Large Drop in Gas Mileage After Sitting

[Alfa]

Driving around town I have normally gotten 16-17 mpg, with 15.5 being the lowest on regular gas.. I went out of town and the Bronco sat for 3 weeks in the Texas heat. Since I have returned I am now getting around 12 mpg. Same driving style. I also don't remember hearing the engine fans going full blast at idle, but then it is super hot right now.

I thought it got a little better driving in sport mode aggressively for about 10 minutes (thinking it might clean out the injectors), but that was just wishful thinking.

Has anybody experienced anything like this?

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[Silver-Bolt]

Hand check the mileage do not rely on the computer for the actual mileage.

 

[Alfa]

Hand check the mileage do not rely on the computer for the actual mileage.

I thought the same thing, so I filled back up on half a tank. Came out to be 12.35 mpg

 

[JT58Bronc]

Nope, sometimes I let my Bronco sit for 2 weeks or more in a storage unit of at home in the garage and no such problem. We don't drive it much, only on weekends. Always get over 22 MPG.

 

[userdude]

You might check your tire pressure, which can diminish gas mileage by several miles per hour when underinflated. I always drive 38-40psi around town, which is bumpier but also better gas mileage.

Mine also sits garaged (in Texas) for 2-3 weeks at a time nowadays and I haven't noticed any diminished mileage. This includes sitting for mostly three weeks in a garage, then a roundtrip to Amma-rillah! last weekend. Got 19mpg roundtrip (outside of Merus).

 

[Alfa]

You might check your tire pressure, which can diminish gas mileage by several miles per hour when underinflated. I always drive 38-40psi around town, which is bumpier but also better gas mileage.

Mine also sits garaged (in Texas) for 2-3 weeks at a time nowadays and I haven't noticed any diminished mileage. This includes sitting for mostly three weeks in a garage, then a roundtrip to Amma-rillah! last weekend. Got 19mpg roundtrip (outside of Merus).

I haven't actually put a air gauge on them, but he truck is reporting 40 psi for each tire.

 

[userdude]

I haven't actually put a air gauge on them, but he truck is reporting 40 psi for each tire.

I haven't found mine to be terribly off (although not instant when airing up). Another possibility is bad gas; I got some bad gas in Austin a few years ago in my Chevy near midtown. I could feel that, though, maybe not it if your ride is smooth. Gas can also settle contaminants when left idle; that used to happen with my older Chevy, and I eventually had to pull the tank and clean it and replace the fuel pump.

Someone else may have some other good ideas. I would probably say if it keeps up, take it in for service.

 

[Alfa]

maybe bad gas. I filled up when I got back with regular unleaded. Burned about half a tank, just filled back up with premium to see if that made a difference. Hasn't yet, but thinking about it, I did go back to the same Exxon station. I think I am just going to have to let this run down and try getting gas at a different station.

Maybe I will make a Lockhard BBQ run tomorrow to burn off the gas "for science". ha!

 

[userdude]

maybe bad gas. I filled up when I got back with regular unleaded. Burned about half a tank, just filled back up with premium to see if that made a difference. Hasn't yet, but thinking about it, I did go back to the same Exxon station. I think I am just going to have to let this run down and try getting gas at a different station.

Maybe I will make a Lockhard BBQ run tomorrow to burn off the gas "for science". ha!

Nice! lol One of these days I'd like to try Snows, but it's a long drive from here.

 

[Alfa]

Nice! lol One of these days I'd like to try Snows, but it's a long drive from here.

I would like to try them too, but hard to get motivated to drive an hour to go stand in line, specially early on a Saturday morning.

 

[Phil Brown]

I know that my Dads old truck used to get bad milage after he would let it sit, but me and my brothers had mini bikes that needed gas and we had a hose but no $

 

[Alfa]

When I got back I still had about a 1/4 tank. I drove it some, then filled up. I didn't know anything wrong until I reset the gas mileage after filling up. So not 100% sure if it was the sitting, or the new tank of gas. I will rule out the gas by getting rid of it.

At 12 mpg, it won't take long to make it disappear.

 

[Alfa]

So the engine fan blasting at idle normal in this heat?

 

[BAUS67]

So the engine fan blasting at idle normal in this heat?

Especially if your a/c is on.

 

[MayhemMike]

Someone siphoned out some of your fuel while it sat and you were away. Lol.

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