make the car heavier to gain mileage?!

[bgd73]

as the title states. It does happen.
As some may remember the crazy wobbling inline transverse of yester year (now unlikely to be so sloppy), when motor mounts were tightend, body structures failed.
As we all do not live in paradise for sheet metal, I do not know of a failure that isn't possible, to this day.
I recently have been working with a 21 year old subaru. knobby tread, 15 inch wheels, AWD 5 speed dual range, and a claimed weight of 2300 pounds. After doubling the rocker panels, adding frame work, wheel wells, rear quarters, all welded...I gained fuel mileage. The frealy little car sounds like a monster truck with the thumping studless snow tread on the hot tar at 35mpg.
the engine became a rock in its spot. It occured to me...short stroke little engines lose for every movement against thier fire stroke. Adding roughly 21 pounds of steel permanently in strategic locations of structure added fuel mileage, regardless of my -20s F winters to 90 degree july.
A thought to ponder no doubt....
Of course boxers and inlines do many opposites, and fuel injection may like the shaking, I am working with a carb original 1781 cc boxer. Smooth tread is back in the
high 40s mpg on the highway.
Just thought I would throw the idea out there if anyone has reached a dead end with thier little engine being a hog for no apparent reason. This is an odd reason, but worth a mention.

[ebacherville]

really if you hade very flat terrane the weight would mean nothing.. my terrane slightly hilly weight means alot.... weight over all decreases effiecency.. more weight is harder to get going .. but allows for more coasting ability.. however most people dont coast nearly what they can in there cars.

[jamesqf]

Originally Posted by bgd73

Adding roughly 21 pounds of steel permanently in strategic locations of structure added fuel mileage...

Even if your theory's correct, though, it's not the 21 pounds that increased the mileage, it's the added stiffness. If you could have somehow added the same stiffness with zero weight increase, you'd do even better.

[Shawn D.]

Originally Posted by bgd73

the engine became a rock in its spot.

[wagonman76]

Ive been wondering that about my Celebrity. I took at least 150 lbs out of the trunk, and still got 32 mpg going downstate and back, just like before. I notice that the back end sits up a little higher now since the springs are not as compressed, and maybe that added wind profile offsets the weight decrease. Some cheap lowering clips on the rear springs might tell the tale of whats really going on.

[garys_1k]

Originally Posted by wagonman76

Ive been wondering that about my Celebrity. I took at least 150 lbs out of the trunk, and still got 32 mpg going downstate and back, just like before. I notice that the back end sits up a little higher now since the springs are not as compressed, and maybe that added wind profile offsets the weight decrease. Some cheap lowering clips on the rear springs might tell the tale of whats really going on.

Changing weight makes comparatively little difference on highway FE (relative to city). If you're running stop and go traffic, or running up inclines, then extra weight will make a significant difference.

Also, in your case, that 150 lbs. is likely only 5% or so of the total weight. That may have improved things but you'd need to average a number of tanks to see that subtle a difference.