The International Cessna 170 Association

As some know, I have a '56 172 with a Bolen tailwheel conversion. My recollection is that the oil dipstick for tricycle geared aircraft with Continental O-300 engines is different from conventional geared aircraft with the same engine. My O-300B dipstick is part # 539779. I have misplaced the part # for conventional aircraft dipsticks and wouldn't likely find one easily available. I leveled my plane with the level on the top of the battery box and the oil level shows 4 qts (excluding what amount is in the filter). When the tail is lowered to the ground the oil level shows 5 3/4 qts. Is there that much difference in the dipsticks? Since I ck the oil with the tail on the ground, is the volume MY dipstick shows reasonably accurate? Don't know how much shorter or longer the dipstick is that 170's have provided the correct one has been installed. I long ago marked my dipstick as I added each qt of oil, but this bugs me sometimes wondering what the 170 dipsticks would show. I suspect there are 170's that have had O-300's installed that were once on a trike and the same dipstick is being used as in my case, but just need to be sure I'm not running my sump too low.

Would it surprise you to hear that our 170 has a 172 dipstick. And long ago someone marked the dip stick with new lines and numbers. But there are so many lines now you have to remember which line is correct. Or more accurately thought to be correct. So when we check the dip stick and note there is 7 quarts, we also have to note if it is the upper 7 or lower 7 which is actually about 6.

In reality we've become use to pulling the stick and noting there is oil on it. Then if the level is about 4" to 5" on the stick and we're just making a Sunday breakfast run, we think nothing more of it and go fly. Why clutter our brain with what number it's at, there is plenty.

(From Steve Grewing a while back): Per Cessna Service Letter No. 170-1 dated 2-3-56, Subject: 170-172 Oil Dipsticks:
"The 172 dipstick is part number 539779 and painted orange.
The 170 dipstick is part number 531081 and is painted yellow.
On the 172 dipstick, part number 539779, the full mark, (8 quarts) is approximately the same location as (6 quarts) on the 170 dipstick, part number 531081."

Those old PNs have been superceded. The current PN for a 172 is 628413A1, and the current PN for a 170 is 628410A1. (the "A1" designation may be missing on the dipstick.)

Frank, you must be getting as forgetful as me.... You asked this question a few years ago: http://cessna170.org/forums/viewtopic.p ... rod#p14635

Using the wrong oil gauge rod (dipstick) can lead to incorrect servicing by over-filling or under-filling. Floatplane 170s should use a 172 rod.

Am I being over simplistic when I say that I put in 6 qts and my dipstick reads 6 quarts? I think I have the correct dipstick.

If you have an oil filter you will probably show closer to 5 quarts when you put in six.

This is the one that my airplane came to me with. I have no reason to suspect that it was ever changed.

http://cessna170.org/forums/download/fi ... &mode=view

Miles, that dip stick is NOT on the carpet at home ???. You must be a thrill seeker.

Thanks for the refresher. This confirms my thought that my dipstick is inaccurate as it is marked from the factory. I'll need to keep my oil level a bit higher going forward.
And yea, I must be getting forgetful Bob---err George

ghostflyer wrote:Miles, that dip stick is NOT on the carpet at home ???. You must be a thrill seeker.

No Ghostflyer, I’m smarter than that! .... it’s on a paper towel on the kitchen counter. And, it was 12+ years ago...

I met Frank at the airport today and we were able to answer some questions about the dipsticks.

My plane is powered by an O-300D from a 172. I retained my old dipstick from the C-145 from my 170, which is what I use, so I have one of each.

Part number 531081 is the C-145 Cessna 170 dipstick. Part number 628413 is the O-300 Cessna 172 dipstick.

A closer look shows that the 170 dipstick indicates 6 quarts at relatively the same level that the 172 dipstick shows 8 quarts.
As a side note, picture this:

I walk out to where my better half and two of her girlfriends are lounging by the pool.
I say, "I'm going over to the hangar to meet Frank."
Her: "Ok. What are you and Frank doing today?"
Me: "We are comparing our dipsticks."

That's when the jokes started..........

I will have to start calling it by it's proper name, the oil gauge rod. Although I'm not sure that will stop the ribbing I'm taking.