GoshenSubaru

2014 Subaru Forester [i posted this to another forum & did not get good answers so am posting here.] I had a tire dealer tell me that if one tire is damaged and cannot be repaired, I need to replace not just that tire and its opposite mate but all 4 tires. If all tires have reasonable tread left, say 6/32 or 7/32, do all tires really need to be replaced? Or do the tires only need to be replaced in pairs - that is, front L/R or rear L/R?

I am confused on how best to negotiate with a Subaru dealer for a new Forester. I have researched prices on some web sites (e.g.: CarsDirect, TrueCar), and have the MSRP and invoice as listed on those sites. One strategy for negotiation is to make the dealer an initial offer of, say, "$200 over invoice". But isn't the problem with this strategy the definition of "invoice"? I have one number for "invoice" from the web sites but the dealer probably(?) has a different number for "invoice". So when I make my offer, I do not really know the absolute dollar number of the offer since my invoice number may be different from the dealer's. Am I not understanding something with this strategy? Comments?