which time makes it more convenient for you to do that?

I'm not sure I understand the logic of this. When the engine was last run it was warm and the oil drained into the pan as much as it will ever drain. Modern multi grade oils drain from the pan even when at room temperature.

Running the freshly changed engine to circulate clean oil and check for leaks is important.

[Icarus]

Dozens of post about oil change timing.
Obviously it doesn't make any difference when you change the oil.

[David Mathis]

After rebuilding a few engines and seeing many more disassembled, I'm yet to see an engine with rust inside other than those that had water inside the crankcase, usually from abuse or neglect. Change fall or spring, not much difference with modern oils.

[David B]

Originally Posted by Colin Stone

When we used red diesel full of sulphur, I changed every autumn. Now use Ultra Low Sulphur Diesel and get oil tested every autumn, sump holds 20+ litres. Plus engine has an enormous oil filter.
Last oil change in Apr 2016. The oil I use, Millers Multi Fleet 15-40 CI, has a Total Base Number of 10.4 when new. This is a measurement of alkalinity and reduces as the Base buffers the acid products of combustion. The recommended limit is 75% of original. So, min 7.8. End of last year TBN was still 9.8 after 650 hours, still long way to go. Other important indicators were soot 0.5%, fuel dilution 0.5%, water 174ppm. No oxidation, or nitration. So, I change when the chemists tell me to!! Just taken this year's sample, so will know in a couple of weeks or so.

Interesting to know the cost of the analysis vs. the cost of the oil.
For me, I just don't like running with black oil, so we change every year (50 to 150 hours), but then we only take 7 litres or so.

[nmccubbin]

I think it is best to let the engine sit in clean oil, free of combustion by-products, for the winter.
Prior to first start in Spring we hold down the engine stop lever while spinning the engine for about 30 seconds, to get the bearings full of oil