Deisel/Flexfuel/Gas for tow vehicle

[Al-n-Sue]

Chrysler has a similar vehicle - a hybrid Dodge Durango coming out for 2009. The system was jointly developed by GM and Daimler/Chrysler. The Durango (and upscale sibling Chrysler Aspen) will use the MDS HEMI engine - so you get electric to get you going and move you around town, a 5.7 HEMI to tow with (I think I saw a tow rating of about 7500 lbs) and the MDS engine to give some non-towing highway economy.
And all with a nice (i.e. BIG) pricetag.

 

[Joseph]

Thanks Al and Sue . . .

I was thinking about the Durango as a possible multi-use vehicle. Towing and everyday duty… For now, I do not have to cross that bridge yet. Amen! The company I work for buys us Dodge Caravans to drive and I have been impressed with how well they hold up. We do not baby them... Wonder how big the price tags are going to be on these machines!

 

[ng2951]

Electric has many of the advantages of diesel. Electric motors are torquey little things.

I am not sure how the battery systems are maintained. I am guessing that hybrids aren't as reliant on batteries as pure electric cars are.

 

[Mr. Adventure]

Hybrids use electric motors to boost a bit when you accelerate and they use the electric motor as a generator to put juice back into the batteries as you brake. The idea is to recapture energy that would otherwise be wasted.

The batteries typically don't hold a lot of juice, just enough to help your gas mileage.

 

[ng2951]

...The batteries typically don't hold a lot of juice, just enough to help your gas mileage...

What I don't know is how many batteries they do use. If you are using lead-acid batts, 3 years is about the typical life in deep south. If they are using a different technology, then life could be much longer.

Either way, if it uses a handful of batts, that might not be too bad when it comes time to change them out. If it uses a bucket load, that might be like buying another engine or two...

 

[murphyb74]

>>Seems there is a Hybrid Tahoe already out

I read a review of the Tahoe hybrid - they had a lot of good things to say about it, including that it does in fact give you 20 mpg or better with city driving. The downside they mentioned is that the regular gas Tahoe starts at $35,530 while the Hybrid Tahoe starts at $50,490!!

As for flex-fuel, My Chevy Suburban is flex-fuel (can run up to E-85). Below is a link to an Edmunds.com test of E-85 vs gas where they found E-85 gave you 20% - 25% less mpg. The owners manual for my Suburban states that towing is not recommended while using E-85.

http://www.edmunds.com/advice/alternativefuels/articles/120863/article.html

 

[Mr. Adventure]

What I don't know is how many batteries they do use. If you are using lead-acid batts, 3 years is about the typical life in deep south. If they are using a different technology, then life could be much longer.

Either way, if it uses a handful of batts, that might not be too bad when it comes time to change them out. If it uses a bucket load, that might be like buying another engine or two...

Here's a lot of real world experience:
http://greenhybrid.com/compare/mileage/

 

[rickst29]

most current models DON'T use lead-acid.

If they are using a different technology, then life could be much longer....

The battery packs in MOST hybrid cars, e.g., Toyota, Honda, non-plug in Ford Escape, are currently Ni-MH, the same 1.3V (nominal) cells as you use at home. The "Gen-2" Prius had 228 of these cells in Series, arranged in 38 modules of 6 cells each. This offered a nominal maximum voltage of about 275 volts. The current "Gen-3" Prius actually has fewer batteries, using just 28 modules. Same modules, nominal voltage is therefore reduced to about 200 volts. But, the new Toyota systems add a fancy inverter which raises the working voltage to 500v, while the old ones (Gen-1 and Gen-2) just used the battery output voltage unchanged.

Because Ni-MH batteries don't like being drained to a low state of charge, Toyota only runs them down to about minimum level of about 50% charge. This is one area where future "plug-in" hybrids could be made differently-- using either deep-cycle lead-acid types (including Gel cells) which are cheap and reliable but but very heavy for the amount of energy which can be stored and actually used; or lithium-ion, which are expensive but better than NiMH in nearly all other characteristics (max number of charge cycles, energy density, etc.) The big problem with Li-ion right now is, they just wear down over time, typical life expectancy is only 3-4 years.

