MoS2 testing - sound levels

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After experiencing very good results with MoS2 in a 1995 Miata, including reduced engine noise, increased engine smoothness throughout the rev range, and steady state fuel economy increases of 5-8%, I decided to try it in a couple of other vehicles despite being relatively biased against using additives without a significant reason for doing so.

Due to lots of weather variability where I live, I decided to just measure sound pressure levels using an older Radio Shack 33-2050 sound level meter. The two vehicles are a 1996 BMW with a 2.8 liter inline 6 and 130k miles, and a 2011 Corvette with a 6.2 liter V8 and 20k miles. Tests were done in my garage, with all garage doors opened in every instance. Because I live in a cul-de-sac, I ensured that it was quiet outside when I did the meausrements, and made sure that nothing in the garage such as the HVAC, were on.

I conducted the measurements by having someone else start up the car during cold starts, and held the sound level meter one foot above the centerline of the engine using a ruler. The hood was open fully and held open by the built-in prop struts. On cold starts, I let the engine speed settle for 3-5 seconds until a steady fast idle speed was atttained. For hot measurements, I simply drove into the garage, opened all the garage doors, and did the measurements myself, again using the one foot ruler as a guide. I did several tests before adding the MoS2 on various days and gained a baseline that fluctuated by a maximum of 1-2 db in every instance.

After adding the MoS2, each of the vehicles have been driven between 300-500 miles, and I personally ensured that some of this was during high RPM and high throttle opening driving. This was probably the most fun part of this testing.

Anyhow, here's what I got (hot measurements are without electric cooling fans being activated):

BMW cold:

Baseline: 82-84 db
After MoS2: 77-79 db

BMW hot:

Baseline: 74-76 db
After MoS2: 70-72 db

Corvette cold:

Baseline: 79-81 db
After MoS2: 75-77 db

Crovette hot:

Baseline: 73-75 db
After MoS2: 69-70 db

Both vehicles are driven inconsistently enough so that any fuel economy measurements would be pretty meaningless. The BMW is most noticeably quieter during cold starts. There's a lot of mechanical noise that isn't present any more. The Corvette motor, when hot, was quiet before but is no so quiet that a nrmal speaking voice is clearly able to be heard from someone standing on the other side of the open engine bay.

The BMW is pretty well insulated and I honestly don't notice any difference in sound or smoothness when driving the vehicle. The Corvette makes a lot of exhaust and engine noise and it's also impossible to hear any engine noise changes over that, but it does feel smoother as it revs, though that may be a placebo effect thing.

No oil was changed during this time, and the same gas has been used throughout. Temps have generally been in the 40's and 50's, and nothing has changed within our garage that might absorb sound. The same one foot ruler was used, and A-weighting was used throughout.
 
Very cool data. I applaud you for doing this.

Okay, so the engine is quieter. That is pretty obvious.

Any guesses on the "how or why" moly disulfide is making your engine quieter? For example, if the valve train is responsible for making a majority of the engine noise, because of moving metal parts coming in contact with eachother, or improper oil films being present at start-up, then how is moly plated onto these parts making the engine quieter at start-up and at normal operating temps?

I believe your data. I'm just curious that since we have data that clearly links the addition of MoS2 to decreased engine noise, is there any guesses as to how or why this is happening....
 
MoS2 simply works! I love the stuff and use it in everything I own with a ICE. Too bad I can't use it in my ATV or the kids dirt bikes tho...

I picked up a can the other day at NAPA and noticed the price has went up! $7.77 locally for a can! Still a deal for what it is!!
 
The data I've seen in that for every 3dbA increase in SPL, the noise doubles. Some use a 5dbA doubling but 3dbA is, to my knowledge, the most accurate.

With those SPLs, the engines are about half as noisy as they were before MOS2. That would be noticeable, as shown by being able to have a conversation where it wasn't really possible before.

In both my vehicles, they seem quieter and smoother with MOS2 but I didn't go all technical with a sound level meter
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Thanks for taking the time to do this!
 
Injured again,great idea and interesting method. Thanks for doing this. I know many here chirp(well maybe only a couple) about real world and scientific data and trying this with a sound level measuring instrument trying to maintain a consistent procedure is a great idea.
As far as why it lessens noise I think its because the mos2 plates the contacting metal parts insulating them from each other.

