"Limpio mi manzanas"

I don't know if I can blame it on my parents, but I truly seldom sweat the small stuff - even before that became a favorite expression. Therefore, I realize my Spanish grammar is atrocious, but, I get by and yes, I realize it is alllll in the present tense BUT I have managed to get around Mexico for 34 years this way, so there.
But, I have brought tears to people's eyes with this TRUE story of when I first moved to San Miguel. I was at the Pemex station getting gas and it was the dusty time of the year here ( May) and so I needed my windows cleaned. I asked the "gas man" to "limpio mi manzanas" and I noticed he smiled and then to make matters worse I said front and back. He kindly did so (cleaned my windows) and as I drove off I looked in my rear vision mirror and he and his compadres had a big grin on their faces. Hmmm. I arrived at the friend's house that I was going to and immediately said to him, "the word for windows is ventanas isn't it?" and, when he answered in the affirmative, I related what I had just done. It has become a great story to tell...............You can bet I have never made that mistake again.