Former VWDieselParts.com Forum

I just started running my 1990 Jetta on homebrewed biodiesel. Right now I am running about B-50. What kind of mpg can I expect using bio? Everything I have read on other biodiesel boards suggests that the mpg stays the same. I had not even thought about this as I was more occupied with the production process. Thanks for this board. By the way this is my first diesel and my first VW. It has been a lot of fun so far.

Good question but I don't know the answer. I want to say I'm starting to do the same as you. Will start building the processor soon. I bought a water heater and next to buy is the big pump. BTW, I'm in Michigan too, west side.

should bet the same milelage in the rabbits and maybe better because it will lubricate you injection pump better and take less power to drive your injection pump, plus allow your timing advance piston to move easier thus improving your pump timing through the rpm range

hope this helps

later
Justin

Expect less mpg because Biodiesel has less btu's than dino diesel , however the octane is higher. However, the difference may not be noticeable.
Watch for your filters to get plugged, but expect your engine to run quieter. I thought something was wrong with my Cummins at first because when I'd accelerate on the highway it didn't make a bunch of noise.

Good Luck,
Max

When running high percentages of biodiesel you may also notice that you exhaust has more of a blue tint to it.

In my thesis testing Biodiesel blends made as much hp and torque as diesel if not more power and had better torque curves, the only time that biodiesel did not make more peak power than diesel was with B100 but it was only like 3 percent, but the new ULSD has a lower BTU rating than the stuff that I tested with

the most interesting thing that we saw in testing was the fuel temp coming out of the pump when using biodiesel was around 20 or so degrees F cooler which is why I said that you should see an increase due to less friction on the pump

hope this helps

later
Justin

we use to use biodiesel in our landscaping trucks. We used a mix of 30% diesel to 70% biodiesel. It did lower the mpg about 10%-15%. also for some reason it made the engine seem alittle more lively and alittle better throttle response. (not exactly sure why)... But who really cares for 35-45cents a gallon to make biodiesel if i got 50% of the original mpg i'd still be happy

In my folks' Passat TDI we notice a decrease of about 3 mpg running B100 versus running straight diesel. But that car was designed to run on modern ultra-low-sulfur diesel fuel that has no lubrication and as such the main injection parts are lubed by engine oil instead. So the only effect of the bio is to decrease volume energy content of the injected fuel, meaning lower mileage. But in my Rabbit, the increased lubricity of the biodiesel makes a big difference in how easily the engine runs because it makes the pump a lot easier to turn. So in that car I notice a lot more power and response and smoother running on B100 and absolutely no change in MPG. I guess the increased lubricity just about balances out the decreased volume energy content.

So the answer is not that simple, it depends on the engine. But for an older rotary-pump IDI VW diesel, I think you should expect not that much deviation, just a much nicer running engine and more power with about the same mileage.

I made my first batch a few weeks ago, and have noticed a 3 - 4% decrease in mileage. This seems consistant with another one or two posts here.
My engine was rebuilt 6K miles ago, and I also had my fuel pump and injectors professionally rebuilt (not just resealed). I think with the rebuild the components are changed to be insensitive to the lower sulfer fuels, so there would be (again echoing another post) no gain from lubricity, merely less BTU's per cc of bioD.

My costs for manufacturing are now down to around .70 per gallon, so I'm quite happy reducing my rabbit NA from 44 to 40 MPG.

Please bear in mind that I have no accurate method of measuring the gallons into the car at this point, so my calculations are based merely on rough estimates and the ol' "lookslike' method.

Some of the initial loss of fuel economy can be due to the fuel filter clogging due to the cleaning effect bioD has on fuel tank, especially older cars. Have extra fuel filters on hand and slowly increase the amount BioD concentration...5,10, 20, etc. Be prepared to stop and swap it out, or better yet, change more frequently. Eventually you will have a clean and lubricated fuel system. The same applies to using biodiesel for home heating.

OK, so I am running my first tank of B20 in my 81 rabbit. I will be interested to see how it goes, and if I notice a difference...of course, it may be a while, I only fuel up once a month!

Gotta love that...
I've been getting between 44 and 49 mpg so far with dino diesel...interestingly enough, I actually seem to get better mileage driving around town than on the highway...

jettaveg wrote:I just started running my 1990 Jetta on homebrewed biodiesel. Right now I am running about B-50. What kind of mpg can I expect using bio? Everything I have read on other biodiesel boards suggests that the mpg stays the same. I had not even thought about this as I was more occupied with the production process. Thanks for this board. By the way this is my first diesel and my first VW. It has been a lot of fun so far.

Our 2007 VW Caddy 1.9 L TDI with DSG gives the same mileage on Biodiesel as it does on Diesel.
The only difference is the engine is less noisy and has "smoother" acceleration.