Re: Can I hold off on the tune up at 90K?
I tried to get my plugs changed on my 2002 starting at 90,000 miles, and both times they did the other minor chores, and refused to change the plugs, claiming it wasn't due till 120,000 miles. Got my goat, because it's my car. At around 110,000 miles I told them i was going on a long trip and wouldn't be back in time, so they replaced them. Never any CEL; never any performance issues.
I get around 24 mpg at a steady 70mph, as long as I don't run into a head wind.
In Mexico, there is a long stretch in one weird state where a high speed highway has a speed limit of 50 mph. I have never been able to check the gas mileage at a steady 50 mph, because it doesn't use enough gas in that 100 miles or so to calculate by the gas gauge how much it used. I wouldn't be surprised if it got 28 or more at that low speed, but no way to find out.