I have a set of OEM 15's and 16's wheels/tires...the 16's are about 12 pounds heavier (each) than the 15's, but ride nicer and are stickier.

OK...

bigger/wider wheels mean better handling, and in at least some cases, a better ride too.

But...

What about MPG's?

FIRST, weight:

Generally speaking, is a 15-inch wheel (assuming it's lighter) ALWAYS going to get better MPG's than a 16 or 17 with an equal rolling-resistance tire? In other words, I'm just trying to isolate weight here. If so, how much, are we talking .1 mpg, or are we talking 1 or 2 mpg?

SECOND, rolling resistance:

Generally speaking, will a 15-inch tire have a lower rolling resistance than a 16?

FINALLY, questions:

ONE:

What is the best wheel size and tire combo, for MPG...and as a second priority, a nice-ish, quiet-ish ride. Do the "low rolling resistance" (LRR) tires really make a difference? I'd imagine a MINI would be slightly faster in a straight line with LRR tires.

TWO:

How much more MPG can a MINI get with the right wheel/tire combination, but at what cost in handing, ride, etc?

Thanks...

 

Narrow...light....low rolling resistance....but it is all about compermise....also keeping the actual diameter of the tire close to spec so the gearing is not thrown off....
Sounds like you kinda answered your own question....you just need to decide how much mpg to sacrifice to gain fun or view versa!!ps....not much testing has been done...but imo it is likely about 1 mpg or so total in normal combo's...more in extreme cases....and low rolling resistance tires are usually NOT GRIPPY....

 

In trucks tires in the same size is said to be good for about a quater mpg (getting about 6 mpg)...but remember...a new low rolling resistance tire has more resistance than a worn older tire...rubber squirm...
Compared to a heavy 18 rim, the diff is signafigant...15 to 16..not so much...but I know I get better mpg's on my 16's tha folks in their 17+ rim tire combo's..

 

Yep...that's what I need...to know just how many mpg's can be gained....the whole low-rolling resistance tire thing isn't worth it at .5 mpg, but at 3 or 4? Maybe...

 

The following should give you better mpg:
Narrower tires for less friction (since smaller rims generally have narrower tires, there is a correlation)
lighter rims also correlated with smaller rim sizes generally
Low rolling resistance tires

Out if those, I think that Better driving habits wins hands down.

 

I agree.

But better driving habits AND the better tire/wheel combo will do even better.

But from what folks are saying, it sounds like 15-inch wheels, with low-rolling-resistance tires are the best.

Still the question remains...how much of a difference does that combo make?

 

I went from 175/65/15 to 205/55/15 and acheive the same gas mileage. I am getting 39 mpg. I have them mounted on the stock 5.5 inch Mini Spooler wheels. They run almost exactly the same diameter as the stock tires.

 

It's been estimated that LRR tires could save 1.5 to 4.5% of the gas we burn while driving. Going by that, one's usual 30 mpg should jump to 30.45 - 31.35 mpg just by switching to LRR tires (all else remaining constant, of course). That's not much of a gain for just one driver, but if 100 million Americans did it every day ......

When considering 15" versus 16" wheels, and a little narrower versus a little wider tires, we can expect to observe only very small changes in mpg. Thus, I agree with slinger's claim above (post #5); staying within the normal range of wheel/tire choices we usually make, the biggest mpg gain we can get is by adopting a more fuel efficient driving style. It's not much fun, but it works.