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August 2006 Better Mileage - Limited Articulation

Posted in Features on August 1, 2006
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As I write this, the price of oil has passed the $70-a-barrel mark, and $3 per gallon is the going rate at the pump. (Here in gas-hogging SoCal, we've even seen a few self-service joints posting prices over 4 dollars.) This ugly reality is starting to reflect in the mail we're receiving: "How can I get better mileage?," once seldom asked, is a question we're hearing more frequently.

Reader John Peterson writes in with an example: "I own an '89 Jeep Wrangler running a totally rebuilt 305 V-8 with an Edelbrock four-barrel and a Turbo 350 tranny. It has a 4-inch lift, 33x12.50 tires, and tons of add-ons. I love my Jeep, but now, with gas prices soaring, my wife thinks it's too expensive to keep-I'm only getting 7 mpg."

Seven mpg for something that isn't a tow rig? Not good. Obviously, we all know that we pay a mileage penalty anytime we bolt anything to our vehicles that adds weight, increases rolling resistance, or degrades aerodynamics. Larger tires and wheels, for instance, do all of these. Still, there are plenty of things we can do to help us squeeze as many miles as we can out of each gallon of fuel:

1. Regear your axles after you install bigger tires. If you don't, your engine rpm at cruising speeds will be less than optimal for best mileage. (Recalibrate the speedo too. Otherwise your odometer will fool you into thinking your mpg is worse than it actually is.)

2. Consider an overdrive unit for your juice transmission if you run a three-speed. Swapping in a stick tranny in place of an automatic will give you a mileage benefit too, but it'll cost a bit of money and sweat equity.

3. Make sure your engine and fuel-delivery system are in their proper state of tune. Improper carb jetting, clogged injectors and filters, improperly gapped spark plugs, or a worn-out 02 sensor can all degrade mileage.

4. Consider upgrading your air filter and exhaust components to freer-flowing aftermarket parts. Many can vastly improve intake and exhaust flow-and with it, mileage. They can also get you more power.

5. Use synthetic lubes. They cost more, but they do reduce wear on internals, keep their viscosity over a wider temp range, and best of all, they have longer service intervals than the dino-sauce.

6. Are your tires and wheels properly inflated and aligned? Improperly inflated rubber and misaligned wheels can be real mileage-robbers-and the heavier they are, the more mpg will suffer.

7. Install an electric cooling fan in place of the stock beltdriven piece. This can get you more power too.

8. Put your 4x4 on a diet. Are those "tons of add-ons" necessary all the time, or can we live without the lightbars, nerf bars, side steps, jerrycans, auxiliary lights, storage boxes, and so on during the winter months, then reinstall them when we need them for summer trail rides? Every pound of excess weight you can shed equates into better mileage.

9. If your rig runs A/C, turn it off if you absolutely don't need it.

10. Watch how you drive. Short trips, jackrabbit starts, and too-high (or too-low) revving can all hurt mileage.

Taken separately, each of these steps might only improve mileage by 1 mpg or so ... but if you add them up, pretty soon you're talking about real gains. We'll be delving deeper into a few of these subjects in the near future. Until then, try your best to conserve ... and happy wrenching.
-Douglas McColloch

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