I replaced my front left tire about 3 months ago and then the rest of the tires last month. The newest ones are all from the same company, but the one that I replaced 3 months ago is from a different company. I'm not sure if the two different tires are the same size, but they probably are since the mechanic chose the tire sizes for my car. My dad says that I should've matched all the tires though. Is this true? Should I go back and replace the unmatching tire so it'll match with the other three or does it not make that much of a difference? Also, everytime I turn on my car a warning symbol that looks like a circle divided into thirds with an exclamation point right next to it shows up on my dashboard and then disappears after a couple seconds. Occasionally it'll stay on for the entire time my car is on, and then disappear the next time I turn on and drive the car. Does anyone know what that warning symbol stands for? I looked in my car manual but I couldn't find any warning symbols that look like the one that shows up on my dashboard.. Another problem is that when I drive on the freeway, my car will occasionally feel like as if it's squirrelling around a little bit even when I'm holding my steering wheel steady. Not enough that it actually swerves into another lane automatically, but I can still feel it. Could this be due to the unmatching tires? Or could it be do the problem the warning symbol is trying to warn me about? Edit: My car is a 2005 suzuki forenza. Here's a pic of what the warning symbol looks like.