Tires: tire pressure vs gas mileage, sienna minivan, replacement tires

Question
I recently changed tires on my 2004 Sienna minivan and noticed that my gas
mileage has dropped. The only difference I notice is that the side of my new
tires are 98T instead of 96T. Do I need a different pressure in the 98T to make
the mileage better again? (Door panel states 96T should have 35, but gives no
indication for 98T). Thanks for your help!

Answer
Karen,

If you replaced the tires with the same size, then the difference in Load Index (the 96 vs 98 thing) is an artifact of the differing tire standardizing organizations in the world, but the resulkt is of no real consequence.

No, there are probably 2 reason why your fuel economy changed.

1)  New tires have more rolling resistance than worn out tires - all other things being equal.

2)  OE tires tend to have better fuel economy than tires designed for replacement tires, but you get better wear.

I explain this in more detail here:

http://www.geocities.com/barrystiretech/index.html