Explain How Oil Can Make An Engine "Smoother"

[Garak]

Originally Posted By: dnewton3
I will admit that large, significant shifts in oil selection might have some effect. Going from a 0w-20 to a 15-40 at start-up might make something a bit noiseier or quieter.


I would agree. The only time I've ever had a noticeable difference was with my 1984 F-150 with the 4.9L before the rebuild. That engine was leaking, rattling, knocking, and had crankshaft play. So, with MaxLife 5w30, it ran noticeably quieter, as it did with 15w40 HDEO. It was noisier with Mobil High Mileage, as noisy as with any regular conventional oil; I didn't expect that.

However, with a well maintained engine, I don't think that one could hear the difference between, say, Quaker State 5w30 and Castrol GTX 5w30. If one went from 5w-20 to 20w-50, perhaps then....

 

[oblivion]

I'll add my .02 to this.

About 10 years ago I had a 92 Caprice with a 5.7L. (was a used cop car) The motor ran great though it had the infamous GM piston slap at startup. It had around 180K on it at the time. My oil pan rusted out and I had a local shop replace it. Ignoring my desires, they refilled the oil with Pennzoil conventional 10w30 oil. I swear it sounded and felt like the crankcase was full of fine gravel, though the oil pressure was the same and performance seemed unchanged. I ended up doing an OC after only about 200 miles and refilled it with Mobil 1 of same grade. Instant quiet again. (The piston slap was unaffected by either oil)

 

[fdcg27]

I have never been one to go for loud exhausts.
Inside or out, thicker oils do seem to make for quieter operation in those cars I have tried them in.
Looking back, I used Mobil 1 15W-50 pretty often in one of our old Civics. 10W-40 was the recommended oil for engine and transaxle, or at least it was near enough that I typically used it in all seasons. I used 10w30 every now and then, which I thought was daringly thin.
That little sewing machine was always fairly quiet, and it was mechanically smoother than the Accords, even with their balance shafts, probably because it displaced but 1.5 liters.

 

[Gary Allan]

Quote:
As you know, oils labeled as being of identical grade can have greatly different actual viscosities.


Sure, but suppose in the instances where this is reported the difference is only .2+/-.1 cSt or zero?

Quote:
My swag is that these oils probably contain similar levels of PAO.
GC is a very quiet oil in any application I've tried it in, while the M1 is certainly a little louder, because it is thinner than GC at any temeprature, and has lower HT/HS.


Ah (as said by some movie philosopher), but that would mean that M1 could only be/sound/feel different at the SAME temp. It will share just about every viscosity point from start up to full warm up that GC does ..at different times.

So, we cannot credit viscosity with this sensation (or lack of it) until full warm up.


Hey, I basically thought it was bunk, but then those links (which I didn't bookmark) showed up. They essentially stated that PAO's were noisier than the conventional base stocks.

 

[fdcg27]

Hmm, good point on the viscosity actually being the same at different points during warm-up for the two oils.
I think that most or all folks who have used both GC and Mobil 1 0W or 5w30 in the same engine would agree that GC yields quieter operation. The '99 Accord has seen at least a couple of runs of all three, while the '97 has seen a couple of runs of GC, as well as at least a few on Mobil 1 5w30, and I have always found GC to be quieter.
Can we then conclude that the explaination must be related to oil chemistry at some level more complex than basestock alone?

 

[SpitfireS]

smooth   /smuð/ Show Spelled [smooth] Show IPA adjective,-er, -est, adverb, verb, noun
–adjective
1.free from projections or unevenness of surface; not rough: smooth wood; a smooth road.
2.generally flat or unruffled, as a calm sea.
3.free from hairs or a hairy growth: a smooth cheek.
4.of uniform consistency; free from lumps, as a batter, sauce, etc.
5.free from or proceeding without abrupt curves, bends, etc.: a smooth ride.
6.allowing or having an even, uninterrupted movement or flow: smooth driving.

It looks like a smooth engine is an engine with less internal friction.
All but #3

(A smoother engine should produce more HP too?)
IMO it has to do with the oil film.

The range of HTHS in common oils is from 2.6 to 3.5, right?
That's a 35% difference (taking 2.6 as 100%)
Within grades the difference is...?
Lets say oil #1 has a HTHS of 3.0 and oil #2 a HTHS of 3.2
That's still a 6.6% difference.
Enough to have a change in oil film & smoothness?
If so then that's the answer.

 

[modularv8]

I have an '06 F150 5.4l that the engines shakes pretty rough at ~1700 rpms and then again at 2200 rpms. I recently took it into the dealership to have the rear differential checked and they noted that the engine idled rough. It also has a "rattle-like" sound upon light acceleration that I'm confident is one or two lifters.

Anyway I've obscessed about the roughness and rattle since I bought the truck new. It has always had oil changes at the dealership until a recent UOA showed what look like diesel oil. I lost all confidence with the dealer and did my first oil change at 33k with Motorcraft 5w20 blend. I'm a big believer in Motorcraft oil, but truck still ran rough and makes the same rattle. However, early morning piston slap was completely gone and it ran a little smoother after this oil change.

