Wiith rising fuel prices, running 20% RUG in summer (and 40% in winter) is becoming expensive..
Instead of mixing the WMO some people run a 2-tank setup, but then you will be consuming diesel to warm up the car. Approx 5 gallons per month for my situation I calculated.
(Say 10min to warm it up, avg. speed 30mph, 40mpg (car will be using more when cold but let's not go into that much details). In 10min you will do 5miles, so 0.125gal per trip. Driving to work 4weeks, 5 times per week, 2trips per day means 5gal)
Also 2 tank system adds complexity, another tank to fill, need to switch before turning off car.
So then the third option I thought of is an electric pre-heater. Here some calculations, to prove it if it's theoretically possible. I'll be using the metric system cuz its easier;
1. What is achieved by 20%/40% RUG (summer/winter)
- Gasoline viscosity is approx 0.75 cSt at 20C / 60F: https://www.engineeringtoolbox.com/kinematic-viscosity-d_397.html, at 0C I couldn't find but say its 3
- Motoroil (10W40) is approx 250 cSt @ 20C and 1000 cSt @ 0C. See "motoroil_cst" attachment.
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20% Rug blend @ 20C: +- 60 cSt
40% Rug blend @ 0C:+- 50 cSt
So we obtain 55-ish cSt. This is in the right ballpark as literature explains 10-15 cSt (but this is marine diesel direct injection, I use IDI, which is more forgiving, needs less pressure, etc)
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2. What temperature do we need the oil to be at?
Extrapolating data, says approx 45-50C (or 120F) to lower 10W40 viscosity to acceptable range 50-60 cSt (see temp.png)
This can be achieved by using heat from engine coolant, but that will be cold at coldstart. So can we use electric heating?
3. What kind of electric heating do we need to heat the oil?
Before we calculated that we need 0.125gal in order to heat the engine to operating temperature. After that we can use coolant heat.
0.125gal = 0.5liters WMO. And we must heat that to 50C. Some more info's:
- Specific heat of oil is approx 2.0 kJ/kg/C (https://www.researchgate.net/figure...nts-as-function-of-Temperature_fig1_326488375)
- 0.5l wmo is approx 0.425kg
Two scenario's:
a. freezing outside (-10C). From -10 to 50 is 60C of heating
b. normal temp (20C). From 20 to 50 is 30C of heating
In order for the car to start fuel needs to be at right temp. So say you have 0.425kg of fuel in the red part of the fuel system (filter, pump, ...; see preheated_circuit).
- At -10C, if you allow it to warmup for 2.5 minutes, you will need 0.425×2×60×1000 ÷ (2.5×60) = 340W
- At 20C, if you allow it to warmup for 1 minute, you will need 0.425×2×30×1000 ÷ (1×60) = 425W
4. Conclusion
So you will be looking at a ballpark of +- 1kW of heating considering all the heat losses and other inefficiencies. Possibly reducible to 100W if :
- Better insulation (so less heat losses, say cut by 50%)
- Decrease fuel-amount in red part of circuit (say also 50%)
- If you can get away with heating it only to 40C instead of 50C (1 - 40/50 = 20% decrease in energy needs), viscosity would be 60-75ish.
- Willing to wait longer (5 min at -10C, 2.5min at 20C, 50%)
1000 * 0.5*0.5*0.2*0.5 = 25 watt, which is in the 100W ballpark range
100 to 1000W heaters are available, so I will be attempting this. I'll keep you posted.
Instead of mixing the WMO some people run a 2-tank setup, but then you will be consuming diesel to warm up the car. Approx 5 gallons per month for my situation I calculated.
(Say 10min to warm it up, avg. speed 30mph, 40mpg (car will be using more when cold but let's not go into that much details). In 10min you will do 5miles, so 0.125gal per trip. Driving to work 4weeks, 5 times per week, 2trips per day means 5gal)
Also 2 tank system adds complexity, another tank to fill, need to switch before turning off car.
So then the third option I thought of is an electric pre-heater. Here some calculations, to prove it if it's theoretically possible. I'll be using the metric system cuz its easier;
1. What is achieved by 20%/40% RUG (summer/winter)
- Gasoline viscosity is approx 0.75 cSt at 20C / 60F: https://www.engineeringtoolbox.com/kinematic-viscosity-d_397.html, at 0C I couldn't find but say its 3
- Motoroil (10W40) is approx 250 cSt @ 20C and 1000 cSt @ 0C. See "motoroil_cst" attachment.
Mixing viscosities | Widman International SRL
40% Rug blend @ 0C:+- 50 cSt
So we obtain 55-ish cSt. This is in the right ballpark as literature explains 10-15 cSt (but this is marine diesel direct injection, I use IDI, which is more forgiving, needs less pressure, etc)
How to deal with High Viscosity fuels?
The answer to the above question depends on how high is the viscosity of the fuel. Let us assume that the Bunker supplied has a Viscosity of 500 cSt instead o
mfame.guru
or
2. What temperature do we need the oil to be at?
Extrapolating data, says approx 45-50C (or 120F) to lower 10W40 viscosity to acceptable range 50-60 cSt (see temp.png)
This can be achieved by using heat from engine coolant, but that will be cold at coldstart. So can we use electric heating?
3. What kind of electric heating do we need to heat the oil?
Before we calculated that we need 0.125gal in order to heat the engine to operating temperature. After that we can use coolant heat.
0.125gal = 0.5liters WMO. And we must heat that to 50C. Some more info's:
- Specific heat of oil is approx 2.0 kJ/kg/C (https://www.researchgate.net/figure...nts-as-function-of-Temperature_fig1_326488375)
- 0.5l wmo is approx 0.425kg
Two scenario's:
a. freezing outside (-10C). From -10 to 50 is 60C of heating
b. normal temp (20C). From 20 to 50 is 30C of heating
In order for the car to start fuel needs to be at right temp. So say you have 0.425kg of fuel in the red part of the fuel system (filter, pump, ...; see preheated_circuit).
- At -10C, if you allow it to warmup for 2.5 minutes, you will need 0.425×2×60×1000 ÷ (2.5×60) = 340W
- At 20C, if you allow it to warmup for 1 minute, you will need 0.425×2×30×1000 ÷ (1×60) = 425W
4. Conclusion
So you will be looking at a ballpark of +- 1kW of heating considering all the heat losses and other inefficiencies. Possibly reducible to 100W if :
- Better insulation (so less heat losses, say cut by 50%)
- Decrease fuel-amount in red part of circuit (say also 50%)
- If you can get away with heating it only to 40C instead of 50C (1 - 40/50 = 20% decrease in energy needs), viscosity would be 60-75ish.
- Willing to wait longer (5 min at -10C, 2.5min at 20C, 50%)
1000 * 0.5*0.5*0.2*0.5 = 25 watt, which is in the 100W ballpark range
100 to 1000W heaters are available, so I will be attempting this. I'll keep you posted.
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