Mileage Problem

Bovie · **Posted:** Mon Nov 13, 2006 1:06 pm

I have noticed my last two tanks have taken a turn for the worst. When I bought my jeep I was getting 19mpg, which pushed it's way to 21mpg but now I'm down to 17 and 18mpg. This is horrible. It doesn't seem to matter weather I drive like a grandma or a maniac. I've got 5800 miles on it now. Do you guys think I can expect it to get better? could it be the ULSD?

alljeep · **Posted:** Mon Nov 13, 2006 1:45 pm

Bovie wrote:

I have noticed my last two tanks have taken a turn for the worst. When I bought my jeep I was getting 19mpg, which pushed it's way to 21mpg but now I'm down to 17 and 18mpg. This is horrible. It doesn't seem to matter weather I drive like a grandma or a maniac. I've got 5800 miles on it now. Do you guys think I can expect it to get better? could it be the ULSD?

Winterized Diesel.

dhubley · **Joined:** Sat Feb 18, 2006 12:00 pm **Posts:** 7

I have over 20K miles on mine, and have never seen mpg below 19.5. The winter blend does cut 2-3 mpg, but 19.5 mpg is the lowest I have seen, and I drive her hard.

I check every tank based on miles and gallons pumped. My range has been 19.5 - 28.5 driving with no mercy. Average is ~23 mpg combo city/hwy and about 21 ctiy/hwy winter blend.

AndySRT · **Posted:** Fri Nov 17, 2006 1:04 am

Ya my milage has dropped off lately from 22-25mpg to 18-20mpg. but i exspected it with the winter blend and my truck sitting for a while to keep me warm while im on my jobsite. and for those of you who say dont idle the CRD dont worry i dont i try and sustain something above 1500RPM to keep it warm.

kjfishman · **Posted:** Fri Nov 17, 2006 11:21 am

Bovie wrote:

I have noticed my last two tanks have taken a turn for the worst. When I bought my jeep I was getting 19mpg, which pushed it's way to 21mpg but now I'm down to 17 and 18mpg. This is horrible. It doesn't seem to matter weather I drive like a grandma or a maniac. I've got 5800 miles on it now. Do you guys think I can expect it to get better? could it be the ULSD?

Supposedly the ULSD has a higher cetane rating and should get better mileage but my mileage has also fallen off with the ULSD and now winter blend. You might try adding a cetane booster and next couple of tanks and see what happens. I figure it is still using less fuel than my gas KJ did.

Diesels seem to be more sensative to fuel quality than gas. Or maybe the quality of diesel is not as consistant as gas. That said try filling up at a different brand station.

Joe Romas · **Posted:** Fri Nov 17, 2006 11:32 am

[quote="kjfishmanDiesels seem to be more sensative to fuel quality than gas. Or maybe the quality of diesel is not as consistant as gas. That said try filling up at a different brand station.[/quote]

Depending where you are both gas and diesel quality vary widely :shock:

Some states monitor quality but Ohio is one that does not. If you pay for a gallon your sure to get a gallon but it maybe half water :oops:

dgeist · **Posted:** Fri Nov 17, 2006 12:00 pm

Has the weather near you changed significantly during the time that you noticed the drop? My milage dropped a few points when wintery weather hit. It's most obvoius during the week when the engine never really has a chance to warm up, but longer weekend long trips give me more normal numbers.

Might want to try plugging the block heater for an hour in the AM to "pre-warm" your engine on the next tank and see if results vary.

Dan

Bovie · **Posted:** Mon Nov 20, 2006 4:05 pm

Ya it did drop by about 10 Degree's. I guess what sucks is the fact my normal commute gives me 20-22mpg but if I do any extra city driving at all I'm down to 17-18mpg. I'm trying to be really careful and see if I can get it to go back up again.

MooseMeat · **Posted:** Mon Nov 20, 2006 7:57 pm

Why does the winter blend make such a big differance in our CRD's, my dads Ford with the big 7.? liter turbo desiel gets the same year round.

And I dont understand not being able to let the CRD idle this is new to me, most diesels do as much idleing as the do hualing.

I'm trying my first tank of ULSD as of today $2.69 for #2LSD and $2.72 for the ULSD the CRD took 19 gallons. last 2 tanks of #2 with PS aditive I averaged 21.5 mpg

Bovie · **Posted:** Mon Nov 20, 2006 8:46 pm

Well I have started to let my engine idle for at least 1 or 2 minutes to heat up just a little before taking off. I think it helps.
I'm also gonna put some Stanadyne additive in my next few tanks to see if that helps.

Gator4x · **Posted:** Mon Nov 20, 2006 9:48 pm

couple things here ya'll.

First off-Cetane is similar to octane, if you put in a higher octane than your car needs, you don't get more power out of it, and therefore do not get better mileage out of it.

