"Actually last week I saw a guy filling up his brand new IS300 with 87
at Arco while doing a beer run and all I could do is shake my head
at him. What a shame"
Not a problem. Since about the mid-nineties all high compression engines have knock sensors and multiple spark maps at least one for premium grade octane level and one for regular grade octane level. High compression cars will run fine on regular grade fuel. Sensitive drivers might notice a small drop in performance due to the less aggresive advance curve, especially low end torque, but most drivers can't tell the difference.
Originally posted by tigeroscar1
Yesterday I was driving from Las Vegas to Albuquerque for a class. My 260E was running like a champ. I stopped to fill-up at a Chevon. About a half hour later the engine started to sound rough and the economy needle went into the red and the Tachometer rpms also went higher. Gas mileage went form about 24mpg to around 10-15mpg !! Just starting the car the economy is in the red.
Your engine appears to have developed a problem, but it's very unlikely it has anything to do with the fuel. Most markets have fuel blends that are regulated, and the difference between brands is very slight - usually just the additive package, but the base stock is the same.
The additive packages are not regulated, but there are tests such as gum and varnish formation and deposit buildup that each additive package must pass.