One of my regular customers brought his son into the shop the other day. It was right at opening time and good old dad made it a point to tell his son: "Gonzo probably hasn’t had his coffee yet, so go easy on the old guy."

He was right about the coffee, but that still didn’t prepare me for the story I was about to hear. The story started sometime earlier, apparently after I changed the fuel pump two years ago his gas mileage had dropped considerably. He was very upset and believed that I had done something done wrong to cause it.

He insisted I was to blame because he always tracked his mileage by way of his trip odometer. Before the new fuel pump, he would get close to 400 miles per tank. His accuracy was noted on his little logbook and showed how much gas he would refill his tank with. It was always around 23 gallons and never a drop more than 23 gallons. But now his tank was holding 26 gallons. His question, “So, where is the other three gallons going?” I had to laugh, I’ve changed a lot of fuel pumps, but I never have had anyone come in and tell me that it holds more fuel than before.

My guess was that his original gas tank sending unit was probably inaccurate and that was where his discrepancy was at.

“I’m pretty sure your gas tank hasn’t increased in volume since a fuel pump has been changed. I would imagine you’re probably mistaken as to how much your tank actually holds,” I told him as I reached for my coffee.

Nope, he wasn’t buying that answer. He knew how much his gas tank has always held and he knew I was the cause of his three missing gallons. What he wanted was for me to find out why his gas mileage has decreased so much.

I tried to explain it to him, but he was very, very sure he was correct and I wasn’t listening to what he was saying and he was getting quite loud and belligerent over the whole matter. Poor old dad just sat there with a smirk on his face. I kind of figured dad had already had enough of his boy’s attitude and figured old Gonzo was going to straighten him out. (This is going to take a lot more coffee.)

The aggravated son then began to tell me how he was a good mechanic. He had rebuilt a few motors in the past so he knew what he was doing under a hood.  (Note:  Putting parts together is like putting a puzzle together. There is a lot more to being a mechanic).

He was grasping at possible reasons why his gas mileage had dropped so much.  What gets me is how something as important as the involvement of the service light isn’t brought up into the conversation until after you have told me how good a tech you are and that you have already made the incompetent decision that I was to blame. (I’m going to need more coffee.)

So at this point, we have a service light on and we have a supposed loss of fuel economy (sort of). I’m sure there is more, there is always more,  so I had to ask, “Anything else?”

After dad and son dropped the truck off, I went straight to the glove box. I checked the owner’s manual as to how much capacity the fuel tank held. It had it in big bold letters: “26 gallon capacity,” not 23 as he was so sure of.

The next thing was to tackle the check engine light. Yes, there was a code. A code that might lower gas mileage, sort of, but not by three gallons. It was the EVAP solenoid valve code,  p0449. After doing the test on the valve, it turned out the valve wasn’t responding to the PCM commands.  A new EVAP solenoid valve solved the problem.

After all the phone calls were made and he arrived to pick up his truck, there was never any mention of the so called missing three gallons or the fact that it was merely the original fuel sender that was reading improperly all this time. Or the fact that the loose gas cap had nothing to do with the service light this time around.

I guess when you’re the customer, you don’t have to admit when you’re wrong, but you can be darn sure if the mechanic is wrong, everyone would know about it, and somebody would have to apologize.

Oh, and I apologize for being the mechanic in this story, and I guess I should apologies for one more thing … writing in BIG letters on his invoice: YOUR TANK HOLDS 26 GALLONS!