Been there, done that. The battery box on my '55 is right behind the oil filler, and it makes such a handy place to set the cap down.
I had a fuel cap like this one: http://www.aircraftspruce.com/catalog/a ... elcaps.php. I painted it yellow, added some lettering to indicate oil capacity, drilled the flange to attach the safety chain that had been missing, and a year or two later it's still on the airplane!
John Renwick
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
I got the same one a year ago:
05-01057 #2 FUEL CAP ONLY UNVNTD FC2646 $8.80
Drilled a hole for the retaining chain, and printed a label that listed "8 Qts"
Corey
'53 170B N3198A #25842
Floats, Tundra Tires, and Skis
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.