How much does missing oil sticker affect value?

Honestly, I wouldn't worry about it as long as there's evidence that it was there. If it bothers you, NOS stickers can be purchased and they even have a slight patina. 

Unless you plan to display it on it's side or upside down, I don't think anyone would notice.

I like original train boxes, but I like to see my trains better out of them.

I tell dealers I am not a box collector, but I all ways ask if they have the original box.

you actually answered your own question.  technically you shouldn't rate a car as a C7 condition if it has a missing or replaced/ repro piece.  the sticker may be a nice bonus to find, but i wouldn't call it an essential part of the car and i wouldn't expect to find one even if it wasn't mentioned as being missing in the description.  when i sell something i always include a picture of the underside and in buying it's nice to see that same shot, but not always a deal breaker for me.

'Value' is in the eye of the beholder.  A guy who wants to see real nice original standard gauge trains go around his track most likely won't care about the sticker.  I am in this camp.  If I pay, say $100 for a nice piece, I enjoy it till I'm drooling on my Wheaties, and sell it for $80 because it doesn't have the sticker, have I lost anything?  I think I have have gained.  Another point is, if a nice  90 year old piece is worth $100 now,  can't it be logical, (assumed - need the right word), that it will be worth more when it is 110 years old?  Your sense of 'value' seems to be a short term outlook.  I'm keeping my guys for twenty more years.  The 'value' is built in.

Of course there are different takes on personal value, but there is a constant value market (see the decades of Greenburg pubs), that fluctuates due to many factors. My question wasn't about personal taste, it was about the actual market and what labels might or might not do to prices. Just trying to get up to speed on a segment that is fairly new to me.

Greenberg pubs.  To me,'value' is what a piece is worth to me. For others, 'value' is what it can be sold for.   I wish you wouldn't have mentioned pubs.  I just got dangerously thirsty.  Cheers!

Dreyfuss, it really won't make any real/tangible difference except to the fussy collector if it is C8 or better.  And usually with cars that are less common.  What you have there is a nice, common (unless it is the orange/maroon with window celluloid) piece. 217 in that shape will hold its value if bought right.

Rob English posted:

Dreyfuss, it really won't make any real/tangible difference except to the fussy collector if it is C8 or better.  And usually with cars that are less common.  What you have there is a nice, common (unless it is the orange/maroon with window celluloid) piece. 217 in that shape will hold its value if bought right.

Thanks Rob.