High-mileage option packages have become quite familiar over the last few years, as buyers begin to seek ways to lower their gas bills.

Ford SFE models, Cruze Ecos, HF-spec Civics and more: They're all designed to eke out an extra few MPG, using subtle but effective eco tweaks to largely standard production models.

But do these models save you enough in gas to offset the initial purchase cost? And do the unique trim packages net you better resale value?

Currently, the answer appears to be no. Kicking Tires reveals that some market analysts peg resale value at a percentage point lower than standard equivalents.

That's largely due to the extra cost brand new, while used examples sell for little more than their non-eco equivalents.

While some eco tweaks do save drivers gas--low rolling resistance tires, aerodynamic addenda, longer gear ratios and more are used to boost mpg--the improvements are often negligible.

In the case of a Honda Civic HF, the difference is only around $50 per year at $3.50 per gallon, over 15,000 miles. For the extra $700 or so you pay to get the HF over a standard 1.8 LX auto, the extra 1 mpg doesn't look like great value.

The Chevy Cruze Eco looks a better bet. Comparing the manual Cruze Eco to its non-Eco manual, 1.4 equivalent, official EPA mileage is 3 mpg better. Highway mileage is also higher, at 42 mpg versus 38 mpg.

Drivers on the EPA's fueleconomy.gov site are posting even higher figures. Most drivers seem to be using their cars largely on the highway, and the car's average currently stands at 41 mpg. Driven in such a manner, the extra $500 or so you'll pay for the Eco over a Cruze 1LT doesn't look so bad, and could be recouped fairly quickly.

Of course, this could all change should gas prices rise swiftly above the $4 per gallon mark.

Not only will differences in gas savings between regular and eco models become greater, but more efficient models may also see a spike in demand--boosting used prices.

The message here is to choose your eco model carefully. With some, you'll enjoy gas savings and lose out little when you come to sell.

For others, the extra purchase price may not be worth it--and simply adjusting your driving style in a standard model may prove to be more effective.

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