Keep this under your hat....

[Stig / Major Tom]

This could do damage to my reputation, so, " Mums the word!"
 Some of you are aware of my long time mower maintenance habits :
:
1) every fall think about  looking for the Stabil bottle.
2) as spring approaches think about looking at the spark plug
3) since most of the orig. 20" blade  is still there, move on to #4
4) check dipstick & top up from whatever oil bottle you can find (don't  use used scooter oil if possible)

My old Sears 20" mower started and ran just fine for 25 yrs, with the original plug, blade and oil until the 3rd wheel finally broke completely out of the chassis. (for its final year - it mowed just fine as a tricycle)

Sure hope I haven't messed up. Because today changed the oil on my 1yr old TroyBuilt with the Honda engine.
If word gets out....I can no longer mow while wearing my "Club Don'tfoolwidit If It Starts" T- Shirt .

Stig
*I'm pretty sure that half bottle of oil was OK. Carried it in my 1989 Jetta trunk for a couple of decades only.

[Stig / Major Tom]

For you nit-pickers....yes, every couple of years i would remember that it had an airfilter. I figure the added grass clippings in there would only enhance its filterin' capabilities.
And, lest you think i abused this engine - i always used premium gas!
Stig

[Clampett]

Air filter? Oh, you mean the mouse trap.

Now, if'n you hadda changed the oil and took care of it, jut think how long it woulda run!!!!!!

I'm having similar results with my riding mower. But it is a 3 blader and the original blades all cracked right down the middle 2nd year.
8 Years on the replacements but the deck is suffer'n a bit after I volunteered to cut the neighbors grass and they had an iron post cut off at grass level I didn't see.
Still cuts fine, but the deck rattles a bit 
So far (knock on wood) I'm still on the original belts, but they are lookin kinda frail.......

Now to you mention of not using scooter oil. If ya use some good TP and filter it, then I don't see why not!!!!

[EvilTessmacher]

I'm not wearing a hat...