Don't mix biodiesel with diesel in your tank.

I'm getting confused from all of this....

It sounds like splash blending isn't recommended because it potentially isn't enough agitation to mix the B100 with diesel. However, is the problem only that in colder climates the B100 will gel if not properly mixed, or is the problem that in any climate there are potentially problems with water separation if not properly mixed?

Brian

From the posts, it almost sounds like both could be an issue.

famelec said:

I'm getting confused from all of this....

It sounds like splash blending isn't recommended because it potentially isn't enough agitation to mix the B100 with diesel. However, is the problem only that in colder climates the B100 will gel if not properly mixed, or is the problem that in any climate there are potentially problems with water separation if not properly mixed?

Brian

Click to expand...

Drive a few miles and your tank will be completely mixed because the IP returns a significant flow back to the tank. The water thing is a different (potential) issue.

Why is life so complicated

I can check my fuel filter for water - no problem, I'll do it - but is there anything bad about stratification other than possible gelling?

Would I be better off, if I want my life to be simple, in just deciding between petrol 100% or B100 (actually, B75 is what's being supplied at this time of year).

So far, I've been very happy with my routine of filling up when I hit half empty (or half full, depending on your personality) with a 1/4 tank of bio and a 1/4 tank of petrol. I've always figured that by filling up when I hit 1/2, I'm buffering against sudden changes in fuel composition.

Why is life so complicated?

And why, when I've been on this forum for over 2 years with numerous posts, am I still labeled as a newbie?

CarrboroTDI said:

I can check my fuel filter for water - no problem, I'll do it - but is there anything bad about stratification other than possible gelling? NO, not really.

Would I be better off, if I want my life to be simple, in just deciding between petrol 100% or B100 (actually, B75 is what's being supplied at this time of year). I'd still add some bio with straight D2 for lubricity.

So far, I've been very happy with my routine of filling up when I hit half empty (or half full, depending on your personality) with a 1/4 tank of bio and a 1/4 tank of petrol. I've always figured that by filling up when I hit 1/2, I'm buffering against sudden changes in fuel composition.

Why is life so complicated?

And why, when I've been on this forum for over 2 years with numerous posts, am I still labeled as a newbie? The status is based on number of posts. So you aren't a post whore....

Click to expand...

........see opinions in blue.....

CarrboroTDI said:

I can check my fuel filter for water - no problem, I'll do it - but is there anything bad about stratification other than possible gelling?

Would I be better off, if I want my life to be simple, in just deciding between petrol 100% or B100 (actually, B75 is what's being supplied at this time of year).

So far, I've been very happy with my routine of filling up when I hit half empty (or half full, depending on your personality) with a 1/4 tank of bio and a 1/4 tank of petrol. I've always figured that by filling up when I hit 1/2, I'm buffering against sudden changes in fuel composition.

Why is life so complicated?

And why, when I've been on this forum for over 2 years with numerous posts, am I still labeled as a newbie?

Click to expand...

I hope you're not adding petrol to your diesel car.

UFO said:

Drive a few miles and your tank will be completely mixed because the IP returns a significant flow back to the tank. The water thing is a different (potential) issue.

Click to expand...

Yes, but it's returned to the bottom of the tank where the fuel is also taken from. The mixing would be slow at best, particularly with a full tank.

Lug_Nut said:

The ASTM limit of water in biodiesel is 500 mg/kg (.5g/1000g, or 1:2000)
The solubility limit is about 1500 ppm (1500/1000000, or 3:2000)
Water separated out of the fuel indicates that the water content dissolved in the saturated fuel is THREE TIMES over the water limit of ASTM biodiesel.

Click to expand...

Now what's the water solubility limit of regular diesel? Once you mix in regular diesel your water solubility won't be 1500 ppm anymore, which is exactly the point I'm trying to stress. That ASTM limit for water in biodiesel seems lower than I remember. I wonder if it was updated in the last few years.

naturist said:

Of course we drive 'em. But the amount of "sloshing" around is low, unless you manage to get upside down several times. A good roll down an embankment will do the job, but just driving down the road won't. If you'd like proof of this for yourself, fill a half-liter soda bottle (glass preferred, clear, colorless, so you can SEE what happens) about 2/3 full of diesel, then add a layer of biodiesel on top. Leave some air space in it, and put it in your cup holder as you drive around. You'll find it'll just sit there on top, no matter how many weeks you drive around with it in that cup holder.

