Comments on: Driving More Miles Using Less Fuel http://www.youngmoney.com/wheels/misc/060817_53/ Money: Earn it, Invest it, Spend it Fri, 16 Mar 2012 19:14:29 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: oddtyme http://www.youngmoney.com/wheels/misc/060817_53/comment-page-1/#comment-870 oddtyme Fri, 06 Mar 2009 15:42:22 +0000 http://75.145.89.9/?page_id=53#comment-870 The science in this article is very weak: While cruising (ignoring starts and stops), the engine burns fuel to overcome various forces of friction and drag acting on the vehicle. One of those is friction between tire and road, another is air friction, another is friction within the engine, and the other main source of drag is the engine sucking vacuum when running at partial throttle. The amount of engine vacuum drag is a function of the engine RPM and the how much the air is restricted at the throttle plate. By increasing the tire diameter, this does reduce the speed of rotation (in terms of RPM) at the wheels and thus also at the engine. So, the amount of engine vacuum drag is reduced proportionately, and there is some increase in MPG. BUT, this is only one source of drag/friction out of many. To suggest that a 12% reduction in apparent miles travelled, as per the odometer, translates into a 12% fuel savings is simply false. Taking this article's logic to the extreme, we should all have 40 inch wheels on our car so that we can reduce our collective fuel consumption by 75%, and thus solving America's energy independence problem. The science in this article is very weak:

While cruising (ignoring starts and stops), the engine burns fuel to overcome various forces of friction and drag acting on the vehicle. One of those is friction between tire and road, another is air friction, another is friction within the engine, and the other main source of drag is the engine sucking vacuum when running at partial throttle.

The amount of engine vacuum drag is a function of the engine RPM and the how much the air is restricted at the throttle plate. By increasing the tire diameter, this does reduce the speed of rotation (in terms of RPM) at the wheels and thus also at the engine. So, the amount of engine vacuum drag is reduced proportionately, and there is some increase in MPG.

BUT, this is only one source of drag/friction out of many. To suggest that a 12% reduction in apparent miles travelled, as per the odometer, translates into a 12% fuel savings is simply false. Taking this article’s logic to the extreme, we should all have 40 inch wheels on our car so that we can reduce our collective fuel consumption by 75%, and thus solving America’s energy independence problem.

]]> By: Steve http://www.youngmoney.com/wheels/misc/060817_53/comment-page-1/#comment-812 Steve Tue, 17 Feb 2009 18:07:12 +0000 http://75.145.89.9/?page_id=53#comment-812 If the car speedo shows less then the car (DRIVE TRAIN) moved less! Good Idea..some things are worth trying. A wider tire would have hurt mileage, Taller to a degree will get you farther on the same gas, Highway. If the car speedo shows less then the car (DRIVE TRAIN) moved less!
Good Idea..some things are worth trying. A wider tire would have hurt mileage, Taller to a degree will get you farther on the same gas, Highway.

]]> By: nenobosi http://www.youngmoney.com/wheels/misc/060817_53/comment-page-1/#comment-538 nenobosi Wed, 12 Nov 2008 11:14:45 +0000 http://75.145.89.9/?page_id=53#comment-538 I belive that this is one of the ways to save on fuel. Persomaly I use MPG tabs which give me 12% more millage (+-10% mistake) and 65% less exhaust gasses. I belive that this is one of the ways to save on fuel. Persomaly I use MPG tabs which give me 12% more millage (+-10% mistake) and 65% less exhaust gasses.

]]> By: Adam Reiner http://www.youngmoney.com/wheels/misc/060817_53/comment-page-1/#comment-310 Adam Reiner Thu, 04 Sep 2008 10:31:42 +0000 http://75.145.89.9/?page_id=53#comment-310 "When I purchased a larger set of tires for my car, rather than the usual 42 miles from my home to my office, my speedometer read 36 miles" How does this logic work? If the distance from home to office is 42 miles, it is ALWAYS 42 miles, regardless of what tire size you have or what your speedometer says. You may "think" you're saving fuel but in reality your speedometer is not calibrated correctly to the different tire size. “When I purchased a larger set of tires for my car, rather than the usual 42 miles from my home to my office, my speedometer read 36 miles”

How does this logic work? If the distance from home to office is 42 miles, it is ALWAYS 42 miles, regardless of what tire size you have or what your speedometer says. You may “think” you’re saving fuel but in reality your speedometer is not calibrated correctly to the different tire size.

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