What grade gasoline for

an 01 Intermeccanica Super 90 1600cc engine?
Maybe a stupid question, but my BMW 2002 preferred the low grade stuff and my '87 Alfa burped on anything but Super. Need to fill up for the first time and just don't want to make any mistakes. Also, how many gallons should my tank hold.
Thanks in advance

If you have a stock 1600 cc VW engine most were initially designed to run on 91 octane. Back then that was considered low grade of medium grade. Today, in California, it's considered to be premium grade.

Wasn't the original specification of 91 for "RON or Research Octane Number" which would be different from what is called 91 now?

Good call Michael, 91 RON equals 87 MON so, use 87 or 88 for your engine

I believe what is posted on all the gas pumps in Cal is "(RON + MON) / 2." In other words the pump is the average of RON and MON. The posted number is a typical government mandate - no real relationship to anything in the real world.

Remembr the 60s technology - Go rich and add advance - until it knocks?

So if the engine "pings", up the octane or retard the spark or run the carbs richer. Carbon buildup in older engines will up the effective compression and want higher octane. I've read of VW street driven engines running compression ratios everywhere from 6.5:1 all the way up to 10.5:1. My engine runs fine on mid-grade. Yours may not.

The stock compression ratio was around 6.6 to 7.0 to 1. My 1915 got set up to have a compression ratio of around 7 to 1 and it works fine on 87 octane.

Isn't "RON - MON" a Dominican Rum & Coke ?

I had dieseling or running engine after key switched off using low grade gas.
After going to hi-test (the highest) it stopped. The few pennies don't matter it is just how your engine runs. Do some tests with different octanes.

Dave