Second-ULSD has a LOWER specific energy density than LSD. But only by a VERY small amount. Your fuel mileage WILL drop a couple of tenths of a point with the switch. Do not expect to get better mileage with ULSD. The only folks who will actually notice a difference are the OTR trucking companies, because they go through SO much fuel.

There's plenty of info out there on the web. Now that you're a diesel owner, get in the know!

/public service announcement

DarbyWalters · **Posted:** Mon Nov 20, 2006 11:14 pm

ULSD will have about 1% energy loss compared to LSD but that will drop mileage about 4-6% according to most sources.

Cetane and Octane rating are really kinda polar opposites if each other.

Raising the Octane level of petrol makes it more resistant to pre-ignition...so raising the Octane level makes the fuel "harder to ignite" and therefore less likely to cause detonation in higher performance engines. Raising the Octane level on "normal" engines will just waste fuel and be detrimental to mpg figures.

Raising the Cetane rating of diesel makes it "easier to ignite". Since diesels do not use a "spark" to ignite "fuel" in the cylinder, this is very important to diesels. Diesels use compression ratios of 17.5/22.5:1 to make the diesel explode. The higher the Cetane rating is on a specific fuel, the easier and more completely it will carry out this combustion process.

IMHO, since the Liberty CRD is near the lower values when it comes to compression ratio ( ~17.5:1 ), I think we can get benefits from raising our Cetane level to near 50. It will also help our EGRs stay cleaner among other things.

MooseMeat · **Posted:** Tue Nov 21, 2006 9:18 am

Gator4x I know you don’t know me but I have owned and driven Diesels for years. I'm just not up on all this LSD and ULSD fuels, and I never added an additive to my truck when I drove for Warner.

I drove OTR for Warner till I decided I wanted to be home more and not 1/2 across the country when I wanted to be hunting or with my family. The finial straw was when the dispatcher promised me I would be home for Easter and then pulled my truck out from under me the day before Good Friday I was in AZ and lived in PA, and then told I wouldn’t be getting my new truck till the following Monday and put me in a hotel for Easter weekend, I asked him if they would fly me home since they promised me I would be there he told me no way and my first load was going taking me to California, I already had my stuff so I shipped it all home and jumped on a plane and that was that.

I have noticed that it did seam to start a lot quicker this morning with the ULSD, and thanks for all the info.

no-blue-screen · **Posted:** Tue Nov 21, 2006 10:40 am

Hexadecane (also called cetane) is an alkane hydrocarbon with the chemical formula CH3(CH2)14CH3. Hexadecane consists of a chain of 16 carbon atoms, with three hydrogen atoms bonded to the two end carbon atoms, and two hydrogens bonded to each of the 14 other carbon atoms.

Cetane is often used as a short-hand for cetane number, a measure of the combustibility of diesel fuel. Cetane ignites very easily under compression; for this reason, it is assigned a cetane number of 100, and serves as a reference for other fuel mixtures.

---

Octane is an alkane with the chemical formula C8H18. It has 18 isomers.

One of the isomers, 2,2,4-trimethylpentane or isooctane, is of major importance, as it has been selected as the 100 point on the octane rating scale, with n-heptane as the zero point. Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance. It is an important constituent of gasoline.

KenJennings · **Posted:** Tue Nov 21, 2006 10:40 am

This is really strange, because my current tank -- about 10 days from purchase -- is getting better mpg than I've had for routine driving in the past six months.

Ordinarily the fuel light comes on between 390 and 400 miles which works out to barely 20mpg when calculated at fillup.

It is already at 415 miles on the trip OD and still has a quarter tank on the gauge. Weird. Makes me think there are diesel fairies that come by at night and put in more fuel. It might be getting over 22mpg on this tank, perhaps even 23. A very big deal -- it hasn't done this good for my daily drive since April.

Edit on 2006-11-24: Just crossed the 10,000 mile mark a couple days ago. Finally fueled up today. The most recent tank discussed above did actually turn in 23.7 MPG for strictly routine driving between work and home.

The CRD has been turning in 20 to 21 MPG consistently for at least the last three months. It only did better than 22.6 MPG during extended highway driving on vacation. So, there definitely must be diesel fairies adding fuel at night. I should stop spraying for bugs around the house, just in case.

Jeger · **Posted:** Tue Nov 21, 2006 10:51 am

KenJennings wrote:

This is really strange, because my current tank -- about 10 days from purchase -- is getting better mpg than I've had for routine driving in the past six months.

Ordinarily the fuel light comes on between 390 and 400 miles which works out to barely 20mpg when calculated at fillup.

It is already at 415 miles on the trip OD and still has a quarter tank on the gauge. Weird. Makes me think there are diesel fairies that come by at night and put in more fuel. It might be getting over 22mpg on this tank, perhaps even 23. A very big deal -- it hasn't done this good for my daily drive since April.

Ours has been getting a little better as well, could it just be breaking in at 15700 miles? I did change the oil quite frequently when it was new.

Mileage Problem

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