B20 fuel economy vs ULSD - PeachParts Mercedes-Benz Forum

clydecpa · #1 10-05-2006, 11:33 AM

After several fillups with ULSD have consistently gotten me an average of 28.5 mpg in mixed driving (60/40 city/hwy) I decided to try a tank of B20 (soy here in middle TN). I figured with the added lubricity of B20, the negligible drop in fuel economy would be offset by me not having to use a can of one-shot lubricity formula Stanadyne.

Well, a slightly bigger than expected drop off in fuel economy resulted. I got 26 mpg on the B20 tank, same driving, same a/c usage (if not less). At current fuel prices that means about $4.58 more in fuel cost to run B20 in my 1996 E300D. Back off the cost of not using the one-shot ($2.50 per bottle if you buy by the case) and you are only talking about $2 per tank more cost to use B20. I have already run another tank of 100% ULSD and gone right back to 28.5 mpg.

I hate to be the typical US consumer, but there is something psychological to me that I like about going 500+ miles before I have to fill up running 100% ULSD. I don't mind using the additive either; heck, a case of it lasts 12,000 miles or so. Also, I did perceive a very slight reduction in power when attempting to accelerate with the B20.

I work for a Caterpillar dealership and recently read Cat's statement on using Bio-fuels in Cat engines. They claim something like an 8-10% (if I am recalling correctly) reduction in fuel economy for B100 due to lower BTU's. However, that is based on a Biodiesel from some other plant than soy, which we have in these parts. Soy would have even lower BTU's and more disparity. I was really surprised I got this difference since I had run B20 some in my previous Passat TDI and only observed a 1 mpg drop off. There are other variables I am sure. Two completely different cars, plus one a turbo, the other not.

For my experience, I think I will stick with 100% ULSD plus the lubricity additive for a while. I'd sure like to run a higher BTU bio-d to see if it would make some difference. YMMV.

Jadavis · #2 10-06-2006, 02:03 AM

The VW TDI's come with dished piston tops. It was an improvement pioneered by Elsbett years ago. VW took the idea and put it into their production vehicles. For some reason it helps you get a more complete burn out of biofuels.

http://www.elsbett.com/us/about-us/introduction.html

-Jim

greasybenz · #3 10-06-2006, 02:48 AM

one tank isnt enough to determine that you really got the drop in mileage. You need to run more then one tank of B20 to know for sure there werent other variables in your driving that caused you to get lower MPG.

Try 2-3 more tanks of B20 and report back. B20 doesnt seem to drop the MPG in the passat and its pure highway driven back and fourth. B100 drops 5mpgs, 38mpg is average on B100 With B20 or lower we get 40-42 which is the same for ULSD with some diesel kleen or half gallon of bio.

#4 10-06-2006, 11:52 PM

Running B20 over 4 tanks, I got between 21 and 23mpg. I filled with regular petrodiesel two weeks ago and went up to 26.53mpg today.

aklim · #5 10-07-2006, 02:43 AM

Didn't notice much with B20. B40 and I lost a little mileage.

I do a splash mix because I want to keep the fuel consistant. B20 is 20% Biodiesel and 80% D2. If I accept B20 from the pump, I cannot be sure of the 80% D2 and it's quality. I dump a measured quantity of B100 into a tank with a known amount of D2 and from the same station to keep the quality of D2 consistant.

retmil46 · #6 10-07-2006, 02:45 AM

I've had the opposite experience in this area. With both the CRD and 300D, actually got better MPg with B20 than #2 dino. Think there's two reasons for that - ULSD still hasn't really kicked in around here, and the #2 dino available is of such low quality to begin with that the cetane boost from the bio actually helps matters. I know both vehicles run much smoother on B20.

aklim · #7 10-07-2006, 02:56 AM

I ran B20 from the pump and it didn't differ from D2 at all. When you got better mileage, did you use B20 from the pump or mix it? Reason I ask is because there is a chain that sells crappy D2 that gives you less mileage. So, if you got bad D2 your mileage goes down and B20 has a very strong component that can screw the mileage up. The D2 could be better or worse.

retmil46 · #8 10-07-2006, 11:02 AM

B20 I use is straight from the pump. The place I mentioned is a full-fledged truck stop, 20 pumps in the truck area with half of them #2 and the other half B20, one set of B20 pumps actually have the smaller "automotive" size fill nozzles. They used to be branded as Chevron, but sometime in the past few months switched over to Crown. Huge above-ground storage tank, a plus in my book, as nearly all of the service stations in this area are old and have underground tanks.

Unfortunately, the one Citgo station where I got the present tank of #2 is one of the few small local stations that does have an above-ground tank and a small truck area (6 pumps), has a good turnover rate on their fuel (plenty of business).

Oops, posted the location on a different thread. Place I buy B20 is Homers Truck Stop, Stameys Farm Road exit on I-40 in Statesville NC, 6 to 8 miles west of the I-77 interchange.

aklim · #9 10-07-2006, 11:14 AM

Quote:

Originally Posted by retmil46

B20 I use is straight from the pump. The place I mentioned is a full-fledged truck stop, 20 pumps in the truck area with half of them #2 and the other half B20, one set of B20 pumps actually have the smaller "automotive" size fill nozzles. They used to be branded as Chevron, but sometime in the past few months switched over to Crown. Huge above-ground storage tank, a plus in my book, as nearly all of the service stations in this area are old and have underground tanks.

Unfortunately, the one Citgo station where I got the present tank of #2 is one of the few small local stations that does have an above-ground tank and a small truck area (6 pumps), has a good turnover rate on their fuel (plenty of business).

The question that is difficult to determine is whether the biodiesel I had is bad or what. However, I have had diesel where I fill up and instantly lose power and mileage. Normally you go 600 miles on a tank and you now go 550 max. Switch back to your usual source and you get 600 plus. With that in mind, the way I do it keeps the D2 constant. I wish the stations would offer biodiesel in a mix form. B100 in one tank and D2 in another. Select mix and it gives it to you.

retmil46 · #10 10-07-2006, 11:18 AM

On a trip to Texas last December in the Jeep CRD, you could definitely tell the difference in fuel quality. Tank of B20 from Homers gave me better than 30 mpg (beast is only rated for 26 highway). Tank of chevron in Nashville and a tank of Exxon from Little Rock dropped down into the low 20's. Tank of Diamond Shamrock from east of Dallas soared back to over 30 mpg.

On the return trip, stopped 30 miles west of Texarkana and topped off with Diamond Shamrock. That tank got me all the way to the east side of Nashville, 520 miles on 17 gallons. Not bad considering that beast is 1000 lbs heavier than the 300D and has the aerodynamics of a brick.