Fuel economy/durability cost-benefit analysis

[JSteward]

Hi guys, this is the first time I've posted in this section although I've been posting in the 6.5L for awhile.
REASON FOR MY ARIVIAL:
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=26390

Basicly, I haven't heard good things about my 6.5L. I love my truck and was glad I wasn't having any of the problems others were having. But I felt in the back of my mind (based on others' experiences) that I was driving on top of a time bomb... and last week it happened. Slung a rod. Engine DEAD.

I could rebuild w/ another 6.5L. But I just don't trust the motor... Truck is in perfect shape, but I'm nervous about pumping $4-5000 dollars into the engine.

I gave $9000 for this truck. It had 125,000 miles on it. A DMAX would cost at least double that price. Are they really that much more durable. I'll likely never trade the truck in. I want something that I can put some miles into.

So, if someone gave you $25,000 to invest in a work truck, would you buy a DMAX or would you buy TWO 6.5L trucks (drive one till it breaks down, then buy another).

What would make the DMAX a better buy?

I'd prefer a crew cab, long bed, dually. Will the DMAX get considerably better fuel economy? I think I've read the LBZ gets better economy than the LBY.... right?
If I go w/ DMAX, are there year models that are better than others... I mean, is there significant upgrades in terms of durability, fuel economy, etc with an '06 rather than an '04.

I'm sorry for all the questions, but my butt is in a jam and I'd like to hear any comments from as many people as possible to help me feel comfortable about any decisions I'm about to have to make... My family is center in my life and considering I'm buying this as a work truck for work that could end at anytime, I want my decision to well informed.


Thanks!

[JSteward]

I should probably add:

I drive 1000 to 12000 miles per week. 1/2 the time travel is over hills.
I almost never tow, but once or twice per year I'll tow my 8000lb travel trailer.
I'm working in the deserts of southwestern Wyoming and need 4x4 for winter.


Thanks for any comments or suggestions!

[Prestonia24]

1000 to 12000 miles a week????? Wow thats a lot of miles...

I'm sure that you'll get much better fuel economy with a newer DMAX than your 6.5.

I have an 06 K2500 CC and i just love it. I'm getting better gas mileage than my old C1500 did, and have much more truck. I don't have anything to tow, but when some hauling work comes along the Duramax doesn't even sweat.

Personally, I went with the 06, and not the 07 because of the emissions restriction, and not the 05, due to the older motor (LLY), the LBZ makes plenty of Power and Torque (360/650) which is sufficient for most people.

I'm sure that with the amount of miles that you drive on your truck the reliability of Diesel, and a newer truck with warranty, will certainly help you out.
Also, i've been getting progressively better mileage as the truck gets broken in, i'm at 7700 miles and getting nearly 16 street and 22 highway.

What kind of stuff will you be hauling in the truck?

[beeler]

If I were in your shoes I would buy a gas burner. I too had a '96 6.5. It was in the shop constantly and Chevy bought it back. Went to a '98 454 and then to a '02 Dmax. While I do like the Dmax and it has 110,000 relatively trouble free miles, I almost wish I still had the gasser. Like you I tow a fiver with a small toy trailer behind a total of 2-4,000 miles a year. That's where the Dmax shines. I doubt I'll ever pay for the diesel in milage savings, so the only other advantage is resale.

My 6.5 with 4.10 gears made 16 mpg highway. 454 around 12 and Dmax 17. If I was you I'd pay at the pump and let someone else worry about the extra upkeep on the diesel.

[rob from bc canada]

Most people buy diesels because they like them, and try to justify it by savings, which is a bit hard to do.

If you drive a lot of miles, per your post, I'd go with the Diesel, but only if I could afford a relatively new one, and make sure it is properly maintained. That way, you can get lots of miles out of it, and it will pay for itself eventually.

Driving mine around the Island here, it's nice to only have to fill up about every 800-900 kms (500 to 560 miles). Tons of power when I need it. Enjoy that allison tranny - come down from the ski-hill without hardly using the brakes.

However, if you're tight for cash and can't find any 0% financing like they were giving here when I got mine, I sure wouldn't borrow the extra capital cost, and expect it to pay back the interest.

05's are great trucks unless you plan to tow large and heavy in high temps, in which case you can modify the cooling system for about a grand. 8000 lbs on the prairies should be no problem at all. Injectors are much easier to change if they ever cause problems.

[BozDMAX]

Before I purchased, I did a cost analysis of the breakeven point of buying diesel vs. a gasser. That was back in late '02 with the LB7 engine option running $4300 over the gasser.

At the time, I estimated 9MPG for the gasser and 15 for the diesel (my father gets about 9, my actuals average 14.5 for the first 125K miles).

I estimated $1.459 for diesel and $1.659 for gas and came up with a breakeven point around 50K miles.

Since then, diesel fuel is through the roof, usually 20 cents MORE than gasoline if I am lucky, so the calculations should change considerably.

Given the same option price and assumptions on MPG (9&15), fuel prices at $2.569 for diesel and 2.359 for gas, the breakeven point would move to...
about 47K or so - not really what I would have predicted.