Click to expand...

I hear what you're saying, but that is not a valid test for stratification because the aspect ratio of a 500 mL bottle is about 3.5:1 L/W versus a fuel tank's aspect ratio of about 1:7.

The two aspect ratio's are about as inverse to one another as you can get. As anyone knows, tall, skinny containers promote separation/clarification while low, wide shaped containers allow for mixing from side-to-side sloshing.

I'm not saying stratification can't/won't happen. I'm just saying your experimental setup isn't context-relevant to our fuel tank's configuration and shape.

Now if you turned that 500 mL bottle on its side, transverse to the car just like the fuel tank, it would be a far closer representation. In fact, I think this is a fairly easy/excellent indicator of whether two fuels will separate, especially if you don't heat your interior.

And finally, on this point: if someone is so inclined to REALLY know if separation is happening in their fuel tank, it is quite easy to lift the rear seat, remove the fuel sender unit, and peer in there with a bright flashlight. If separation is present, you should be able to see it by gently rocking the car and looking for a wavy interfacial layer. I'd do this after driving for a bit so the experiment is relevant.


This thread seems to belong better to the AF section. Let me know your preference DA whether or not you want me to move it.

Diesel Addict said:

Now what's the water solubility limit of regular diesel? Once you mix in regular diesel your water solubility won't be 1500 ppm anymore, which is exactly the point I'm trying to stress. That ASTM limit for water in biodiesel seems lower than I remember. I wonder if it was updated in the last few years.

Click to expand...

The biodiesel will still have the same amount of water in it, and it's solubility limit is not going to change just because you diluted it with diesel.

It seems as though the issue is with adding warm biodiesel with water close to the solubility limit to cold diesel, significantly cooling the biodiesel affecting the amount of water it can retain. Then you could get some water to drop out. But for this to seem to be a serious issue, you got to have some very wet, out of spec, biodiesel. This biodiesel may not even appear clear for this to happen.

And adding biodiesel to cold diesel is probably not the best idea; if it's cold you may want to think about gelling and not add so much biodiesel.

UFO said:

The biodiesel will still have the same amount of water in it, and it's solubility limit is not going to change just because you diluted it with diesel.

Click to expand...

Once the biodiesel is mixed in, its water solubility is irrelevant. What's relevant is the water solubility of the mix which will be lower. Get it?

nicklockard said:

This thread seems to belong better to the AF section. Let me know your preference DA whether or not you want me to move it.

Click to expand...

I think the thread is fine here, but I don't have a strong preference either way. The AF forum is kind of redundant, since this is a fuels forum too. If you ask me this whole forum is way too subdivided.

Diesel Addict said:

Once the biodiesel is mixed in, its water solubility is irrelevant. What's relevant is the water solubility of the mix which will be lower. Get it?

Click to expand...

Who cares if the solubility of water in diesel is zero? If you want to make the claim the biodiesel can no longer support 500ppm water when mixed with x amount of diesel, support it.

UFO said:

Who cares if the solubility of water in diesel is zero? If you want to make the claim the biodiesel can no longer support 500ppm water when mixed with x amount of diesel, support it.

Click to expand...

You're kidding, right? That's like arguing biodiesel's gel point is unaffected by the amount of diesel mixed in. I'm not gonna waste my time having such a foolish discussion.

Bio users have almost all reported that the fuel filter will plug up due to crud that the bio dissolves from the dino-use tank. Happened to me on about the 1/3 tankful on my 240D. I've a friend with a TDI who had her fuel filter plug when she got the car and started using bio. In my case, this was the ONLY fuel filter plugging incident in almost 215k miles of driving the 240D. I always carried a spare fuel filter, but I called a tow that day because it was raining.

What I was using was only B5.

It's interesting that this is ALL the 2010 TDI manual recommends: B5, if you use bio.

nicklockard said:

I hear what you're saying, but that is not a valid test for stratification because the aspect ratio of a 500 mL bottle is about 3.5:1 L/W versus a fuel tank's aspect ratio of about 1:7.

{SNIP: large chunk of text cut for brevity}

This thread seems to belong better to the AF section. Let me know your preference DA whether or not you want me to move it.

Click to expand...

