Fuel milage drop

[Clay]

I recently noticed a huge drop in fuel mileage and thought something was wrong with the truck. Well since then i have experimented with mileage on diesel vs WVO. And what i found was i am getting the same good mileage i was before when burning diesel (21-22) but when i switch over to vegi I am lucky to get 17.
Now when i noticed this (I monitor mileage pretty often) i had just done and oil change and pumped a new batch of WVO in the tank.
So its it possible there was something about this oil that it has a really low cetane value or something? I might add one place i get oil from has a REALLY high % of animal fat in it these days. They use there oil alot longer since virgin oil has gone up so much and in doing this, the oil looks really dark and half the cubie is cloudy animal (chicken to be exact) fat. Would this be reason to notice lower fuel mileage?

[Marv]

So you're experiencing the same thing Clay?

I have noticed a significant drop as well. Mine truck never has been stellar in the mileage department, but still did better than it's doing now.

When I bought it, it was 19-21 on the hwy. Added oversize tires (325/65/18 - without corrected speedo) and it went more toward 16-18 (sometimes would do 19). Threw the V3 on there and it's dropped down more to 14-16 (again, sometimes it will get 16+).

Been doing more city driving than usual and it's down around 13.5 - which sucks. I've been pondering on this for a while now trying to think of causes for the decrease.

I know the tires are hosing up the mileage indicator and the fact that 500+ pounds of additional fuel in the rear doesn't help, but there obviously has to be something else going on.

Like Clay, I too have wondered about the cetane value of the vegi oil in comparison to diesel. I have read that oil has slightly less energy compared to straight #2. Whether or not this is the gospel, I'm unsure.

I know I was hoping for around 800-850 miles on one, 60 gallon tank of vegi. The results have been more like 650-700 when I'm stretching it.

By the way, how are you guys hand calculating your mileage on vegi? Do you have flow meters on your filtering setups to record how much vegi is pumped into your truck tanks? I've been tracking it via the meter in the dash, but would like some hard numbers to compare it too. I can only assume the factory meter is fairly accurate - if I had to guess it measures fuel consumption based on the injector pulse width. If it records that and does a bit of math, it's not hard to determine a MPG rating.

It's got me a bit stumped to be honest...

Thanks!

[Clay]

I have only seen this kind of drop in the last 400 miles ...out of my 55,000 miles on vegi. So thats why thins is particularly confusing to me. I would think if there is some sort of variable that would cause a milage issue like this, i might have seen it before now but i have not.
i use the dash computer and i know it reads about 1 mpg high but if it shows a drop of 4-5 mpg, there is indeed a drop. So if i am reading 22, then i know its really about 21 and when it reads 17....16 is the real number. There is no real way i can see to hand calculate when your starting on one tank and switching to another and vice versa without getting into some money on system mods and I am not that interested in the actualy numbers when i know the amoutn of error in the dash computer.

[Jack_Toepfer]

I noticed a loss of power as well as a loss of MPG on my first tank.

The fuel gauge on these tanks are impossible to trust. The only way to determine your mpg on oil that I have thought of is by measuring how much you're putting in your tank. I tried to fill mine as far as possible so it would be easier to re-fill to the same spot. Then reset your trip odo when the light goes on. When you park the truck track how many miles you put on that trip. Wash, rinse, repeat. This way you're only monitoring your veggie use and not #2 and idle times. I'm still experimenting with my fill station so I don't have a good way to measure how much is going in my tank.

The way I look at it...

Spending $3200 on the kit and losing 2-3 mpg but still driving for free still outweighs buying a Civic and getting 30mpg.

[Marv]

Well, I reset mine last night on the way home and it averaged about 16-16.5 over the 40 miles I checked it. For my truck, that's probably not too bad given the oversize tires. This was with the cruise set on 70 the whole time.

Last time we went on vacation I was on diesel. The highway numbers from yesterday match up pretty well with what I was getting on diesel earlier in the year, so I guess that's a bit reassuring.

Overall though, I still think I've lost a bit of both MPGs and power as Jack mentioned.

Two things I think can majorly affect the mileage on these trucks is aero and tire inflation. Since they're basically ~4 ton bricks going down the road, the difference in MPG between 60 and 70MPH is pretty substantial. Anything over 70 I would think would have an even greater effect.

What speeds are you guys averaging when you check your mileage? Have you varied it any to see if the results change?

Also, given the weight (and the fact that many run oversized tires), I'd bet the additional resistance encountered from running a lower pressure is greater than your normal car with a low, factory size tire. Right now, my 325/65/18 ProComp Xtreme ATs are set at 55psi front and rear. This was primarily to ensure they wore well (and they are), but I'm thinking of sacrificing a little wear for a while and see how much 5-10 psi will affect my mileage.

I don't know if any of you guys are running those tires, but they are heavy...and wide. I always dread rotating them...haha.

