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Fuel dilution's effect on oil viscosity etc
#4778075
06/05/18 10:18 AM
06/05/18 10:18 AM
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Joined: Apr 2018
Posts: 619 Canada
nap
OP
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OP
Joined: Apr 2018
Posts: 619
Canada
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Re: Fuel dilution's effect on oil viscosity etc
[Re: nap]
#4778138
06/05/18 11:37 AM
06/05/18 11:37 AM
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Joined: Feb 2003
Posts: 7,981 Jupiter, Florida
Cujet
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Joined: Feb 2003
Posts: 7,981
Jupiter, Florida
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The elephant in the room is not just the raw fuel dilution. It's not unusual for most of the the fuel in the oil to evaporate, leaving behind various additives and heavier components of fuel. It's entirely possible, for example, to start and end with 5 quarts in the sump. 5 quarts of oil at the start, and 4.5 quarts of oil at the end, along with 1/2 quart of contaminants.
A great example of this would be the diesel "veggie" fuel users. The sumps are seriously contaminated with waste veggie oil. Often leading to oil failure and engine failure.
Last edited by Cujet; 06/05/18 11:39 AM.
People who count on their fingers should maintain a discreet silence.
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Re: Fuel dilution's effect on oil viscosity etc
[Re: nap]
#4778143
06/05/18 11:45 AM
06/05/18 11:45 AM
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Joined: Feb 2003
Posts: 7,981 Jupiter, Florida
Cujet
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Joined: Feb 2003
Posts: 7,981
Jupiter, Florida
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FYI, aircraft operators in very cold climates used to dilute the oil with fuel intentionally. This reduces viscosity for easy starting in severe cold. The fuel evaporates rather quickly after start, and oil pressure and temperatures remain normal.
In fact, some aircraft had a built in system, from the factory, that added fuel to the oil for cold weather starting. The requirement was that the oil reach 100 degrees F prior to takeoff.
People who count on their fingers should maintain a discreet silence.
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Re: Fuel dilution's effect on oil viscosity etc
[Re: Cujet]
#4778176
06/05/18 12:31 PM
06/05/18 12:31 PM
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Joined: May 2013
Posts: 2,169 Saskatchewan, Canada
Johnny2Bad
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Joined: May 2013
Posts: 2,169
Saskatchewan, Canada
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FYI, aircraft operators in very cold climates used to dilute the oil with fuel intentionally. This reduces viscosity for easy starting in severe cold. The fuel evaporates rather quickly after start, and oil pressure and temperatures remain normal.
In fact, some aircraft had a built in system, from the factory, that added fuel to the oil for cold weather starting. The requirement was that the oil reach 100 degrees F prior to takeoff. First of all, an airplane engine is not an automotive engine. It is a mistake to assume they are similar enough that various conditions or systems are interchangeable. The airplane engines that did use fuel to dilute engine oil have sumps that are much, much larger than a typical automobile, or at least a typical post-WWII automobile. As in sump capacity is measured in gallons, not quarts. Aviation oils in general are higher viscosity than automotive oils, for example Aeroshell 100 is equivalent to SAE 50 automotive viscosity. Aviation oils until relatively recently had no winter rated oils and no multigrade oils that were legal to use, so using fuel dilution was not a 'good practice", it was the only possible practice to adjust viscosity. By far the more common method of starting in cold weather is to tarp up the nacelle and provide heat under the tarp. The use of the equivalent of a campfire was hardly unheard of. The automotive equivalent is to tarp up the engine compartment and run exhaust from another running vehicle under the tarp to heat up the engine / sump, ground clearance being what it is making open fires difficult. If you've never had to do either to an aircraft or a vehicle, you haven't been in a cold start situation that would benefit from oil dilution via fuel either.
'57 FL Straight 50 wt '90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40] '96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50] '01 PT Cruiser [Mobil1 0W-40]
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Re: Fuel dilution's effect on oil viscosity etc
[Re: Johnny2Bad]
#4778208
06/05/18 12:58 PM
06/05/18 12:58 PM
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Joined: Dec 2005
Posts: 10,722 Upper Midwest
kschachn
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Joined: Dec 2005
Posts: 10,722
Upper Midwest
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Aviation oils until relatively recently had no winter rated oils and no multigrade oils that were legal to use, so using fuel dilution was not a 'good practice", it was the only possible practice to adjust viscosity. But multi-grade oils have been available to GA for over 30 years and manufacturers have approved their use in via service bulletins, right?
1994 BMW 530i, 241K 1996 Honda Accord, 267K 1999 Toyota Sienna, 409K 2000 Toyota ECHO, 280K
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Re: Fuel dilution's effect on oil viscosity etc
[Re: nap]
#4778238
06/05/18 01:25 PM
06/05/18 01:25 PM
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Joined: Mar 2017
Posts: 7,618 ...
PimTac
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Joined: Mar 2017
Posts: 7,618
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Why? What’s going to happen to it?
Cannot see signatures any longer so it doesn’t matter.
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Re: Fuel dilution's effect on oil viscosity etc
[Re: Johnny2Bad]
#4778627
06/05/18 09:01 PM
06/05/18 09:01 PM
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Joined: Dec 2009
Posts: 26,579 Regina, Saskatchewan, Canada
Garak
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Joined: Dec 2009
Posts: 26,579
Regina, Saskatchewan, Canada
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Aviation oils until relatively recently had no winter rated oils and no multigrade oils that were legal to use, so using fuel dilution was not a 'good practice", it was the only possible practice to adjust viscosity. Well, you could use a heater, or even better, heated storage, but ask the Regina Flying Club what they charge for heated hangar space. 
Plain, simple Garak.
2008 Infiniti G37 - Shell ROTELLA T6 Multi-Vehicle 5w-30, Wix 57356 1984 F-150 4.9L - Quaker State GB 10w-30, Wix 51515
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Re: Fuel dilution's effect on oil viscosity etc
[Re: Johnny2Bad]
#4779651
06/06/18 08:34 PM
06/06/18 08:34 PM
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Joined: Feb 2003
Posts: 7,981 Jupiter, Florida
Cujet
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Joined: Feb 2003
Posts: 7,981
Jupiter, Florida
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First of all, an airplane engine is not an automotive engine. It is a mistake to assume they are similar enough that various conditions or systems are interchangeable.
The airplane engines that did use fuel to dilute engine oil have sumps that are much, much larger than a typical automobile, or at least a typical post-WWII automobile. As in sump capacity is measured in gallons, not quarts.
Aviation oils in general are higher viscosity than automotive oils, for example Aeroshell 100 is equivalent to SAE 50 automotive viscosity. Thin straight viscosity oils were allowed in cold weather ops. Lycoming aircraft engines can use a straight 20 below 10F. Furthermore, many light aircraft hold 6 quarts, much like automotive applications. The little bit of Alaska ops I've done include using thin oils, preheating and there was near universal talk of using fuel to dilute. My point was simply that it was a procedure for cold weather ops. Not that it is good.
People who count on their fingers should maintain a discreet silence.
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