Back in my trucking days I had a good friend who was a lead mechanic at the local Kenworth shop. He would tune up my engine so I could out pull guys with bigger engines.
One day this dude comes in with a 600 cummins complaining that I had out pulled him with my 444 cummins. "It's not smoking" he said. "Not getting enough fuel".
I was standing beside Terry (the mechanic) when he said this. We looked at each other and smiled. The guy left so we did a quick check of his fuel pump pressure.
"Well its at a stock setting" said Terry and I don't want to turn it up as the guy is a driver and does not own it. "What shall we do?" I said. "Here you drop one tube of grease down that stack and I'll put one down the other"
So we did. A week later the guy came back and Terry asked him how it was now. "Oh it's pulling better now and smoking really good" We never did have the heart to tell the guy.
We had some pretty good chuckles over that one with a few beers later.