Oil dilution doesn't appear to work

[pierscockey]

Hi

I don't know if I'm doing something wrong, but I can't get it to work in the same way it does in various You Tube tutorials.  Pressing it doesn't appear to make the oil pressure drop in any meaningful way.

I've attached a track which shows 2 cold starts.  One pretty much constantly holding the button down, and the next not doing it at all.  All I'm doing is increasing the boost to keep the oil pressure at 120psi.  Both take exactly the same time to get the water temp up to 60c.

oil_dilution.trk

Edited November 1, 2024 by pierscockey

[jackill]

I believe that this is removed from aircraft right now - I can’t even open the button cover. I will post video later. 

[pierscockey]

1 hour ago, jackill said:

I believe that this is removed from aircraft right now - I can’t even open the button cover. I will post video later. 

It's quite tricky to open, but you can.  You need to click to the left of the cover as you're looking down at it.  Or you can bind a key.

[jackill]

3 hours ago, pierscockey said:

It's quite tricky to open, but you can.  You need to click to the left of the cover as you're looking down at it.  Or you can bind a key.

You are right, you need to click much more to the left than center of the cover.

Regarding dilution I have the same observation - no real effect over oil pressure (I tested in -10*C). I recall some other discussion on this forum, that oil dilution was used before engine shutdown and effect during engine startup is not correct. However there was no mention in changelog.

[pierscockey]

Glad I’m not the only one!  All I know is it definitely used to do something, and it’s quite important for Reflected’s Beware campaign in order for speedy start up so as to not be left behind by the squadron. 

[Terry Dactil]

Our friendly ChatGPT confirms that that oil dilution is not recommended for startup, but is intended to be used on the previous shutdown.

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Oil dilution on Rolls-Royce Merlin aircraft engines should generally be done *prior to shutdown* in preparation for cold weather. This procedure involves injecting a small amount of fuel into the oil system to lower the oil’s viscosity, helping prevent it from becoming too thick in cold conditions.

Here’s why it’s best done before shutdown:

1. **Prevents Oil Thickening Overnight:** By diluting the oil before the engine is stopped, the oil mixture stays less viscous, making it easier to start the engine the next day or during subsequent flights in cold weather.

2. **Easier Start-up in Cold Conditions:** The diluted oil makes it easier for the engine to crank in freezing temperatures, as it flows better and lubricates engine components sooner.

3. **Reduces Battery Strain and Engine Wear:** A lower oil viscosity on a cold start reduces the strain on the starter motor and battery and minimizes the wear on engine components, since the oil can circulate faster.

4. **Alternative Methods at Start-up Are Limited:** While oil dilution at startup can theoretically improve flow, starting the engine in cold weather without prior dilution puts significant strain on the system.

In practice, dilute the oil for cold weather *before shutting down* after a flight if freezing temperatures are expected. This way, the engine will be prepped and ready for an easier start-up.

[pierscockey]

Thanks for the replies chaps.

Not sure how I didn’t find this previous bug report on the same topic when I searched yesterday 

 

Seems it’s been this way for a while, but definitely changed behaviour from when Reflected made his video.  
 

Haven’t tried diluting before startup as Nineline did, so will give that a go a bit later.  

[Dragon1-1]

11 hours ago, Terry Dactil said:

Our friendly ChatGPT confirms that that oil dilution is not recommended for startup, but is intended to be used on the previous shutdown.

It does not "confirm" a single damn thing. As a rule, don't ask AI about anything specialist, it spews BS way too often, and the more specialized the subject, the more often it's wrong. When it's correct, it's by accident.

The real reason that oil dilution is applied before shutdown is completely unrelated to any of the above. You have to remember that you're injecting fuel into the oil sump. Fuel burns, and much more easily than oil does, at that. As such, it was recommended to idle the engine until the oil temperature got below 100F before applying the diluter. In theory, in a hot engine, the fuel will evaporate. In practice, the oil sump would occasionally catch fire if that rule was not followed. Injecting the fuel on startup, when the engine was warming up, not cooling down, would have a greater risk of fire.

[jackill]

I tested at 5*C, warming up at 1200 RPM. First try without dilution, second one holding dilution form engine start. After 3 minutes pressures were almost identical if not the same.

Topic is also noticed here: 

 

Edited November 7, 2024 by jackill