It depends where you live and if you have had the cylinder heads redone. If nothing has been done to the heads you will need to get a lead additive because today there's only unleaded gasoline. Up until the late 70's early 80's lead was used in gasoline and lead is what lubricates the valve stem sleeves (if you live in California you're s.o.l.). If you've had the heads re-sleeved then you can run gasoline with an octane of 87 to 94. I would recommend using higher rated octane due to the fact that the 283 has a 9.25:1 compression ratio. I have a 283 that's been overhauled and I use try to use 89 or higher. Anything lower than 89 may cause knocking. In conclusion I would use 89 for driving around town, 91 for long trips, and 91 or higher for racing. And if you find a place that sells 94, it'll cost an arm and a leg.
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