So this summer with mos2 in the sump I was getting up to 30mpg. Now I can't get it past 23 on the highway. I know winter gas costs a couple mpg but I've lost 7 since not adding any mos2 to this sump load of oil.
It's been a gradual decline. Didn't happen instantly. I'm about 5000 mikes into this interval with only cera tec in the oil.
I'm considering adding mos2 today just to see if it increases again.
Some people will never accept that an additive can help an engine in various ways and that's fine. I don't care what they believe nor do I care if they use it or not however of all the people I've turned in to mos2 not a single person has seen no benefit,whether it's mileage or ease of starting in -40 cold. Something improves.
Thanks for taking the time to do this injured again. Those of us who use it know it works,those who've chosen to bury their heads in the sand are missing out.
The 8 bucks a can it costs is recouped within the first tank or 2 of fuel.
I'll add some today and post here if I get any mpg back.
 
To respond to some of the posts, it did seem like quite a bit of db reduction, and the A weighting is supposed to represent th sensitivity curve of human hearing. But then I thought of threads I've seen where someone puts sound insulation in their vehicle and achieves a 3-5 db reduction in noise. To my ear, this seems to not quite be that much, but it is possible there are mechanical harmonics that trigger the sound meter that are masked by other noise, or just inaudible due to some problem with my hearing. It may also be that this consumer grade sound level meter has a non-linear response.

But I did recruit both my son and my wife to do the cold starts and both notice a difference standing next to the open engine bay, but neither said they really could distinguish a difference from inside while driving or riiding.

The idle speed did not change in either vehicle.

I guess it is not that much of a stretch to corelate reduced noise with friction reduction in the absence of other factors that could reduce noise. It might be a further stretch to correlate reduced friction to measureable decreases in fuel consumption, but I don't have accurate fuel mileage records for the BMW and won't be driving the Corvette much until the spring, by which time it will be really close to needing new tires that would invalidate any comparison anyway.

I'll keep measuring the sound levels in another few hundred miles to see if there's further decrease.
 
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Interesting, I noticed my Subaru got quieter and smoother on cold starts as well with the MoS2. This might confirm it. Very nice work!! I applaud your testing.
 
Originally Posted By: Injured_Again
To respond to some of the posts, it did seem like quite a bit of db reduction, and the A weighting is supposed to represent th sensitivity curve of human hearing. But then I thought of threads I've seen where someone puts sound insulation in their vehicle and achieves a 3-5 db reduction in noise. To my ear, this seems to not quite be that much, but it is possible there are mechanical harmonics that trigger the sound meter that are masked by other noise, or just inaudible due to some problem with my hearing. It may also be that this consumer grade sound level meter has a non-linear response.

This is understandable given the fact that, subjectively, a 2-3 dB change in sound level is barely perceptible to most human ears.
Nice work and thank you once again for your efforts Injured_Again!
 
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I'm pleasantly surprised that significant sound reductions were measured. I always assumed that people who said this additive reduced noise were imagining it. Thank you for your testing and writing it up! It would be great if other people also do similar testing.
 
Good to know it isn't in the heads of the people making the claims of a quieter engine.
 
Originally Posted By: demarpaint
Good to know it isn't in the heads of the people making the claims of a quieter engine.


It's pretty noticeable in the Miata because the engine is noisy and there's so little sound insulation, but in the other cars, it's really not noticeable that the engine is quieter. Maybe this is why some users don't believe the product works.

I originally was thinking of using a torque wrench to rotate the engine to see how much force it would take, but thought that method was too dependent on things I couldn't control, even as simple as the speed at which I tried to initiate rotation of the engine.

I took some noise readings in the Miata when driving on the same roads, but there's so much other noise that the sound levels didn't change even if the engine note and engine smoothness have noticeably changed. So, this seemed like the best way to determine any kind of operational change from the MoS2.
 
Originally Posted By: Injured_Again
Originally Posted By: demarpaint
Good to know it isn't in the heads of the people making the claims of a quieter engine.


It's pretty noticeable in the Miata because the engine is noisy and there's so little sound insulation, but in the other cars, it's really not noticeable that the engine is quieter. Maybe this is why some users don't believe the product works.

I originally was thinking of using a torque wrench to rotate the engine to see how much force it would take, but thought that method was too dependent on things I couldn't control, even as simple as the speed at which I tried to initiate rotation of the engine.

I took some noise readings in the Miata when driving on the same roads, but there's so much other noise that the sound levels didn't change even if the engine note and engine smoothness have noticeably changed. So, this seemed like the best way to determine any kind of operational change from the MoS2.


IMO it was a great idea and very hard to dispute.
 
Originally Posted By: Turk
Excellent.

Ok, naysayers, what say you??

Crickets, Chickets...



Did you have to do that? Now they'll be sure to come out. LOL
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