Re: Fuel grade question...

Posted by Tim Cole On 2012/8/17 16:31:42

For 1951 Packard was recommending high octane for the engines with Ultramatic and regular for manual transmission cars. By 1954 they recommended premium for everything; the 288, 327, 359 and the V-8.

How did they make these recommendations? They drilled and tapped knock sensors into the block, took the car out on the test track, and recorded the knock readings on special meters inside the car. Or they did it on a dyno. Or both.

The reason modern cars generally run great on regular is because a computer controlled engine retards the timing to accommodate the grade of gasoline. And the owner's manuals will sometimes state that optimum performance will be achieved with higher octane, but that regular is acceptable.

Now those old gasolines used tetraethyl lead which was a very effective, and cheap, anti knock compound. I don't know what the octane ratings were in those days, but I'm sure they can be found. However, the octane number methods are subject to change.

Suffice it to say the Packard owners manual is the appropriate source for deciding what grade of gasoline to buy. Notwithstanding that the cars burn so much of it.

I wouldn't tell somebody to disregard that recommendation.