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Auto Q & A
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Posted by editor Wed May 17, 2006 12:06:20 PDT
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0 responses 0 comments Dear Q & A: In connection with your discussion of whether leaving the tailgate up or down in a pickup truck would give better gas mileage, I thought I’d share my experience. On a recent trip to Utah in my Ford F-250 with the 460-cubic inch V-8 engine, I got 15.6 miles per gallon. This was far better than the 11 or 12 mpg I got covering the same route some months ago. The only difference was that this time my truck had a camper shell mounted and I’m assuming this was responsible for the better fuel mileage because of lower wind resistance. You agree?

Dear PH: Agree. Adding the camper shell, despite its extra weight, eliminates the air-dam effect of the vertical tailgate. A fiberglass bed cover would have done the job even better. Yours is anecdotal evidence, of course, so don’t bet the farm on it, but it’s consistent with other reports and with sound science.

Dear Q & A: My husband is a few months short of 80 and maybe a few cards short of a full deck. I say that because he likes to drive (too) fast, 70 on two-lane roads and 80-plus on Interstates. He says don’t worry, he’s always watching for police cars. How can I get him to slow down to normal speeds? 

Dear Scared: Police cars are the least of his worries. At 80, his reflexes aren’t what they were when he was 40, although his right foot evidently weighs about the same. All it takes at 70 on a two-lane road is a moment’s inattention or a blowout (from that weak spot on a front tire he was unaware of) and his car could wind up a smoking ruin in a ditch or wrapped around a pole. With you in it. He may like to pretend he’s training for Indy, but put it to him this way: Does he care enough about you, who trusted him enough to marry him, to keep you from getting killed or maimed needlessly by a foolish, irresponsible driver? Besides, faster means fewer miles per gallon.

Dear Q & A: How do I convert liters (as in a 3.8 liter engine) to cubic inches and vice versa? Some car engines are described as having cubic inches displacement and other engine sizes are shown in liters, or like motorcycles, in cc (for cubic centimeters). Is there an easy formula, where I don’t need higher math, for conversions between cubic inches and liters?

Dear Harlan: Here’s a quick rule of thumb for converting either one to the other. If the engine size is given in liters (say 5.0), multiply the number by 6.1 to get the equivalent CID of 305 cubic inches. To reverse this, if the size is expressed in cubic inches (say 350), divide that number by 61 to get the size in liters (5.7). It’s not absolutely precise but suffices for practical purposes. By the way, a liter is equal to 1,000 cc, so simply add three zeroes to convert liters to cubic centimeters.

Dear Q & A: Why do some cars have two or four tail pipes? Do they help push the car forward faster through the air?                    

Dear Just: Like the decibel number of the noise emitted through the tailpipe(s), more and bigger pipes are intended to elicit admiration from onlookers. While mostly just a prestige factor, there is a core of reality. Every engine must breathe both in and out and more powerful engines need to be able to vent exhaust gases in greater volume than weaker, smaller ones. If Joe mounts two or four big megaphones under his rear bumper, we’re supposed to think he’s got a mean machine. But things are not always what they seem. And no, the push factor is miniscule.

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