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Old 05-10-2013, 04:12 PM
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Cost/benefit for gas and diesel.

OK, I've sat down and tried to juggle some numbers for cost of driving between gas and diesel so that we can actually what we gain using one engine over the other. Since I am no math whiz, please correct any flaws you see.

Let's assume gas:

3.6 should get 20 mpg on mostly hwy; 5.7 Hemi can get 18 mostly highway, and the diesel should get 27 mostly hwy.

If we also use $4.00/gallon for gas and $$.30 for diesel, we'd get

.20/mile for the 3.6

.22/mile for the 5.7

.16/mile for the diesel.

A definite savings of 6 cents per mile over the 5.7 Hemi.

However, the diesel option is $4,500 + 7.5% tax (not counting in any interest on a loan) that would make the option $4,837. A savings of 6 cents per mile will take 80,000 miles to break even.

If you tow, fuel mileage decreases and the diesel might get 20 mpg or less, but of course the diesel's better torque will make towing easier. If we
calculate towing's drain on diesel, we would also deduct the same if towing with gas. The issue is the differnece in cost as opposed to what each would cost independently.

If we also factor in DEF fluid costs, higher cost of oil changes, fuel filters, additives, the savings may be closer to 4 cents per mile difference and even more than 80,000 to break even.

Does anyone see this differently?
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Old 05-10-2013, 04:22 PM
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Re: Cost/benefit for gas and diesel.

Pretty Close.

I agree with your math on the most part just two minor comments.

I know from past experience that the diesels are more capable of exceding thier mileage specs than a gas engine and certainly the Australians are seeing some awesome highway mileage even with the 5 speed.

Slightly more major issue is though that I don't think most people are looking just between the V6 and the Diesel. If you are than YES absolutely the payback will be long but when you compare the price of the upgrade against the Hemi which is I guess now $2305 because of the price increase than your payback is much shorter.

Don't get me wrong, I see what you are saying and people shouldn't say hmmm... should I go from the 3.6 to the CRD to save money in the long run. That would take a while for sure. People thinking V8 sure but then the comparison in upgrade should be against the V8.

EDIT: Also I forgot, IF you do tow.... Diesel "drain" pentalty is about 10% less than a Gas engine so for example in the real word a comparable diesel would be 40% better while towing than a similar gas engine in real world driving.
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Old 05-10-2013, 04:40 PM
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Re: Cost/benefit for gas and diesel.

Looks like the Aussie's are getting between a little over 26mpg mixed. all the way to 35mpg for all highway and all of these guys are reporting under 7000 Miles.

WK2 Deisel Economy

*** I want to point out though this is with the 5 Speed and I expect better from the 8. I also asked about how they are finding the engine.

Still not arguing against the V6 comparison though.
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Old 05-10-2013, 04:42 PM
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Re: Cost/benefit for gas and diesel.

Thank you for the insights. I figured I'd keep the variables as few as possible and keep as much consistent. Anything more than 2-3 variables and everything is out the window.

My point is that it will take quite a while to achieve a positive cost savings---how long a while will depend on too many factors, but even with some variability, I would say 60,000 to 70,000 miles before break even seeing it most favorably for the diesel.

I had figured my Ram Cummins 3/4 ton would not break even before 200,000 miles. I was hoping the Ram would have lasted to be my forever truck....but it was not meant to be.
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Old 05-10-2013, 04:50 PM
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Re: Cost/benefit for gas and diesel.

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Originally Posted by ms.annthrope View Post
Thank you for the insights. I figured I'd keep the variables as few as possible and keep as much consistent. Anything more than 2-3 variables and everything is out the window.

My point is that it will take quite a while to achieve a positive cost savings---how long a while will depend on too many factors, but even with some variability, I would say 60,000 to 70,000 miles before break even seeing it most favorably for the diesel.

I had figured my Ram Cummins 3/4 ton would not break even before 200,000 miles. I was hoping the Ram would have lasted to be my forever truck....but it was not meant to be.
Yes, well these should break even before the warranty is up on the drive train. RIP on the Ram friend. I fight hard for the little Diesels because I came from driving Duramax 6.6 and it is such a different world. The real world driving efficency is insane (especially when you are driving on Southern Interstates = Faster)

You know what I want to see is real world fuel consumption testing. MPG that is actually middle of the road on Gas engines. I have to drive like I am 82 and can't see farther than 300 feet in order to get the published numbers on the Durango!
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Old 05-10-2013, 05:19 PM
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Re: Cost/benefit for gas and diesel.

You need to figure depreciation on the diesel vs gas. You may get some of the diesel price premium back when you sell the vehicle.

I just looked up 2011 Touareg gas and diesel on Edmunds. In the Sport model (least expensive trim) the diesel brings $1112 more on trade in. It costs $3500 at MSRP more when new.
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Old 05-10-2013, 05:30 PM
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Re: Cost/benefit for gas and diesel.

Are the Aussie Jeep diesels choked out with all the EGRs, particulate soot filters, diesel burn offs, DEFs? They really lowered fuel mileage in the 3/4-1 ton diesel trucks. Ram Cummins used to get 22-24 mpg, they now get 18-20 mpg tops. If Aussies are not requried to use those dang EPA mandated emission controls, that may explain why they are getting good mileage or why it may hurt US Jeep diesel mileage.

I didn't factor in resale because my head would explode. Resale on diesels will also depend on city or semi rural. Diesel fuel in a city is hard to find, perhaps 1 in 8 stations carried diesel. I would tank up before hitting Los Angeles and tank up at 1/3 down. Once I got back out of the concrete jungle, diesel was at every other station. That may vary whether diesel carries a good resale or not.