Last week, I changed the oil again and sent off the used oil for an UOA. I decided to go with full synthetic because there was slight consumption (first time this happened) on the MC 5w20 (~1/4 qt.) I put Quaker State Horsepower 5w20 full synthetic in it. And amazingly and in disbelief, the truck runs smooth even at the previously stated rpms. In addition, the rattle (lifters) is completely gone. I ran the truck along a wall at a nearby shopping center to hear any sounds and it is completely gone.

I don't know about other vehicles, but I have always believed the roughness in my truck comes from the Variable Cam Timing system that operates off oil pressure. For some reason the synthetic oil makes it operate smoothly. It's like a different truck.

 

[Ben99GT]

Originally Posted By: modularv8
It also has a "rattle-like" sound upon light acceleration that I'm confident is one or two lifters.


In a 5.4 3V? It's more likely the cam phasers, not the lash adjusters. If it's a rattle that occurs at lower rpm under light to moderate load, you can bet that's what it is. It's a pretty well known issue, one that my Uncle's '06 experienced, albeit his engine is pretty varnished/lightly sludged at less than 100K. I put Ultra 5W-20 in his truck to see if it can tackle the sludge, if it doesn't I'll talk him into a few changes with Red Line 5W-20.

You might want to check out Pennzoil Ultra, it has high levels of boron similar to MC.

 

[modularv8]

Yes, the 3v. The rattle I'm almost sure is a lifter or two under light load. As for the roughness, I think comes from the VCT/phasers. Does anyone else have roughness (engine shake) at around 1700 rpms? I have seen others post on the web the same thing, so I think its common to this engine. Anyway, mine seems to be gone and hope it stays that way. As a side note, the engine shake/roughness did not go away immediately after the oil change but after a few days engine operation.

 

[Wilhelm_D]

Originally Posted By: Jim Allen
Or rougher?

So many people on this board now offer anecdotal comments that a particular oil brand or viscosity grade makes their engine "smoother" or "rougher" or "more quiet" or "noisier." I'd very much like to know the science behind these comments.


The only science is actual viscosity (note, actual measured viscosity, not nominal viscosity).

The rest of it is imagined.

 

[orlzx6r]

Originally Posted By: ARCOgraphite
Clap your hands in Air at STP, then clap your hands underwater at 3 meters depth. Thats the difference between a 0w-20 and a SAE 50 1/2 way through engine warmup. Now add some fine gradations between the two extremes.


Next time when I want to measure my engines noise level, I'll be sure to clap my hands in the air and then underwater.


Only from arco...

 

[Wilhelm_D]

Originally Posted By: orlzx6r
Next time when I want to measure my engines noise level, I'll be sure to clap my hands in the air and then underwater.


Be sure to click your heels together and repeat "There's no place like home, there's no place like home."

 

[sl1driver]

Originally Posted By: Jim Allen
Or rougher?

So many people on this board now offer anecdotal comments that a particular oil brand or viscosity grade makes their engine "smoother" or "rougher" or "more quiet" or "noisier." I'd very much like to know the science behind these comments.

I admit to being a doubter, especially on the rough or smooth aspects (I can see where viscosity might make a difference with noise) but I'm willing to be convinced if someone can come up with convincing information.

Conversely, if someone has info counter to that, let's hear it.

I sincerely hope this doesn't degrade into an utterly useless, bandwidth-wasting, feelings-hurting urination contest.

For myself, I honestly cannot think of how one oil or another can make an engine smoother or rougher.


Smoothness doesn't change for me. However, I have noticed a slight difference in noise with different oils. I have no favorite oil, and I always buy it on sale, so I don't have any dogs in that fight.

But...don't be so quick to dismiss the concept of "butt dyno." If someone knows their vehicles really well, it certainly is conceivable that that person may be able to detect changes in how the engines perform, i.e. noise, smoothness, fuel economy, etc. It most certainly is plausible.

 

[Jim Allen]

Originally Posted By: modularv8
Yes, the 3v. The rattle I'm almost sure is a lifter or two under light load. As for the roughness, I think comes from the VCT/phasers. Does anyone else have roughness (engine shake) at around 1700 rpms? I have seen others post on the web the same thing, so I think its common to this engine. Anyway, mine seems to be gone and hope it stays that way. As a side note, the engine shake/roughness did not go away immediately after the oil change but after a few days engine operation.


I have an '05 F-150 5.4L 3V that's smooth as glass and has been that way from day one ( I bought it at 7K, it now has 24K). Noisewise, I have no complaints. It's got RP 5W20 in it right now, the second fill of it that will go at least 8K and maybe 10.

Going back to the original question, I have read some fancy technical terms bandied about here, but am not convinced those who uttered them really understand what they mean because there was little detailed explanation nor references ( : < ). Don't mean that as an insult and please note I smiled when I said it! No matter what, I'm grateful to have some search terms for my own research. I started this not even knowing what words to apply to the concept.