Yes, Nick, you are quite right. I think the point of this thread is not to say trouble is certain, but to suggest that there are issues here that are complex, and that COULD cause trouble under certain circumstances, and folks might be well served to do what they can to minimize their chances.

And it makes no difference to me where this thread winds up.

Folks living in the NV desert have two advantages over folks living in, say, Ohio: (1) year 'round humidity is very low, maybe 5% vs 80%, which would tend to dry out your biodiesel supply, vs. make it gain dissolved water, and (2) even on nights in the winter when it gets really cold, during the day it gets quite warm, which will help with any mixing that needs to occur.

For those who don't know how fuel distributors would mix a large supply, no, they don't shake the vat. While I have no doubt there are folks who carelessly make no effort to mix their blends, the official ways to mix such things are to either inject measured amounts into product flowing through a pipeline or to have a giant paint-paddle mixer running in the vat, or to pump stuff out the bottom and dump it back in on top for a while.

Folks mixing their own at the pump would be well served via the shaken 5-gallon jug routine, with the caveat that care be taken to mix only warm, not when either component is below 40 degrees F. Fuel pumped out of underground tanks is generally above that even in cold climates in the dead of winter, so as long as you keep your biodiesel warm, the jug method will work nicely. Certainly better than throwing cold biodiesel on top of a tankful of petro when you get back home from the station.

Diesel Addict said:

You're kidding, right? That's like arguing biodiesel's gel point is unaffected by the amount of diesel mixed in. I'm not gonna waste my time having such a foolish discussion.

Click to expand...

If it's chicken fat or pork fat biodiesel, that's a true statement. I've seen the bio gell into what looks like waxy balls within the un-gelled diesel fuel.

It's the only feedstock I've seen this happen with, however. Even when it's pure fat bio sitting in a container it looks as if it's a lot of little waxy balls instead of one big block of butter. That's been my experience with chicken fat bio.

Diesel Addict said:

You're kidding, right? That's like arguing biodiesel's gel point is unaffected by the amount of diesel mixed in. I'm not gonna waste my time having such a foolish discussion.

Click to expand...

It's not a foolish discussion. You seem to not understand the argument. You can dilute the biodiesel (and entrained water), and the solubility of the mixture goes down, but so does the amount of water. You seem to be claiming a non-linear relationship between the solubility and the amount of dilution.

Support it.

I assume that D2 doesn't solubilize as much water as bio.

I see the argument that UFO is trying to make. For the sake of argument: If you add 1 kg of B100 (saturated with water) to 1 kg of D2, there will be 1500 mg of water.(using lug_nut's calculations). Assuming that D2 holds no water, the overall mix will be able to now support 750mg of water per kg (since it is only half B100). Now there are 1500 mg of water in 2 kg of fuel. This should still be able to be dissolved by the B100.

If you are adding warm B100 (saturated) to cold dry D2, it is a different story. The situation will be the same as above, but anything that is colder cannot dissolve as much of anything in it. Since the overall mixture will be colder than the warm b100 going in, you will not be able to dissolve as much water in the mix, and water will come out of solution.

UFO said:

It's not a foolish discussion. You seem to not understand the argument. You can dilute the biodiesel (and entrained water), and the solubility of the mixture goes down, but so does the amount of water. You seem to be claiming a non-linear relationship between the solubility and the amount of dilution.

Support it.

Click to expand...

Let's say you add 1 gallon of biodiesel containing 1500 ppm of water to 9 gallons of perfectly dry/anhydrous (good luck finding that) ULSD#2 diesel.

The amount of water is constant, but the net concentration goes from 1500 to 150 ppm (I've omitted minor corrective% for differences in density to simplify calc's.) But, you now have a solution of:

1 gallon of mildly polar liquid (biodiesel)
9 gallons of non polar USLD.

Non polar hydrocarbons have less "like dissolves like" affinity for water.

Now let's say that you have a different situation:

1 gallon of biodiesel which just barely passes water content specification.

You add this into 9 gallons of USLD#2 which is also just barely passing its water content specification..

You very well may have a problem!

naturist is right: climate matters. If you're doing this in foggy, cold 1 degC Vancouver BC night, you'll probably have a gelling and/or water drop out risk.

But if you're doing the same in bone-dry Arizona you might not!