I don't know the current option price for the DMAX engine, nor am I as comfortable using 9MPG for the gasser. I would have guessed the switch of diesel getting more expensive than gas would have a bigger impact, so I will keep looking at my calcs, but I still figure a breakeven of about 50K is worth the cost.

If you are going to do any significant heavy towing, the decision is pretty clear based on technical considerations alone. Even not towing, the diesel is going to last longer and retain it's value better than the gasser when you (or if you ever!) decide to sell.

Something tells me I will not sleep well tonight trying to figure out why the price changes in fuel did not have a bigger impact... Course, who cares? I really WANTED the diesel no matter what!

[JSteward]

Thanks guys... I'm almost convinced to go with a gas powered 3/4ton single instead of the diesel 1ton dually...

Now, to decide what company to go with....?


-Jason

[JSteward]

1000 to 12000 miles a week????? Wow thats a lot of miles...

I'm sure that you'll get much better fuel economy with a newer DMAX than your 6.5.

Personally, I went with the 06, and not the 07 because of the emissions restriction, and not the 05, due to the older motor (LLY), the LBZ makes plenty of Power and Torque (360/650) which is sufficient for most people.



So, the LBZ is the best engine for fuel economy...? And that engine is only available in the '06? Is that in all '06? If so, that sounds like the way to go... but I don't need a new truck. I'd be satisfied with something well priced. What about the older DMAXs? Is there a difference in engine models in these that may provide better economy?

Thanks

[Quack_Addict]

So, the LBZ is the best engine for fuel economy...? And that engine is only available in the '06? Is that in all '06? If so, that sounds like the way to go... but I don't need a new truck. I'd be satisfied with something well priced. What about the older DMAXs? Is there a difference in engine models in these that may provide better economy?

I think part of the fuel economy increase of the `06 LBZ over the LB7's and pre-2006 LLY's is due to the 6-speed Allison behind it with 6'th gear being a second overdrive gear. Through the `05 model year, the Allison was a 5-speed with only one OD gear. To the best of my knowledge, the 5 & 6 speeds are pretty much the same with exception of the valve body and TCM flash. I have seen a retrofit kit that comes with a new valve body and TCM to convert 5-speed Allisons to a 6-speed. The LLY engine was available in 2006 with the 6-speed Allison differing only in HP and torque from the LBZ.

The LBZ was only available in 2006 under that RPO because of the emissions changes that took effect for 2007 model year vehicles. I have not done much research on it but have taken a few passing glances at a 2007 GMT900 with the LMM Duramax and it looks similar to my LBZ in most regards other than the exhaust system and it seems the intake baffles are different.

My brother claims to know someone with a 2006 LBZ that with an economy chip installed that's giving him high 20's to low 30's for fuel economy but I can not confirm. The best I have seen with my LBZ so far is around 21 on the highway, unloaded with just over 8k on the odometer and I plan to keep mine stock.

[Kennedy]

You won't find a CC Long Duramax Allison as I bought them all! :D

Seriously though people have forgotten what a long bed is. As for economy by engine series, I have all three. At present I give the edge to my 05LLY over the 02, but the 02 has been souped up substantially and has modified injectors. It will still knock down 19-20MPG. The LLY is running 20-21+ if I behave. Yes it does have the 6 speed conversion now, but I don't attribute any huge MPG gains to the lower cruise RPM. My LBZ (not broken in yet) hasn't shown me a verified 19mpg yet. I've been able to tune in verified shifts in MPG (nearly one full MPG) with my tuning, but 18's is all it wants to do at present. I have taken a different approach with this one though as it retains factory stock exhaust and air filters for the time being.

Before anyone says cold weather and winter fuel, my 05 will return 20+ pretty darn easily most any day and it's a pretty good sized truck.


With a Dmax (not trying to scare you or anything) you need to note that they are VERY expensive to fix if they do have problems out of warranty and most major repairs are beyond the capability of the average Joe. Thankfully they carry an excellent warranty and have in most cases provided exceptionally good reliability. My 2002 had a water pump under warranty and my 05 has only had batteries under warranty.

That said, reading the tone of the original post, I'd suggest looking at the LLY or LBZ used, and maybe consider the LBZ Classic brand new for the 100k warranty and current programs running...

[Kennedy]

My brother claims to know someone with a 2006 LBZ that with an economy chip installed that's giving him high 20's to low 30's for fuel economy but I can not confirm. The best I have seen with my LBZ so far is around 21 on the highway, unloaded with just over 8k on the odometer and I plan to keep mine stock.

I can about guarrantee you that this 30mpg claim is a guy reading the DIC calculator and not hand checking.

[mschuyler]

I can about guarrantee you that this 30mpg claim is a guy reading the DIC calculator and not hand checking.

OK. But is there an "economy tune" to be had?

[SoTxPollock]

I wouldn't believe 30 mpg on any size truck with a duramax of any description. Ain't gonna happen. Based on what I've read, your best bang for the buck would be a 2006 LBZ who knows someone may have traded one for a 2007 just because they liked the way the 07 looked.
You could always buy Kennedy's 05 if its still for sale. You know it would be bullet proof dependable.