I'm not regretting my choice to go to vegi - as Jack said, I'm still running free fuel. But, at the same time, I'd still like to get better mileage too.

[Clay]

i check milage at 65 mph usually.
The wierd thing about this is i hooked up the 5er last weekend and i was getting above normal milage towing. Before this milage drop, i could tow the camper and get 11 mpg...last weekend i was showing 12.5 while burning vegi.
I think its the animal fat content here, that is the only variable that has changed about my oil. Lots of animal fat in it...so chicken juice has a lower cetane level than the soybean oil?

[Marv]

i check milage at 65 mph usually.
The wierd thing about this is i hooked up the 5er last weekend and i was getting above normal milage towing. Before this milage drop, i could tow the camper and get 11 mpg...last weekend i was showing 12.5 while burning vegi.
I think its the animal fat content here, that is the only variable that has changed about my oil. Lots of animal fat in it...so chicken juice has a lower cetane level than the soybean oil?

It's not uncommon for me to get 10-12 towing a gooseneck - ~15K pounds.

Do you use any cetane boosters in your vegi oil?

[Marv]

Here's some interesting info:

(Sorry about the spacing...for some reason it doesn't appear right.)

Comparison of properties of diesel, canola oil and commercial US biodiesel
Diesel Canola Oil Biodiesel
Density kgL-1 @ 15.5 deg C 0.84 0.92 0.88
Calorific value MJL-1 38.3 36.9 33-40
Viscosity mm2s-1 @ 20 deg C 4-5 70 4-6
Viscosity mm2s-1 @ 40 deg C 4-5 37 4-6
Viscosity mm2s-1 @ 70 deg C - 10 -
Cetane number 45 40-50 45-65


Found it here:

http://journeytoforever.org/biodiesel_yield2.html

[Marv]

Here's another article with some discussion on cetane values:

http://blog.vegetableoilroadtrip.com...vegetable.html

[Jack_Toepfer]

As you can see in my sig, I'm running 40" tall tires that are 15" wide... not really the best combo for MPG. BUT I was still getting 15mpg.

I can't avg a mph for my mpg... but I do a lot of mixed driving. I race, I tow, I speed.... I slow. (ok, enough)

On the thruway I don't necessarily follow the posted limits... and it requires a lot more power to speed than it does to cruise with traffic.

[greasyX]

I check mpg at 62.5(100KPH),when Iadd cetene boost(gray Powerservice) to my WVO i get 1.3 MPG better,hand calculated.I also add Injector cleaner(Lucas in the clear container),I try to use the same products that saved me money in the big Rigs,in 500,000 miles power service,and Lucas never let me down.For the guys worried about H2O in the WVO I suggest Stanadyne Fuel treatment,summer and Winter blends this is used to prevent condensation in 18 Wheeler fuel tanks,due to Regional fuel differences,as well as Geographical Tempature changes(Like driving From NH in Feb.(-15F) to FLA(80F).I Am firm believer in these additives.For fun check ASTM on Lucas,Some of Them have Virgin Veggie oil in it!!!.I guess they know how good the stuff is for lubrication.........grease out

[Marv]

As you can see in my sig, I'm running 40" tall tires that are 15" wide... not really the best combo for MPG. BUT I was still getting 15mpg.

I can't avg a mph for my mpg... but I do a lot of mixed driving. I race, I tow, I speed.... I slow. (ok, enough)

On the thruway I don't necessarily follow the posted limits... and it requires a lot more power to speed than it does to cruise with traffic.

Ah, I didn't notice that...man, those have to be worse than mine. 15 MPG isn't bad for that combo really.

[Marv]

I check mpg at 62.5(100KPH),when Iadd cetene boost(gray Powerservice) to my WVO i get 1.3 MPG better,hand calculated.I also add Injector cleaner(Lucas in the clear container),I try to use the same products that saved me money in the big Rigs,in 500,000 miles power service,and Lucas never let me down.For the guys worried about H2O in the WVO I suggest Stanadyne Fuel treatment,summer and Winter blends this is used to prevent condensation in 18 Wheeler fuel tanks,due to Regional fuel differences,as well as Geographical Tempature changes(Like driving From NH in Feb.(-15F) to FLA(80F).I Am firm believer in these additives.For fun check ASTM on Lucas,Some of Them have Virgin Veggie oil in it!!!.I guess they know how good the stuff is for lubrication.........grease out

Greasy, any particular place you purchase the Lucas and Stanadyne or should any major auto parts chain carry them?

So do you add all three with each tank of WVO?

[powerstroke73L]

I add Power Service (white bottle) to each tank of WVO as well as the diesel tank. Not really sure how much it's helping the WVO, but I figure it can't hurt. I've always used Power Service when running on diesel and definitely noticed more power, better mileage, and smoother running.

[Jack_Toepfer]

I'm going to throw the rest of the lucas I have sitting behind the seat in my wvo tank. I haven't had to put anything in the diesel tank for a while... ANYTHING