Tangent rambling: non-linear relationships of solubility occur all the time. I worked for Hewlett-Packard for a while developing Leuko dye formulations for Project: LightScribe compact discs (those discs you can burn a picture on the top face of.) One of my jobs was to set up complex solubility trials. We had 8 components composed of just 2 liquids (about 8% of total final mass) and 6 dry powders, mostly oligimers and bisphenol-A. As we added one dry component to a prior solution of the two liquids (they were hydrocarbon-like) and a powder, solubility of the FIRST powder would actually then go UP! So we'd go about doing multi-variate additions. I had to set up a very complicated 'smart' spreadsheet to successfully conduct that experiment and it took about 10 days to run all the permutations. We don't have ability to graph the relationships though--how does one produce an (n-1) multi-dimensional plot with that many degrees of freedom anyway? But it was obvious that several of the relationships were highly non-linear. Why? Cosolvency factors.

I can accept the premise of co-solvency non-linearity, but it would be nice to have some actual numbers. OTOH, water in fuel is rare, and biodiesel is usually quite dry. Low humidity, high plains desert. Having personally mixed diesel and bio in colder conditions with no issues, it's a purely academic discussion.

UFO said:

It's not a foolish discussion. You seem to not understand the argument. You can dilute the biodiesel (and entrained water), and the solubility of the mixture goes down, but so does the amount of water. You seem to be claiming a non-linear relationship between the solubility and the amount of dilution.

Support it.

Click to expand...

OK, that makes more sense and it's quite different from what you said earlier where you seemed to be saying that the water solubility is unchanged with x amount of diesel added in. I don't know if the relationship between solubility and dilution is linear. All I have in support is what the manager of Bently Biofuels in Minden, NV told me, that they got significant amount of water dropping out of solution after diluting their B100 with diesel and he warned me against doing my own blending in the tank. I don't know if they still have this problem as I haven't kept in touch and I no longer use any bio. This might be a good experiment for anyone who makes their own bio or has some B100. Add some diesel to it, mix it, let it settle, and see if you get a water layer.

Diesel Addict said:

OK, that makes more sense and it's quite different from what you said earlier where you seemed to be saying that the water solubility is unchanged with x amount of diesel added in. I don't know if the relationship between solubility and dilution is linear. All I have in support is what the manager of Bently Biofuels in Minden, NV told me, that they got significant amount of water dropping out of solution after diluting their B100 with diesel and he warned me against doing my own blending in the tank. I don't know if they still have this problem as I haven't kept in touch and I no longer use any bio. This might be a good experiment for anyone who makes their own bio or has some B100. Add some diesel to it, mix it, let it settle, and see if you get a water layer.

Click to expand...

I believe what I was saying is the solubility of the biodiesel for water isn't changed. That may or may not be the case, and your fuel distributor's "experiment" has too many variables to make the claim of reduced solubility. It's prbably a good thing you stopped using that fuel, it sounds like it was wet, not what I'd expect from Nevada fuel.

UFO said:

I can accept the premise of co-solvency non-linearity, but it would be nice to have some actual numbers. OTOH, water in fuel is rare, and biodiesel is usually quite dry. Low humidity, high plains desert. Having personally mixed diesel and bio in colder conditions with no issues, it's a purely academic discussion.

Click to expand...

I really have to beg to differ with your comment about water in fuel being rare. It isn't even remotely rare. In fact, finding diesel fuel w/o water is extremely rare. I wish we could all live in a bone-dry high desert, but we can't all fit in นเดียทศอิ. In the rest of the world's geography/climate, water in fuel is a fact of life--in both bioD and ULSD#2. During winter, if I drain my fuel filter, it nearly always has water in it. Ours are wet + cold.

nicklockard said:

I really have to beg to differ with your comment about water in fuel being rare. It isn't even remotely rare. In fact, finding diesel fuel w/o water is extremely rare. I wish we could all live in a bone-dry high desert, but we can't all fit in นเดียทศอิ. In the rest of the world's geography/climate, water in fuel is a fact of life--in both bioD and ULSD#2. During winter, if I drain my fuel filter, it nearly always has water in it. Ours are wet + cold.

Click to expand...

If you say so. Even here, until now, I've not read of very many occurrences of water in fuel and I frequent a fair number of diesel-specific sites. And of course, never in นเดียทศอิ. We just have crappy cetane numbers for D2.

