My imagination?

[demarpaint]

Originally Posted By: OVERK1LL
Well, the gear ratio of your transmission changing because you changed your engine oil isn't one of those things. I believe that is why people are laughing.

It is more likely a variance in the tach.


+1 rpms will be the same in the same gear at the same speed. They can increase if the transmission is slipping, but all things being equal they aren't going to decrease (same speed/same gear). Yes changing to a thinner grade oil, or synthetic oil, using a UCL, increasing tire pressure can increase mpgs.

 

[BigNick]

Theoretically speaking...
You're driving east, at oh.. let's say.. 69mph. All of a sudden, the weather changes, and you are now driving into a 30mph westerly wind.

For your car to maintain the 69mph you have your cruise set at, you don't think that there would be some change in RPM's (most likely slightly increased) so that the car can maintain that speed?

That is just my thinking... There are other variables, however small, that can slightly change RPM's at a certain speed. It's not just "gear ratios"...

 

[BuickGN]

Originally Posted By: BigNick
Theoretically speaking...
You're driving east, at oh.. let's say.. 69mph. All of a sudden, the weather changes, and you are now driving into a 30mph westerly wind.

For your car to maintain the 69mph you have your cruise set at, you don't think that there would be some change in RPM's (most likely slightly increased) so that the car can maintain that speed?

That is just my thinking... There are other variables, however small, that can slightly change RPM's at a certain speed. It's not just "gear ratios"...


With the convertor locked it is just a matter of gear raios, nothing else, no other variables.

Even if it isn't locked, explain why you would see less rpms with a thinner oil on the same stretch of road at the same speed....

 

[mechtech2]

Like mentioned, oil does NOT change your mechanical gearing.

And 3 MPG better due to changing to another oil of the same viscosity? When the engine oil is such a small contributor anyway?

The reason that car Mfrs. and private testing does not reveal these 'truths' is that they are impossible.

 

[OVERKILL]

Originally Posted By: BigNick
Theoretically speaking...
You're driving east, at oh.. let's say.. 69mph. All of a sudden, the weather changes, and you are now driving into a 30mph westerly wind.

For your car to maintain the 69mph you have your cruise set at, you don't think that there would be some change in RPM's (most likely slightly increased) so that the car can maintain that speed?

That is just my thinking... There are other variables, however small, that can slightly change RPM's at a certain speed. It's not just "gear ratios"...


I turn a ratchet on a bolt 1 rotation. It required 100lb-ft to move that bolt 1 rotation.

I turn a ratchet on another bolt 1 rotation. It required 150lb-ft to move that bolt 1 rotation.

How many rotations did we move again?

We are dealing with gears, not a CVT, with the converter locked, that is all we are dealing with. If this was a CVT, your point would have merit, but with a tradition gear-driven transmission, this is simply not the case. Regardless of force applied, 1 rotation is one rotation, 2,500RPM is 2,500RPM, and whatever that works out to at the wheels in terms of RPM and subsequent speed in MPH is going to remain the same UNLESS:

1. Your converter is not locked
2. Your converter is SLIPPING
3. Your transmission is SLIPPING

None of which would have been affected in ANY way by the change of the viscosity of the oil you are running in your engine.

 

[demarpaint]

Originally Posted By: BigNick
Theoretically speaking...
You're driving east, at oh.. let's say.. 69mph. All of a sudden, the weather changes, and you are now driving into a 30mph westerly wind.

For your car to maintain the 69mph you have your cruise set at, you don't think that there would be some change in RPM's (most likely slightly increased) so that the car can maintain that speed?

That is just my thinking... There are other variables, however small, that can slightly change RPM's at a certain speed. It's not just "gear ratios"...


If a transmission is operating correctly, and the TC is locked or the clutch is not slipping the only thing that happens in a head wind is mpgs decrease in order to maintain speed. Lets say at 60 mph my tach is reading 2200 rpm in OD. I get hit by a 30 mph headwind, rpms drop, speed drops. I give it more gas, my rpms increase, my speed increases back to 60 mph and 2200 rpms. The only change is the mpgs go out the window because I need more gas to maintain speed. It's a lot easier to see this unfold driving a stick with a good clutch.

 

[BigNick]

Originally Posted By: BuickGN
With the convertor locked it is just a matter of gear raios, nothing else, no other variables.
Even if it isn't locked, explain why you would see less rpms with a thinner oil on the same stretch of road at the same speed....
I have NO idea how/why I noticed this. I'm just saying, all variables remained almost equal, EXCEPT for the synthetic oil.

