I don't very often post here, however, i'd like to buy some new wheels and tires for my old PA.

Currently I am running fat 215/70r15 generic brand tires on 15 by 6 inch rims.
I remember when I switched to the bigger tires from the stock 205/70 r15 I saw my gas mileage take a bit of a hit. I lost about 50-80 kms a tank. Currently, I get 450-470 kms to a 53 liter fill up on average.

Last winter was even less as I had the snow tires (215/70 r15) and the fuel is blended differently.

I was thinking of finding some nice 16 inch wheels, and some new tires, p225/60 r16. I would like to know if this will improve my mileage or reduce it? I know it is a pretty common tire size as most bonnies, impalas and most GM'* i've seen wear this size. Impala'* actually seem to get awesome mileage with the base 3.4. They are also lightweight (alum frame, knuckles, etc)

It is either upgrade to the 16'* or get some new tires in the stock size 205/70 r15..

Also, what are decent tires? I'm thinking of michelin harmony or similar as I've heard michelins are designed for economy. I was also thinking of BF goodrich tires too, maybe the TA'*

Before anyone mentions it, yes i do coast as much as possible, i'm easy on the gas, keep the car in OD, and never travel over 100kph. If i drive any-more like a grampy (i'm 22) i'll prolly get pulled over.. Most driving is highway too.

The tires don't necessarily improve your gas mileage, they do change how the mileage get'* calculated and hence can make it better or worse.

For instance a higher profile tire will travel less revolution in a m/km than a smaller tire, thus recording less actual travel distance in a true mile which will affect the odometer and subsequent fuel consumption calculations.

The other factor is as you increase the tire width/height and wheel size, you add more weight. More weight does impact mileage.

If you've seen a big impact on your mileage you may want to consider replacing the O2 sensor, air filter and do a tune up with new plugs/wires if they have not been changed in awhile.

I will probably do the o2 soon actually. I think its the one that came on the car, so i definitly know its long overdue. They're not cheap, at 140 bucks for an ac delco last time i checked at the parts store here. At least i'm not paying a couple hundred bucks for some of the newer ones!

I think 16'* are as low as i'll go, i'd like 17'*, but they would never survive our roads here!