For many years, diesels were considered the more economical choice in full-size trucks, and for the models the option was offered on, passenger cars as well. But with diesel prices now far surpassing even that of premium unleaded, what does the math look like now?

Well, to help try to shed some light on that subject, I put my nerd cap on and tried to crunch some numbers on the subject. Like many of my other speculative queries into areas I don't have a great deal of expertise, I should preface this post by saying that I'm not a statistician, mathematician, commodities expert or anything else that gives me any authority or credibility on the subject.

But regardless, I charge ahead, relentless in my pursuit of some semblance of the truth. First off, let's take a look at average fuel prices as of the week of March 23, 2008. Since most of the 3/4 to 1-ton gassers run on 87, we'll use that fuel for comparison purposes. Regular Unleaded is averaging approximately $3.26 a gallon, and diesel at $4.06. For argument's sake, let's assume 350 miles per week travelled. I know a lot of you drive a lot more than that, but for numbers-crunching sake, let's stick with that baseline. Let's also assume an average of 11 mpg for gasser trucks, and 16 for diesels.

So using these numbers, the monthly fill-up cost is $414.91 for a gas truck, and $356.04 for a diesel. Even assuming a slightly lower economy average of 15 mpg, the diesel still comes out ahead at $378.93 per month. So your monthly fuel savings, even when getting "hosed" at more than $4.00 a gallon, is between $33.18 and $57.03. The average diesel option, including transmission, of the Big 3 domestic trucks, is $7,751.67. For simplicity's sake, and because the LMM Duramax is now available only with the Allison, we selected the automatic option for all and averaged the price. So...if you're still with me, let's calculate the cost/benefit analysis.

Taking the cost of the diesel option into consideration, it will take between 11.3 to 19.5 years to re-coup the cost of the diesel option in fuel savings. It's a good thing diesel engines are long-lasting, because during that time, you'll have racked up between 205,660 and 354,900 miles.

Now, that kind of vehicle mileage is not unheard of for business fleets, but for private owners, those are some big miles, and I would venture to guess few private diesel truck owners keep their trucks much beyond 150,000.

So then, the answer to the question "Do diesels save you money?" Is yes, if you're patient.