Nearly ALL technologies are under continuing development: li-ion "thin film", lead acid batteries built with carbon foam, li-ion with silicon nanowires, and etc. Also, lots of research is going into energy storage via flywheels, rather than batteries. The technology is still developing quickly, and some of the aftermarket plug-into-the-wall conversion kits which are already available replace the original battery packs with li-ion as part of their kits.

 

[Dixielou]

Al-n-Sue, you can find a most up-to-date article that addresses your original question "Diesel/Flexfuel/Gas..." in the current issue of Motor Trend magazine (July issue page 74). The article is titled "diesel revolution", but after reading this technical and well researched discussion on the subject, it is clear to me that the "diesel revolution" may not be that great a revolution after all--at least not for those of us who tow lighter RV's.

 

[rickst29]

semi-OT: Breakthrough in Li-Ion technology?

The big problem with Li-ion right now is, they just wear down over time, typical life expectancy is only 3-4 years.

I just saw, on a India-oriented computer/telephony site, that "Hitachi Maxell and a number of universities and firms in Japan have created a design for a Lithium Ion battery that will last 20 times longer than current units." Cheaper, too, replacing the expensive Cobalt with a bunch of nano-manganese something-or-other. Unfortunately, though, actual production is estimated to be at least 4 years away. Full post here: http://www.itexaminer.com/PCs/tabid...um-Ion-batteries-to-last-20-times-longer.aspx

 

[Mr. Adventure]

The big problem with Li-ion right now is, they just wear down over time, typical life expectancy is only 3-4 years.

I've wondered about this for years, since we haven't had such great experience in our flashlights, phones, and shavers with rechargable batteries. But we also know that they last a lot better if you don't overcharge them or run them all the way down.

Most important, Toyota says their battery life expectancy is 150,000 miles. On GreenHybrid.com it's east to find people talking about potential battery replacement issues, but it's hard to find anybody who's actually had to replace any, and there is now a fair amount of 100,000+ mile experience talking on that site.

For a tow vehicle, however, I think I'd stick with the standard TV versus the hybrid. The continuously variable transmissions are designed for people with smooth and easy acceleration, and they really haven't been tested yet under heavy duty conditions.

 

[Al-n-Sue]

MPG comparison for gas and diesel

One vehicle I'm considering is a Jeep Grand Cherokee with the CRD diesel option - it is supposed to be certified for all 50 states in 2009 and has a towing capacity of about 7500 lbs.

I found a web site with EPA mileage numbers - www.fueleconomy.gov. I used their numbers for mpg for a 2008 Jeep Grand Cherokee with the 4.7 L V8 and the 3.0 L diesel V6. (gas 14/19, diesel 17/22). Using an average of 18000 miles a year and 60%/40% city/hwy driving, and the current local prices of gas and diesel (3.89 and 4.79), I figured that it costs $135 MORE per year to run the diesel! In addition, when I increased the miles driven per year, the cost difference was greater! The more you drive the more it costs!

So unless the price of diesel comes down, or I find myself driving more hwy miles than city, the diesel doesn't look like a good choice. Of course, if this were a pickup, the results could be different. Lots of factors to look at. The only good thing I can see about the diesel version now is the low end torque - makes towing so much easier.

Food for thought.
Alan

 

[tucsoncarol]

The reason I will go diesel with my next tow vehicle is the number of people I personally know who have diesel trucks with over 2 and 3 hundred thousand miles on them. I keep my vehicles 'til they die anyway (currently '93 Dakota and '00 Yukon XL) and that sort of engine life may make my next tow vehicle my last. I have great hopes for the new iteration of diesels due out starting '09.

 

[larsdennert]

Wow that's really poor mileage for a diesel. That is disheartening. My V6 4Runner in stock trim would match the diesel. Also tows the TM but probably not as well. The Toyota gas motor will probably go longer than a Jeep Diesel IMO. I have lots of friends with 20 years old toyotas with many hundreds of thousands of miles.

