Interesting gas mileage results

[Iplayfarmer]

I nearly always check my gas mileage when I fill up with gas. I drive a '99 Chevy Half Ton 4X4 with an extended cab and long bed. I typically get just under 16 MPG empty and 9 to 11 MPG when pulling a trailer.

This past weekend I delivered a horse to West Yellowstone Montana. I was late getting out of town (Thanks, Dear), and so I was pushing the truck as much as I dared. The trip included pulling the infamous Ashton Hill which is known for being steep and long. It also included some gravel roads.

I filled my tank yesterday, fully expecting to be on the low end of my usual 9-11 MPG, but to my surprise I got 13.5 MPG. Maybe I should drive it like I stole it more often.

 

[Diamondpilot]

I am wondering if you either got less than full when filling back up for some reason???? Or if the pump you used was uncalibrated giving you more fuel than shown on the counter.

One other possibility is my uncle is messing with you. He had a guy that worked for him when the first Hondas came over. The guy bragged on that car so much so my uncle would add a gallon or so to the gas tank when the guy was not looking. It only had a 10 gallon tank or so and that gallon would make him think he as getting 50 mpg. The next week he would siphon out a gallon or so, back then you could still do that to cars. He would then think his car had dropped to the low 20's. He also put ATF, Oil, and Coolant in some oil cans and would squirt a puddle of one each week or so. He had that car back to the dealer dozens of times while my uncle just laughed inside.

He did the same exact thing with the fluids to a neighbor who had a JD tractor and bragged it up and down.

Chris

 

[dodge man]

Sometime it doesn't take much of a change to make a difference. Maybe it was cool and you were using the AC less. Maybe its often windy, and this was a calm day. Sometimes just driving a little slower can make a huge difference.

 

[Iplayfarmer]

I am wondering if you either got less than full when filling back up for some reason???? Or if the pump you used was uncalibrated giving you more fuel than shown on the counter.

One other possibility is my uncle is messing with you. He had a guy that worked for him when the first Hondas came over. The guy bragged on that car so much so my uncle would add a gallon or so to the gas tank when the guy was not looking. It only had a 10 gallon tank or so and that gallon would make him think he as getting 50 mpg. The next week he would siphon out a gallon or so, back then you could still do that to cars. He would then think his car had dropped to the low 20's. He also put ATF, Oil, and Coolant in some oil cans and would squirt a puddle of one each week or so. He had that car back to the dealer dozens of times while my uncle just laughed inside.

He did the same exact thing with the fluids to a neighbor who had a JD tractor and bragged it up and down.

Chris

I thought about the calibration or underfill option. There are two gas stations I normally fill up at... one near home, one near work. I filled up at the one near home on the way out, and I filled up at the one near work after I got back. Usually I get pretty consistent results between these two gas stations. If it is a calibration issue, it's a new occurance.

Your story about your uncle is great. I'm now on the lookout for someone I can do this to. I won't be able to siphon gas out of these newer cars, but I can still play with someone's head. I once calculated my mileage at 24 MPG or some crazy high number like that for a truck. It took me a full day to figure out my Dad must have put 5 gallons or so in the truck when he had borrowed it a few weeks before.

Sometime it doesn't take much of a change to make a difference. Maybe it was cool and you were using the AC less. Maybe its often windy, and this was a calm day. Sometimes just driving a little slower can make a huge difference.

I'm well aware of the difference that driving and road conditions can have on fuel economy. That's why I was so surprised. I was in a hurry and driving hard on this trip... Fast starts, hard braking, and pulling hills. If anything, I should have gotten worse gas mileage. I'm sure there's some valid reason for it. The only thing I can think of right now is that I made up for the hard driving on the way up by driving easy downhill all the way back. In hindsight it would have been interesting to fill up in West Yellowstone to see how my MPG differed on the way up vs. the way back. But, have you ever priced gas in West Yellowstone?

 

[JakeBrake]

I get about the same mileage towing with my 95 GMC K1500 350 cu. in. 4x4. however, I would be thrilled to get 16 MPG unloaded. My best mileage unloaded is about 14 MPG.

A more accurate way to check your gas mileage is to keep track of all gas added for at least 1,000 miles. My experience is that if I get great mileage at one fill-up, I will get terrible gas mileage at the next fill-up. This is due to the differences in the automatic cut-off from one pump tp the next. I suppose you could add gas until gas runs out the fill port, but even that could vary based on how level your truck is at the time.

 

[Iplayfarmer]

I get about the same mileage towing with my 95 GMC K1500 350 cu. in. 4x4. however, I would be thrilled to get 16 MPG unloaded. My best mileage unloaded is about 14 MPG.

A more accurate way to check your gas mileage is to keep track of all gas added for at least 1,000 miles. My experience is that if I get great mileage at one fill-up, I will get terrible gas mileage at the next fill-up. This is due to the differences in the automatic cut-off from one pump tp the next. I suppose you could add gas until gas runs out the fill port, but even that could vary based on how level your truck is at the time.

I check every time I fill up and then keep a mental average. It's probably not as good as an actual 1,000 mile average, but it does for my purposes.

I just thought of something. When I filled up before the trip I had the trailer on. I had the truck alone when I filled up after. I wonder if that may have had something to do with it. Good old half ton Chevy squats like a dog when it's loaded. That could have had something to do with it. My mileage was a little low on that fill up, but I had been pulling a trailer off and on for a lot of that tank anyway.

I may never know what really happened.

 

[Diamondpilot]

I think that was it. The trailer can make a real difference because of the angle of the tank and the vent system. It could have had a air pocket in it.

Chris

 

[davkir]

That's a good point. I had an 06 Mustang that you could never tell if the tank was completely full.

 

[DAY]

The Mythbuster guys did several tests relating to mileage. In one they drove with the tailgate up/down, another windows open/AC running. One test was open road, LA-Vegas, the other around a track at constant speed. MPG didn't differ enough to matter.

Except for that last sentence, I probably have all the details wrong. . .:laughing:

 

[Iplayfarmer]

The Mythbuster guys did several tests relating to mileage. In one they drove with the tailgate up/down, another windows open/AC running. One test was open road, LA-Vegas, the other around a track at constant speed. MPG didn't differ enough to matter.

Except for that last sentence, I probably have all the details wrong. . .:laughing:

I remember the "No Left Turns" episode. Truck stalled going down Lombardi Street because the gas all ran away from the tube in the fuel cell they were using.