Today I went to visit the wife and kids who are staying with her parents (~90 miles away) while her mom undergoes chemotherapy. Since I tracked my last trip there and got 18.453MPG with the A/C on, I decided to see what I would get with A/C off. I had driven 20 something miles since I had last filled, so I topped off before I left and put in a gallon and change.

I got back into town this evening, and went to a different Phillips 66 station down the road from where I had filled before the trip (because they have 92 octane instead of 91 octane). I began fueling, locked the nozzle and began to clean the 100s of bugs from my windshield. Before 1/2 of the windshield was sorta clean, the pump clicked off at 3.x gallons. Knowing I was a tick above 1/2 tank, I cussed the machine, and clicked it on again. Seconds later, it clicked off. From there on, I turned on the ignition to see the fuel gauge and filled it until the gauge read full. I had to over-ride the pump about 4 times to get the gauge to full.

In the end, the gauge was a tick over the full position (where it usually reads when filling the tank in the past) and I had put in 9.026 gallons.

Calculating miles driven (trip odometer) divided by gallons to refill comes to 21.216MPG.

Two questions:
Does the A/C really have that much of an impact?

Do I need to start worrying about something wrong with my fuel tank causing the station pump to shut off early, since nobody else had had a problem according to the people working at the station?

 

There is nothing wrong with your tank. Both my D1 and D2 do it at a Shell up the street from my house. I go to the Citgo at the other end of town and they both fill up fine. Its touch and go. It may have to do with the force that the gas is going in and if the vent in the tank can compensate.

A/C does put a strain on the system. But if your getting those numbers with it on, i would be really really happy. Or check your math again....

 

As we say at the dealer
Customer vehicle is working to manufacturer's specifications. No Fault Found.
Its Fine.

As far as AC causing an impact, it can cause a huge impact. Something like 15% fuel savings

 

If you really want to see how much of a impact your a/c has on MPG do the trip with the windows down and see what your MPG is.

 

Some vehicles with pump in tank (like Rovers) - if running while fueling, fuel pump or return line can fool the gas pump. Had another SUV that would do that, learned to turn off the ignition (they tell you to do that anyway, some don't).

Don't believe you high number will repeat, unless it is down hill all the way.

 

I really don't think my vehicle has any problems with the fuel system causing the station pump to shut off early, because this is the first time, but I will find out in another 150 miles or so (1/2 tank in town driving).

I am seriously shooting for that elusive 22MPG.

 

How in the world are you getting 21MPG? 50 on a constantly level highway and shutting it off down hills when you get to them? Seriously, I'm just wondering if you are calculating this correctly!

 

^^ agreed...^^^ How??

 

Its easy to do guys. I got 24mpg once.
Use the cruise, keep it under 70mph, windows up, premium gas, tires at 40psi, good tune up, no roof rack, front airdam in place...it cam be done.

 

I did not use cruise on this trip, and rarely do. My thoughts on that: if driving across Kansas, or some other flat state, I would use cruise control because it would be more efficient than my right foot. However, this trip to the in-laws involves lots of hills, both small, and large and long (a few steep and long enough to give an extra right lane to slower vehicles *me* ). If the speed limit is 60 and it is flat, I do 60. On downhills I might get up to 65. Climbing the long hills, my ankle doesn't pivot much. 60..55..50..all in the slower traffic lane so people can pass in the left lane. I NEVER use my brakes on the interstate, except to avoid an accident. On this highway, there are several towns that the speed limit is reduced from 60-65MPH to 50, 45, 30MPH. I just ease my right foot well in advance, and do not need to brake.

I can't wait to drive there again this weekend, and hopefully have the station pumps working properly, to see if this last trip with the HVAC on "econ" can be duplicated, or bettered.