05 CRD Biodiesel and miles/gallon indicator

[emiperformance]

I am currently running B50 and noticed that my average miles /gallon indicater is way off to the point that when I am at a stop sign, the miles per gallon start to decend.
when I stop, it will show 26.5 miles per gallon, after a 5 minute stop, it showed 14.9 miles per gallon, what would cause it to go down if the car is not moving?
It never did this before.


Any info would help...


Danny

 

[maureen58]

mileage

When did you reset your mpg indicator? When you stop, you are still burning fuel but not putting on any mileage. If you just reset your mpg then you will see a fast decline, if you have say 300 mile on the reset it won't go down as fast. One thing nice about the CRD is that it will burn only 1/4 the fuel at idle as a gas engine.

 

[emiperformance]

I resetted it about 5 miles before I stopped.

 

[cowcatcher]

The reset is the reason. It will vary a lot after a reset. Leave it be for a couple of tanks or for a whole trip that takes a tank or so.

 

[kjpilot]

Yes it was the period of time from the reset that was the issue. the read out is an average MPG since the time you push the reset button up to the time you look at it. If the engine is running (burning fuel) but the car is not moving , the computer registers that as 0 MPG - you burned a gallon, but went nowhere , therefore you got 0 MPG. That period of time gets averaged in with the rest.

So if you reset the computer, and got 26 MPG for 5 minutes, then stopped to let it idle (0 MPG) for 6 minutes your average would be 11.8 MPG.

That being said, there may be an efficency issue with the biodeisel based on chemistry. I don't know much about biodiesel, but I am familiar with Ethanol.

Ethanol produces around 50% less energy than gasoline, therefore it takes twice as much ethanol to move the same mass, the same distance, at the same speed. No one burns 100% ethanol, it's usually 10% ethanol, 90% gasoline- so the efficiency issue is lowered to 5%. If you get 20 MPG with pure gas, you'll get 19 with 10% ethanol.

I don't know what the difference between diesel & biodiesel is, but I would not be suprised if they are about the same as gas/ethanol, because in both cases were talking petroleum/corn. So at 50% BD you might experience a 25% hit. Again, based on my knowledge of ethanol, not biodiesel!

 

[VTNomad]

MPG

Your miles per gallon will always decrease when sitting still. Because you are averaging in 0 miles while the engine is still using some fuel.

 

[emiperformance]

this is true, but if I reset the meter to "0" when not moving, then idle for about a block, it will climb to 99.9. My dodge caravan does not to it.
on my van, the counter stops when I stop and does not decline.
maybe the biodiesel is throwing off the censer since the viscoty is different.

who knows...


Thanks again,
Danny

 

[kjpilot]

The major difference s that you are moving, therefore you are getting some miles in while you burn the fuel. Your Caravan technically should do the same thing, but for some reason does not.

 

[valkraider]

Biodiesel will not throw off the sensor....

I have 60k miles using biodiesel in my VW TDI and 8000 miles using biodiesel in my CRD.

100% Biodiesel has about 5% less BTU than petroleum diesel. But biodiesel is higher cetane and has more lubrocity, which offset that somewhat.

Results vary based on the type of engine, but generally:

With B20 you will not have any difference in mileage.
With B50 you will probably see around 1% less mileage.
With B100 you will probably see around 3% less mileage.

Honestly, I have not measured any difference in mileage using B100 (or B99 as they sell now for tax purposes) and petroleum diesel. Well, to be absolutely honest that is in my TDI volkswagen, because in my CRD I have never used anything less than B20 biodiesel since the first tank from the dealer which was B5 biodiesel...

Depending on the engine and fuel quality in your area - some people see increases in mileage with B20 because of the added cetane and lubrocity.

There are also mathematical physics models that claim biodiesel will give you slightly more torque due to a slightly longer burn cycle providing force longer in the cycle... But these are highly theoretical...

I have found that my EVIC mpg is a mile or two low - when I compare the EVIC readouts to mileage calculations based on fuel consumption....

And since the Liberty has no "instant" mileage readout - the best you can do is to reset the "average" indicator which will give you a pretty good "instant" for a mile or two... The longer since the last reset - the slower the average value will change. Stopped at a stoplight you are getting 0mpg.

 

[valkraider]

I don't know what the difference between diesel & biodiesel is, but I would not be suprised if they are about the same as gas/ethanol, because in both cases were talking petroleum/corn.

Biodiesel is not made from corn. Biodiesel is made from vegitable oil. Which can be soy based, or canola based, or even algae based. The oil can also be recycled waste vegitable oil, like from deep-fryers... In the USA the soy lobby is very strong so much of our biodiesel is made from soy oil, which has one of the lowest yeilds of any plant. Canola and Rapeseed have a higher oil yeild, and algae has an oil yeild many many times that of soy.

Also, Ethanol is not exclusively made from corn. It can be made from any plant matter that contains sugars. In the USA the corn lobby is very strong, and is why we use mostly corn for ethanol. Although cellulosic ethanol is catching on pretty well, which is making ethanol from waste plant matter... In Brazil they have more sugar cane than corn and use it to make ethanol as it has a higher yeild than corn.

Corn and Soy are low yeild. If our future lies with biofuels - cellulosic ethanol and algal biodiesel are the directions we need to look. But they are both young technologies - so the corn and soy based fuels are a good first step...

 

[cowcatcher]

I have only run one tank of B20. That was when new and cold. My mileage dropped of about 2 MPG but that was not a good test. I only have one source here and it is a special test for a local school bus fleet DOE program. That was suspended in mid winter for failure from fuel clouding and engine stalls. The source is hard to get to, the fuel is 20>40 cents per gallon more and the yard is dirty and unpaved so I have not been back.

I understand that Castor beans may be about the highest production source and are more aclimated to dry, non irrigated, non mid-west climates.

 

[JeepJeepster]

this is true, but if I reset the meter to "0" when not moving, then idle for about a block, it will climb to 99.9. My dodge caravan does not to it.
on my van, the counter stops when I stop and does not decline.
maybe the biodiesel is throwing off the censer since the viscoty is different.

who knows...


Thanks again,
Danny

Its normal, my 04 gaser does it, our 94 grand does it, its normal. O

 

[kjpilot]

Biodiesel is not made from corn.

Also, Ethanol is not exclusively made from corn. It can be made from any plant matter that contains sugars. In the USA the corn lobby is very strong, and is why we use mostly corn for ethanol. Although cellulosic ethanol is catching on pretty well, which is making ethanol from waste plant matter... In Brazil they have more sugar cane than corn and use it to make ethanol as it has a higher yeild than corn.

As far as the bio diesel goes, I recieved a brief education on what it is & where it comes from since my post above. In my defense, I admitted my lack of knowledge of biodiesel 8-[

As far as ethanol, I knew it came from other sources than corn, but since I live in Minnesota, everything is corn! My complaint about ethanol is not the yield of fuel from the source, but the yield of energy from the fuel. that won't change much. The only advantage to ethanol is it is produced domestically from a renewable resource. There is no other advantage in it's production or it's use, and in some cases, ethanol can be detrimental.