Replacement Tires??

My certified Hybrid mechanic said it is best to replace all four because of the way they wear. if the back tires are uneven from the front it can cause problems.

Up here in Canada where we get some serious winter I replaced the stock Eco's on my 07 FEH AWD with Goodyear Tripletreds. I found the tire to be a great snow and ice tire (great ice traction) and also quieter than the Eco's. I did run them all winter, with about 38psi in them, tho sidewall says they can take up to 48 and I must get around to putting 44 in them (don't want to run too hard!). Mileage wise, well, hard to tell yet, barely into one tank of good summer weather, having been away in another vehicle for almost two months. I'm guessing, and it's a rough guess, at present psi prob 2mpg hit. However, even at current pressure the vehicle seems to run out well when I coast. I would call myself a 'mild hypermiler' as I try some of the tricks, but I need at least one tank (my current tank would have been run half in colder weather that two months back is saying 9L/100) in this good summer weather and more air in the tires to see how these tires rate mpg wise. With the Eco's last summer I sometimes got to 7/100 average about 7.5.

Again, in the severe winter conditions (minus 20degC and more common for weeks) of Winnipeg MB, Canada, the vehicle was barely hybrid most of the time due to the short jaunts I usually made, and often ran 12L or more/100km. Thus, cold weather, far more than the tires, was the biggest hit this past winter.

Comment from the original poster:

FWIW, after 36,000 miles we purchased a set of Goodyear Triple Tread Fortera's, and have noticed a significant jump in the handling, the quietness, and the braking of our FEH compared with the original Conti's. We have not noticed any difference in gas mileage, probably because of variation in our trips, but all the parameters (like when the engine kicks in while accelerating or coasting) seem identical. We have not had a chance to test out the traction in the snow, sand, or rain yet, but we are sure they will be far better (lack of traction and braking were two reasons we began looking for a better tire). Researching on Tire Rack, we found the Conti's had a rating of 5.5 while the Fortera's were around 8.5 -- clearly a much better tire. According to Goodyear's research, their "eco-tire" would only save about 3 gallons each 1000 miles. On a national level this may be significant (although we can "save" that much gas by driving more slowly or combining trips), but on an individual level, it hardly makes up for the extra safety and stability of the better tires.

Thanks for the comments from those who posted answers to our question.