VW Toureg used to have that insane 5 liter V-10 oil burner cranking out 300 horses and 500 foot pounds of torque! Now that's a diesel I would love to have! Use that diesel in a Toyota Land Cruiser and get the price down to where mere mortals can afford it, and I would go right back to Toyota.
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Old 05-10-2013, 05:52 PM
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Re: Cost/benefit for gas and diesel.

Trying to predict fuel costs and economics on the diesel vs gas is an interesting but fruitless comparison, IMHO. Been there done that. Its only practical use is justifying whatever decision you want to make.

5 Years from now, all the basis of your comparisons could be changed. If you are lucky enough to get a trouble free diesel for 200,000 miles it does make sense, but its a lottery. You could probably buy an entire gas engine for the same price as replacing the injectors on the diesel.

Not only is there a premium entry fee (in the states) Diesels do cost more to maintain and repair if needed.

So base your decision on what you need or want... forget economics. Simple as that. Do you like the performance, the towing capability, the sound.... Other areas of the world have different decision criteria with subsidies for different fuels.

A decade ago when diesel fuel was 1/2 gas in the states and for those folks intended to drive their trucks 300,000 miles in less than 10 years, it was different.

Today I would never buy diesel based on economics as it is such a crap shoot. Electronic injectors get held open with a tiny micron particle, fuel washes down the cylinder walls, $7000 in engine repairs.... let it get too cold, fuel gels, a $1000 clean up bill.. let the EGT run high, you've blown a $5000 turbo... Of course you can rationalize away much of this as it will never happen to you, but you are just kidding yourself on the economics (Stateside).
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Old 05-10-2013, 05:55 PM
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Re: Cost/benefit for gas and diesel.

Quote:
Originally Posted by ms.annthrope View Post
OK, I've sat down and tried to juggle some numbers for cost of driving between gas and diesel so that we can actually what we gain using one engine over the other. Since I am no math whiz, please correct any flaws you see.

Does anyone see this differently?
I do. I definitely do. I do not have the strength to repeat myself so I will simply try and reference my older posts. Starting with your assumptions:
  • the fuel economy difference between gas V6 and diesel is greater than what EPA has measured - for highway only. Or city. And since nobody has driven real life diesel with the new 8 speed transmission and reported back , we should really stick to the EPA numbers.
  • the diesel option is not really only a 4000 dollar option. It is more so because you have to add LUX or ADV. TECH packages depending on whether you are buying a Limited or an Overland. In other words you cannot buy a simple Limited or Overland with the diesel engine option - you have a forced upgrade that some people may not really want or need. For instance LUX PKG (I have it) was not worth 4000 dollars or whatever it was but I had to buy it to get the ADV. TECH. for the wife. I don't need the larger sunroof - I wanted it without. Vented seats ? Nice but not needed. HIDs? 100-200 dollar aftermarket purchase - definitely not as nice but lots more light and it can be done right and tastefully.
I have attached an Excel Spreadsheet. It is inside the ZIP FILE called Gas vs. Diesel. Go to the TAB that is titled 0.25$/year and play around with the values in the YELLOW Cells. Change the values for miles/year driven in City vs. Highway; play around with the fuel economy; with the difference between diesel and regular (or premium gas); the average cost of fuel in your area etc.


You will see that fuel economy for the diesel is over-rated when compared to the V6, you will be highly unlikely (realistically never) to get your money back by buying a diesel. Then there are the maintenance costs which are - safe to say - higher for the diesel. And to think that you would be getting that $4000 back when you sell the car? Seriously? 1000 $? Yeah I could see that. You lose $ 4000 after a week of driving it away from the showroom floor. Five years from now ithat initial price difference will be worth a lot lot less.

I've said it before and I will repeat it: buy the diesel for the torque, for towing the boat or the trailer; for off-road. NOT for fuel economy.
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Old 05-10-2013, 06:31 PM
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Re: Cost/benefit for gas and diesel.

We're actually on the same page presenting the position that any anticipated "savings" in buying a diesel may be a illusory.

And ColdCase is absolutely correct, the cost of maintaining a diesel can be a wallet wrecker. Any work on a diesel requires a diesel mechanic and any work is expensive. The new high pressured Piezo injectors at 29,000 PSi can be damaged if some micro particle gets sucked into the pipes nad blast out the nozzle. Blown turbos, I've brought up the issue of cold diesel gelling and cloggin the systsem, etc.

Much for anyone considering a diesel to ponder.
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Old 05-10-2013, 07:24 PM
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Re: Cost/benefit for gas and diesel.

Agree the comparison should be Hemi vs Diesel. If the V6 is "enough" than that should be the choice. If gasoline goes away you might be able to use a still.

Second, does anyone know what the axle ratio is for the diesel setup in OZ ? If 3.09 then top will be about the same as top in the 8-speed with a 3.45. That would make a highway comparison valid.

US emissions will be a factor. Since a diesel runs at WOT all of the time (and boosted under load) how does the EGR work ? In a car it relies on manifold vacuum at cruise. YWTK.

Other than that it seems to be more of a catalyst/afterburner and the question is do the emissions controls rely on back pressure and an over rich mixture ? That could kill MPG.

Just a few thoughts but bet we will see some with "my other car is a Prius" stickers.
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Old 05-10-2013, 07:40 PM
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Re: Cost/benefit for gas and diesel.

I could not get the photo to be viewed upright (sometimes Apple really annoys me). But as you guys can see, there is currently no difference between midrange and Diesel in my area.
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