 

[allenj]

The EPA changed their formula for calculating mpg in the 2008 model year, and apparently really shortchanged the diesels (hybrids took a hit as well). Many diesel owners in the forums I've read report real world mpg figures about 15%+ better than the new EPA numbers. As always, your mileage may vary

 

[Al-n-Sue]

Updated formula

Based on the comment about faulty EPA figures, I bumped the mpg for the diesel by 2 mpg and corrected the diesel price ($4.69 instead of $4.79) and I get about a $450 savings per year using diesel.

With the predicted longevity of the diesel that makes it a good option.
Alan

 

[ragmopp]

With the predicted longevity of the diesel that makes it a good option


MAYBE. And that is a big maybe to me. I would tend to believe the EPA to my friends telling me how good their mileage is with their diesel. As everyone expects a diesel to get real good mileage, to tell someone that they made a mistake with their diesel and got mediocre mileage (and paying the very high tariff for the diesel engine) would lead for some unscrupulous people to fudge a higher mpg.
As to longevity, as Larsdennert pointed out,regular gas Toyotas are noted to get two to three hundred thousand miles routinely. How do we know that these 'new' diesels will, in reality, get that long of a lifespan?

Until one of the members here actually gets one of these new breed of diesels and reports significantly higher mpg, I will be extremely skeptical. I do believe that nobody here would fudge there mpg, just to prove a point.

Mike

 

[Mr. Adventure]

Most people don't exercise enough care in figuring their mileage. I've even had mechanics tell me that they were getting ridiculously high silly mpg numbers. The only measure that counts, of course, is a log book with the miles driven and the gallons purchased so that you're using real miles and gallons. For planning purposes, I discount a little from the EPA numbers, and hope to find a little upside in the real numbers. The good news is that they should provide a common standard for comparing vehicles before purchase.

That being said, the new EPA numbers are supposed to be more accurate under real world conditions, but I've been wondering when/how they are going to adjust those for the reductions caused by adding alcohol to the mix (10% alcohol x 40% loss in heat content vs gasoline is a 4% loss in fuel economy).

 

[allenj]

http://www.epa.gov/fueleconomy/420r06017.pdf

This is the official document describing the new fuel economy standards. On page 8 there is a chart comparing reported mpg values from users to the official calculated numbers (the 'YourMPG' program'). The following statement appears below the chart - note the final quoted sentence.

"As can be seen, diesels appear to perform the best with respect to their label fuel economy, outperforming the label by 4.3%. Conventional gasoline vehicles come very close to meeting their label, falling short by only 1.4%. Conventional vehicles with relatively high combined fuel economy (here assumed to be 32 mpg or more, representing the top 10% of conventional vehicles in terms of fuel economy) performed only slightly worse, falling short by 1.7%. Hybrids fall short by a much larger margin, 8.2%. Thus, the greater shortfall seen with hybrids appears to be more related to hybrid technology than to simply high levels of fuel economy.

With respect to the mpg-based label values, diesels still perform the best of the four types of vehicles, now exceeding their label values by 18%."

While I admit to not having personally digested the entire 179 page report, I have gleaned enough info to see that the EPA tried to adjust for such factors as larger amounts of stop and go driving and ethanol content in gasoline, neither of which improves the estimate for a diesel driving on the highway towing a camping trailer

With all that said, I'm personally getting to the point where I think the cost-benefit analysis is close to break even between gas and diesel for equivalent vehicles due to the difference in fuel cost. I still prefer diesel for towing torque when pulling the camper and good highway mpg, but if other factors are more important to you don't worry too much about the cost difference.

 

[Mr. Adventure]

EPA Fuel Economy

Thanks for the link to the 2006 EPA report recommending the new standards. I spent a few minutes studying up, and best I can tell, they are still having a lot of difficulty comparing different years and different fuels:

http://www.epa.gov/otaq/cert/mpg/fetrends/420s07001.htm

I read their section that talks about their data and assumptions, but I'm still wondering if they mean gasoline when they say gasoline, instead of the 90% gas/10% ethanol we're buying at the pump. Perhaps someone with more time and patience than me can figure this out for us.