If an engine is quieter after an oil change, why?

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RedCorvette

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So I had the oil changed on two cars after about a year.

One had M1 0w40 before and after, and it was a 6k interval. The oil was quite black, but as we know that oil can last much longer than 6k. It's the MB 5.5 V8 engine. The new oil was GF5/SN, the old oil might not have been.

The second went from Valvoline Synpower to Quaker State Ultimate Durability, both 5w30. It did 3.5k. Oil was not as black. Both oils were GF4/SM.

But both cars were noticeably quieter after the oil change.

What is the reason? Is it due to shearing and the fact that the new oil is now the correct weight?
 
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It could be your imagination. We've all been there. Kind of like how a car is better performing after it's been washed.

But, there could be something to it. I've read reports before where someone felt things were quieter with QSUD.
 
Originally Posted By: RedCorvette
So I had the oil changed on two cars after about a year.

One had M1 0w40 before and after, and it was a 6k interval. The oil was quite black, but as we know that oil can last much longer than 6k. It's the MB 5.5 V8 engine. The new oil was GF5/SN, the old oil might not have been.

The second went from Valvoline Synpower to Quaker State Ultimate Durability, both 5w30. It did 3.5k. Oil was not as black. Both oils were GF4/SM.

But both cars were noticeably quieter after the oil change.

What is the reason? Is it due to shearing and the fact that the new oil is now the correct weight?


Because you haven't turned the key yet?
grin.gif


I've noticed the same thing, and I don't really know why it happens. It could be purely a placebo effect, or it could be that new oil does baffle sound better than used oil.
 
Originally Posted By: barlowc
It could be your imagination. We've all been there. Kind of like how a car is better performing after it's been washed.

But, there could be something to it. I've read reports before where someone felt things were quieter with QSUD.


The washing effect could be explained by air resistance.
wink.gif
 
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http://en.wikipedia.org/wiki/Psychoacoustics

It's the same phenomenon that "audiophiles" often use to describe how certain speaker cables "sound better". It's a very real thing. It doesn't mean your crazy. It just means that you're hearing may not accurately represent the noise being produced.

If you managed to do some ABX testing of the same engine in a controlled environment with difference brands of oil (not easily accomplished, obviously), I'd have a tough time believing that one could actually tell a difference.

Keep in mind, I "hear" these differences, too! I'm not throwing stones. But I know enough not to know that my perceptions may not actually match reality.
 
Originally Posted By: greystone
don't forget... it could be the filter. It would most likely flow better when new.


Someone on these forums once said that the oil pump maintains the correct pressure so oil filter restriction does not play a part.

However, a few months ago, I had one of these cars parked outside for a few days during cold weather and was surprised how well the car felt when driving cold compared to all the other times I had driven it after starting when in the garage.

I think that due to the cold the bypass had opened so oil was flowing more freely and I could definitely feel a difference.
 
Originally Posted By: JOD
http://en.wikipedia.org/wiki/Psychoacoustics

It's the same phenomenon that "audiophiles" often use to describe how certain speaker cables "sound better". It's a very real thing. It doesn't mean your crazy. It just means that you're hearing may not accurately represent the noise being produced.

If you managed to do some ABX testing of the same engine in a controlled environment with difference brands of oil (not easily accomplished, obviously), I'd have a tough time believing that one could actually tell a difference.

Keep in mind, I "hear" these differences, too! I'm not throwing stones. But I know enough not to know that my perceptions may not actually match reality.


But oil reduces friction, and friction causes sound, and we change old oil because it is not protecting as well. So there might be some truth to the fact that new oil is cushioning better than old oil.

The M1 0w40 could have been an SM > SN effect. On the other hand it was a year OCI and it's recommended to change oil at 1 year regardless of mileage as it just wears down.

The Synpower > QSUD could be related to the oil differences.

