I have had my 2004 is300 for 6 months now and my only complaint is it burns too much gas. With gas prices on the rise can I get away with filling up with 87 oct.
thanks

Most of us agree that we wouldn't use anything but premium gas. There is much discussion of that here.

Will it break the car if i don't use premium gas??

Sooner or later it will be all carboned up. In the short run it won't run as well because the timing will retard, and under severe conditions such as lots of hill climbing it may ping from pre-ignition knock. The mileage probably will drop off to where you're not really getting any appreciable savings, all at the expense of performance and engine life. The car just wasn't designed for regular gas. There's a lot of IMHO here but all that I have stated is based on facts.