Originally Posted By: demarpaint
If a transmission is operating correctly, and the TC is locked or the clutch is not slipping the only thing that happens in a head wind is mpgs decrease in order to maintain speed. Lets say at 60 mph my tach is reading 2200 rpm in OD. I get hit by a 30 mph headwind, rpms drop, speed drops. I give it more gas, my rpms increase, my speed increases back to 60 mph and 2200 rpms. The only change is the mpgs go out the window because I need more gas to maintain speed. It's a lot easier to see this unfold driving a stick with a good clutch.
I'm sorry, this doesn't make sense to me. If I all of a sudden start driving into a continuous head wind, it's logical to think that my engine would have to "work harder" to maintain the same speed before I hit this continuous head wind. How else would this be achieved other than by increasing RPM's?

Eg #2 Different scenario: All variables remain equal while in cruise control, when all of a sudden you begin on a continuous stretch of highway with a 15 degree incline. Your engine will have to "work harder" to maintain that set speed, and you will see your RPM's increase (as this is the only way an engine can "work harder" righ???
I'm no engineer. I'm open to opinions/statements. Just trying to understand something, that may have more than one explanation. I noticed something, i.e. the decrease in RPM's, after changing what I believe is only ONE variable (switch from dino to synth), and I agree that it may not be exactly correct and more likely more complicated than that.
Nice to have some detailed explanations besides people just replying by laughing, and not explaining anything. I have to admit, I'm still not convinced or agree to everything said, but appreciate the good responses to the discussion!

PS: Think of this also: Not saying it is totally correct, but just think about it... Assume that ONE variable changed, leads to a decrease in RPM's to maintain the same speed ... Doesn't this explain the increase in MPG??? ---> The pistons spin 50-75 RPM's less per minute, hence you have less explosions in the chambers per minute, hence you burn less gas per minute, hence your MPG increase! ... haha makes sense to me! haha
Again, wide open to suggestions/opinions/engineering 101.

 

[BuickGN]

Imagine you're riding your bike. You encounter a hill. You don't downshift, you keep it in the same gear. You pedal harder (opening the throttle more)to keep it at the same speed. You wouldn't expect the pedals to spin faster in the same gear at the same speed just because you're pushing harder, would you? It's the same with the car. The engine is mechanically linked to the wheels. Unless you have a trans slipping, it's impossible for rpms to vary for a given speed in a given gear with the convertor locked.

 

[OVERKILL]

Originally Posted By: BigNick
I'm sorry, this doesn't make sense to me. If I all of a sudden start driving into a continuous head wind, it's logical to think that my engine would have to "work harder" to maintain the same speed before I hit this continuous head wind. How else would this be achieved other than by increasing RPM's?


Your engine "works harder" by consuming more air and fuel. RPM does not have to increase, and in the example cited, would not if the speed remains the same.

Quote:
Eg #2 Different scenario: All variables remain equal while in cruise control, when all of a sudden you begin on a continuous stretch of highway with a 15 degree incline. Your engine will have to "work harder" to maintain that set speed, and you will see your RPM's increase (as this is the only way an engine can "work harder" righ??? div>


How hard an engine works is related to load. This is not directly related to RPM. While an engine can make more power, and subsequently perform more work at a higher RPM, load can be applied at any RPM, and subsequently more fuel and air are required to handle that load and maintain that RPM.

Quote:
I'm no engineer. I'm open to opinions/statements. Just trying to understand something, that may have more than one explanation. I noticed something, i.e. the decrease in RPM's, after changing what I believe is only ONE variable (switch from dino to synth), and I agree that it may not be exactly correct and more likely more complicated than that.
Nice to have some detailed explanations besides people just replying by laughing, and not explaining anything. I have to admit, I'm still not convinced or agree to everything said, but appreciate the good responses to the discussion!


BuickGN's example of a bicycle should hopefully make it clear for you.

Quote:
PS: Think of this also: Not saying it is totally correct, but just think about it... Assume that ONE variable changed, leads to a decrease in RPM's to maintain the same speed ... Doesn't this explain the increase in MPG??? ---> The pistons spin 50-75 RPM's less per minute, hence you have less explosions in the chambers per minute, hence you burn less gas per minute, hence your MPG increase! ... haha makes sense to me! haha
Again, wide open to suggestions/opinions/engineering 101.


The pistons don't spin

They move up and down in the bores; the crankshaft spins via the force applied through the rods, which connect to the pistons, which are pushed down their bores through the process of combustion.

An engine can consume LESS fuel at a higher RPM; high load at low RPM will cause the engine to ingest more air and fuel to maintain that RPM than an engine spinning at a higher RPM under low load, where the opposite is the case.