When to change the engine oil

I've always been told to change the oil & filter at the end of the season when winterizing. It seems to me it would be better to change it at the beginning of the season so as to start out with "fresh" oil. I guess the question would be is it better to have new or used oil sitting in there all winter, or does it matter? What do you guys do?

Dave

You should change your oil at the end of the season. Used oil is caustic and will damage your engine internally.

Be sure to change it when the oil is hot...the hotter the better...The engine needs to run for at least 30 minutes(preferably longer) to thoroughly warm the oil....changing cold oil leaves sludge and dirt behind and is of little value in prolonging engine life.

dcbullington said:

............. I guess the question would be is it better to have new or used oil sitting in there all winter, or does it matter?
What do you guys do?

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Dave, Chris is correct.
This has to do with combustion by-products that cause acidity within the used oil.
When changing during lay up, this is mostly eliminated, if not completely eliminated.

Ditto warming the engine up prior...... makes filter removal much easier as well.
Be sure to run the engine after the change.

Second question:
If I have changed oil prior to lay up, and if I don't have too much time on the oil (maybe 10 hours or so)......, I'll sometimes leave it alone.


Dave, there will also be those who suggest changing sea water pump impellers at this time also.
I don't believe in leaving an impeller in the pump cavity for this duration..... w/ three/four impeller blades folded over against the cam.
The material takes a "set" and I like to avoid this.
I'll get much better life from my impellers when I remove them, and/or when I do not replace until re-commissioning in the spring time.

Just an FYI on that!
.

IMO, 10 minutes or 10 hours of combustion by-products are equally harmful. In fact, I would say that until the engine warms up and is at its most efficient, it's dumping all kinds of nasties into the oil. Not willing to take a gamble with prescious hardware sitting in that soup during the off season for the sake of the price of oil and a filter. The engines that seem to suffer the most due to this mindset are generators..."I hardly used mine this summer, so I don't see the need to change the oil." Now having said that, oil has a shelf life; it's pretty much 90 days after exposed to air for optimal protection. That's why they suggest oil changes by the millage or 90 days which ever comes first. Merc for example is getting pretty sticky on this for warranty issues. For the ultimate protection, you want to remove the nasty stuff at the end of the season but also ensure that there is fresh oil at the beginning of the season rather than 4-5 month old oil. I know some folks that will put the cheapest stuff available for winter haulout, run on this for a few hours in the spring, then switch to a good quality oil. It may be overkill but hey, what ever helps you sleep at night!!

Woodie, I don't normally disagree with anything from your posts! In fact, we tend to see much of this very similarly.

However, I think that in this case, I'd have to suggest that oil contamination (due to combustion by products) will be somewhat proportionate to run time.
One tell-tale sign would be oil discoloration as engine hours tick away on the fresh oil change.
I'd certainly not leave 10 hour oil in for the winter if it was beginning to show signs of discoloration beyond what I'd expect.
On that note, I'd agree with you in that 10 hours may be too long.

Just my two cents on that!

Thanks guys, at least now I understand the logic re: not starting out each season by changing the oil. Since the transmission does not get combustion contaminates, I assume that oil change is driven by hours, right?Dave

dcbullington said:

............... Since the transmission does not get combustion contaminates, I assume that oil change is driven by hours, right?

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Dave, the first part of that would be correct! No combustion bi-product contaminates!

Many drives, and perhaps some I/B transmissions use a magnetic drain plug, of which is ideal for sampling how much carbon steel material is wearing away.
(it won't catch brass or bronze, but that may be suspended in the oil)

What I do for an I/O, is I leave the upper vent fitting installed and I open the drain port, and catch the first several ounces of gear oil.
I then examine it.
For an I/B, you could simply take a sample from either the drain port or a fill port using a suction tube to reach the bottom.
If the oil is not contaminated, there is really no reason to change it.
Or conversely, if it is contaminated, it's time to change it..... and perhaps find out why it's contaminated!

Of course if there is any doubt, the best thing to do would be to change it.

.

I get what you're saying Rick but I'm used to recommending a change if the engine has been run at all; overkill? maybe. If I get to the engine then fine, I'll make the determination based on what I see and smell but it's usually a question posed by someone who's doing his own work and I can't advise not changing the oil even after only 10 minutes without seeing for myself how the engine is running even if they tell me the colour is good, that is relative. Thier view on what looks good is certain to be different from mine; fuel laden oil due to a poor running engine or a hardware malfunction may not be apparent at a glance. I just feel more comfortable doing it that way!

PS; who ever gives you true run time info anyway when it comes to service?!

Good points, Woodie!