UFO said:

I can accept the premise of co-solvency non-linearity, but it would be nice to have some actual numbers. OTOH, water in fuel is rare, and biodiesel is usually quite dry. Low humidity, high plains desert. Having personally mixed diesel and bio in colder conditions with no issues, it's a purely academic discussion.

Click to expand...

Yep, this is now an acedemic discussion, but still interesting. Hey, I'm splash-mixing 1 liter per 12-14 gallons, a 'splash in a bucket' (~2%) just as a lubricity additive. I always pour in the B100 before filling. Moisture? My B100 supplier (a friend) has a local lab check periodically for that and other impurities, and shows me the results whenever I want. Stratification? My clear bottle test says no, but even if I do get a little stratification, I might at times run - what - 5%, or 1%? So what.

When used as an additive in this small amount, I doubt if even the harshest climate could lead to any problems. Ijust got that bottle out of the freezer where it sat undisturbed for a few days, and it shows no signs of statification, gelling, crystalization, or anything else. It did seem a little thicker than at room temperature, but so did the Grey Goose. And the Grey Goose did have a small amount of crystalization until I drank it.

-------------
edit - God, I hope I drank out of the right bottle! I better go try it again.

Lug_Nut said:

I'd be more wary of that supply of wet biodiesel. When biodiesel is saturated enough that water precipitates out it is far beyond suitability as a fuel or as a lubricity aid.
I've been splash blending about 4 months a year for the past 8 years, just starting my 9th year. The drive home from the petrodiesel station is sufficient to mix the two. The poor analogy of a pop bottle in the cup holder does not even closely mimic the fuel tank shape. Set the pop bottle sideways, more horizontal than vertical (like the fuel tank), and you'll see how quickly the two mix.

Click to expand...

HI, Lug_Nut Where do you get your boi-diesel? I don't live far from you.

Do you think it may be a good idea to put some in my tank? Or fill up next fill up? Maybe wait until spring-time? I have a 01 NB TDI (A4 ALH) and I've never used bio-diesel before. I tried to get some in RI last year, simply because I thought it would reduce emissions and be good for the envior, but the station didn't sell to passenger cars (I was bummed out).

Where is นเดียทศอิ?

splash mixing works fine in my area

I've tried several different blends with no noticeable difference in performance, although I admit that's not necessarily a validation of my methods. I have used chicken fat biodiesel each time since it has greater BTU than soy.
I have run B100 (full tank) in 50-60 F weather with no problem (a little hard starting one morning, though).
Most of the time, I ran B67, that % only because it was easy to add 100 gallons of bio to my 150 gallon tank and then fill up to 150 with petrodiesel.
In winter months (seldom colder than 30 F where I live) I have run "winterized" B67 which consists of 100 gallons biodiesel, 15 gallons kerosene (10% of total), and roughly 35 gallons petrodiesel to fill up my 150 gal transfer tank. I "splash-blended" at the pump, and the stop-and-go on the way home was a second mix. You can feel the fuel slosh back and forth as you are towing it, so you know it is mixing it to some degree. BTW, I towed with a truck and not my car - Passat transmission NOT made for towing.
I ran biodiesel blends for about 45K miles with no incident. I am presently at 105K miles and still have not had any fuel system problems. Again, not saying my methods are foolproof, but they worked well for me in my climate (South Georgia).

Saw a link on another TDIclub thread, “Project Caddyshack” and the owner of an 82 VW 1.9 TDI Pick-up this is what the owners says he adds to the fuel tank, below:

• Currently adding ~13oz. 2-stroke oil and ~3oz. Stanadyne Performance Formula per fill-up to help with the new low-sulphur diesel fuel out there.
• Why that mix? Well, Stanadyne is formulated for the low sulphur diesel and it helps boost cetane rating and 2-stroke oil makes a low cost, low ash lubricant. Plus, it makes for easy no-measure mixing.
• My "recipe" is to take a gallon of 2-stroke oil (cheaper that way) and I pour half into an empty gallon jug. Then I pour a 1 pint bottle of Stanadyne into each 1/2 full jug. So this nets me 5 pints of mix in each jug.
• Then I simply fill a 1 pint bottle with the mix and add this all to each tank full of fuel when I fill up.
  Have also been pouring in between 1/2 and 1 gallon of straight vegetable oil (SVO) in per tank.

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