1969 Plymouth Satellite gas tank question

............And yet another old annoying story from the old days.........

I was going "somewhere" I don't remember when. This is when I was stationed at NAS Miramar, San Diego. Had to gas up, pulled off the freeway at some handy exit, checked the oil, fueled up in "record time" and right back onto the freway, a "straight shot." Got 'er back up to speed and noticed considerably LESS than a full tank, WTF?? Turns out when I checked the oil, (I may have added some, don't remember) I had the trunk open. I had tossed the locking fuel cap in there and just plain forgot it. Roaring out onto the freeway, sucked about 1/2 tank right out of the filler This was the 70

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