One other thing, after sitting for a few hours after a freeway drive, I started up the 5.5 V8 and it sounded noisier at idle (which was weird because prior to that it had seemed quieter then before the oil change). I was wondering why and just realized that the accoustics might have been different as I was in an underground car park.
 
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I can always tell the difference when I put fresh oil in an engine.
It is not your imagination.
Fresh oil with fresh additives, especially friction modifiers?
I don't know, but even replacing like with like, you can tell the difference.
 
I changed my oil in my 1995 nissan about a month ago with Quaker State Defy and I can tell you that it is much quieter and smoother. My dad also noticed it without me saying anything to him. I also put some BG RF7 in it as well.
 
Originally Posted By: RedCorvette

But oil reduces friction, and friction causes sound,


true, I'm with ya..

Originally Posted By: RedCorvette
and we change old oil because it is not protecting as well. So there might be some truth to the fact that new oil is cushioning better than old oil.


you lost me right here... do you really think anyone on this forum is waiting until their oil in no longer providing adequate protection before changing it? Seriously, I can think of that one poster who did a 25K OCI on his Cavalier, but that's about it! No one on here is changing oil that isn't protecting adequately. If anything, the newer/fresher oil is protecting LESS well during the initial couple of hundred miles (this has been well-established in both lab and field tests). So, based on that logic the new oil should be noisier! But, that's not the sound one expects to hear.



Originally Posted By: RedCorvette
The M1 0w40 could have been an SM > SN effect. On the other hand it was a year OCI and it's recommended to change oil at 1 year regardless of mileage as it just wears down.

The Synpower > QSUD could be related to the oil differences.

One other thing, after sitting for a few hours after a freeway drive, I started up the 5.5 V8 and it sounded noisier at idle (which was weird because prior to that it had seemed quieter then before the oil change). I was wondering why and just realized that the accoustics might have been different as I was in an underground car park.


I'm not discounting that there could be legitimate differences in sound. However, the differences would be tiny, and discerning these differences difficult, under the best of conditions. Add in all of the other variables (such as the acoustics you just mentioned, and a bunch of other stuff), and I think making determinations about motor oil based on noise is a real tough one.
 
Originally Posted By: fdcg27
I can always tell the difference when I put fresh oil in an engine.
It is not your imagination.


It may not be your imagination, but you can still "hear" effects which are not actually present. So, it's not really that you're "imagining" the sound, but that you're processing the wave forms in a different manner. It's a real, easy-to-document phenomenon. And, since I have an oil change coming up, in the interest of science and all things BITOG, this gives me a great idea for an experiment!
 
Originally Posted By: JOD
Originally Posted By: RedCorvette
and we change old oil because it is not protecting as well. So there might be some truth to the fact that new oil is cushioning better than old oil.


you lost me right here... do you really think anyone on this forum is waiting until their oil in no longer providing adequate protection before changing it? Seriously, I can think of that one poster who did a 25K OCI on his Cavalier, but that's about it! No one on here is changing oil that isn't protecting adequately. If anything, the newer/fresher oil is protecting LESS well during the initial couple of hundred miles (this has been well-established in both lab and field tests). So, based on that logic the new oil should be noisier! But, that's not the sound one expects to hear.


So you don't believe that there is a gradual deteroriation in the oil? You said that for the first couple of hundred miles it is worse, so that implies there is a gradual improvement during that period. Deteroriation and Improvement are unlikely to be binary.

Doesn't the oil weight also change with use? M1 0w40 is supposed to go to a 0w30 quite quickly. New M1 0w40 is thicker than used.

Thicker oil would insulate sound more. I felt a similar effect when going from 5w20 to 5w30. I also noticed a smoother, more cushioned engine when going from syn blend to full syn in the same weight.
 
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Originally Posted By: JosephHarmon
You cranked up with cold oil, cold heads, and as it warmed and thinned you didn't notice the gradual audible change.


I'm actually refering to the sound when warmed up and accelerating a little harder. I only rev to 3k and above when the oil is warmed up.
 
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