That buttery smooth engine after an oil change never lasts

[l008com]

My truck only suggests I change the oil every 6000 miles or so.
The oil I use is high milage full synthetic that says it's good for 10000 miles, maybe more.
I don't drive much but I change the oil twice a year anyway. Yesterday I did my fall change and the oil still had 61% life left according to the truck. But it was 6 months old.

When I change the oil, the engine runs buttery smooth, but it never lasts. Why is that? What exactly is going on?

Is it all placebo effect? It really feels like it's not. Right after an oil change, the engine feels like it's literally a brand new engine just off the lot. but after a few weeks or so, it goes back to normal. Which is still very good for an engine with 150,000 miles. But not as good as it is JUST after the change.

Does high end oil change quickly once it's in use? Still working for many more months but never working as good as it did the first few weeks? Or is it all in my head and the engine always runs the same?

 

[Sparky]

Which oil?

I've never noticed that. I notice more effects by weather (temperature/humidity) than an oil change. Get some good 65-75 degree weather with clear, low humidity air and every car I've had just runs awesome due to being able to breath so clearly.

Call me crazy but I always changed the oil when the idiot light would tell me to. When I had the '02 TB that I had a good amount of highway cruising thrown in with the city stop-n-go, that would be 10-12k miles on average, a few times got to 14k. I know, some people would scream at me "YOU'RE GUNNA KILL IT" but heck that thing got to 215k before I got rid of it due to frame rot and it still ran great, and didn't really use or leak much oil (I can't remember now if I had to add a quart to it halfway through or not). I ran Mobil 1 in it.

The 5.3 in the '07 Silverado would get a change every 6-7k (again when the OLM would get to 10% I'd start looking for time, usually would try to change it before below 5%). It had a lower capacity so not surprised it would go less time. I had 237k on it, again ran like a top. I did have to add a quart halfway through starting around 180k-190k I think. Prior to disabling AFM it suddenly drank 2 quarts in under 2k miles, a tune-out of that crap was quick and that was the last I had any issues. Again, used Mobil 1 most of the time, though it did get the Valvoline full synthetic a handful of times when it was on sale.

Not GM, but I change the oil on the '13 Civic when it complains at me. Never had to add anything but it has under 100k miles still. And we just got the '15 Odyssey 3 weeks ago so I have no idea of its mannerisms on oil yet. It has VCM (Honda's version of AFM), and just like AFM it can cause problems like carbon buildup on the rings and oil consumption, plus it is annoying, so it is getting disabled as soon as the part I need shows up.

 

[l008com]

Usually mobile 1 high milage 5w-30 full synthetic. For the first few years, I was using mobile 1 0w-30. But 4 or 5 years ago I decided the high milage additives were probably a bigger benefit than the 0w cold starts. I live in Boston MA, not Boston Saskatchewan.

But actually yesterday it was a 5 qt of mobile 1 high milages and 1 qt of napa brand high milage which I think is just penzoil. All full synthetic.

 

[Mooseman]

Only time I noticed a change over time was with the Saab when I did the DOD delete and used the wrong oil pump. As the oil got older, pressure would not be as high and would throw a code for oil pressure sensor performance and I would notice my oil pressure wasn't as high as when the oil was new. And this usually happened at about 50% OLM. Once I swapped to the proper oil pump, all was good however I always noticed a small drop in pressure over the lifetime of the oil but still at a healthy level. That is normal for any oil or engine.

I have to say that I have never really noticed a change in performance or noise before and after a regular oil change.

 

[l008com]

Hrmmmm. Is there some way to quantify the "smoothness" of the engine before and after an oil change? I can't think of any but I'd be curious to give it a try.

ALSO I did put 6oz of seafoam in the oil a week or so ago, and 10oz of it in my gas tank. So maybe the oil was getting dirtier than normal and it was getting a little rougher, making the contract seem higher. Though it didn't feel like it was getting rougher during that week so who knows.

 

[Ilikemy3s]

I have just over 252K miles on my 05 SWB TB I6 (bought it at 85k) I used to change the oil when the OLM light came on, which since I do mostly highway driving, was averaging about 11-12 k between changes. I went with the OLM light based on the idea that if GM would risk a 5 year engine warranty on a computer computation, combined with the longevity of these motors, then it was good enough for me. However, as the miles racked up, i find myself changing the oil when it gets to about 50%.

I too agree that the engine sounds better and runs better after some fresh oil and filter .. so I008COM .. your'er not crazy ..

 

[Reprise]

I think I've noticed this, as well. Not after *every* oil change... but I've noticed engines running smoother immediately after an oil change, compared to just before.

I'll throw something new to chew on into the mix -- viscosity shear.
In short, depending on the oil, it will undergo shearing, such that a -30 weight oil (example) will take on the characteristics of a -20 weight. It seems to be oil temperature dependent (hotter = increased shear)

Some oil formulations are more shear-resistant than others. M1 (since you use that) seems to have decent resistance, just by taking a quick look at a recent post on BITOG. But BITOG, not surprisingly, also has more detailed info on shear, if you have some free time and want to find info on it.

 

[l008com]

Ok I can confirm this is definitely NOT in my head.

My engine has always had a minor tick. And it has a lot of general valve noise.
Both of which are completely gone. The engine feels amazing. And it usually does after an oil change. I don't know how long it lasts, days, maybe weeks, maybe a month? It sure is nice while it's like this though. This must have been what it was like when the original owner bought this truck brand new way back when.

 

[Mooseman]

Ah, lifter noise. LS engines are notorious for that. Probably just that little extra pressure from the new oil helps calm them down until the oil thins out a bit again. And the DOD lifters are a known failure part so no surprise there.

 

[l008com]

So a few weeks later and that super smooth new engine feel has now totally faded and the engine runs like 'normal' again until spring.