Mileage dropped off pretty bad lately....

[sootie007]

Mileage has been dropping off over the last 2 months pretty bad lately -2.0 mpg in my 3.7 lib with 109k miles....weird thing is truck wasnt idling bad etc ?

Just for the heck of it I put 16 oz of Marvel Mystery oil in my full gas tank ......ran it through ...filled up and this week on a full tank of gas I got near my all time best high avg at 18.1 mpg...so it did something ? Cleaned plugs / chambers ??????? I cant argue with success - it worked for me .... (dunno) J

 

[rockymountain]

the mileage doesn't coincide with the unusual cold whether you are having does it? I get 2 MPG less in the winter up here in Indiana. What was the temp while you had bad mileage vs. good?

 

[S1Loki]

I noticed an increase in mileage this past week. Gained over 2mpg with the ambient temp increase. So this is something others have noticed.

 

[kj924]

You could have a caliper starting to stick....or an e brake dragging. Jack it up and check the tires for easy rotation. Start with the simple stuff first, then it's a process of elimination.

 

[AlexKJ]

You could have a caliper starting to stick....or an e brake dragging. Jack it up and check the tires for easy rotation. Start with the simple stuff first, then it's a process of elimination.

Will you notice something if one of the wheel bearings is going south?

 

[moparman]

Winter blend gas, especially with 10% ethanol will make mpg go down.

 

[Dave]

Winter blend gas, especially with 10% ethanol will make mpg go down.

Do they use winter blend gas in Florida?

Dave

 

[tjkj2002]

10% ethanol will make mpg go down.

I get better mpg's on 10%-15% Ethanol premium gas then non-Ethanol gas.

 

[TigerClaws]

Dont know about ethanol, but no matter what, it is pretty simple, cold air = more air for same amount of cubic feet as it compresses. More air makes ECU shoot more gas to keep same ratio fuel/air to the pistons ... So yes it HAS to lower mpg in cold temp. If i take my dirtbike down to sea level say at Quebec City, ill have to clip up the needle in the carburetor because it wont run sweet since im at 1400 feet altitude over sea level and air isnt at the same pression (barometric i think ?) Im no meteorologist but i know that

 

[Dave]

I get better mpg's on 10%-15% Ethanol premium gas then non-Ethanol gas.

Well, look at your altitude in Colorado.

 

[tjkj2002]

Well, look at your altitude in Colorado.

I get even better mpg's when back in South Dakota(east side of the state) with 93 octane premium with 15% Ethanol,3000' elevation there,guess my KJ has the taste for the good stuff.

 

[blue_kjR417]

You could have a caliper starting to stick....or an e brake dragging. Jack it up and check the tires for easy rotation. Start with the simple stuff first, then it's a process of elimination.

how freely should they spin?

 

[kj924]

Will you notice something if one of the wheel bearings is going south?

I think the bearing would have to be pretty bad before it would have that great of effect...but all wear is slowly leading to lower mileage.

how freely should they spin?

You should be able to spin the front tires by hand without much effort. Jack the front up and give them a spin...repeat at the rears.

Basically, just make sure there isn't a tire dragging causing rolling resistance. Step 1 Eliminate drive train problems....then go on from there...tire pressures...and so on.

I actually found all 4 tires down on press. on my rig last week, my mileage was down because of this. I'm not saying this is the problem, but eliminate things that's not going to cost money first.

 

[sootie007]

Yes its been REALLY cold down here in fl. so maybe that had more to do with it than I thought...J

 

[Dave]

I actually found all 4 tires down on press. on my rig last week, my mileage was down because of this. I'm not saying this is the problem, but eliminate things that's not going to cost money first.

Yeah, me too. It's the cold weather.

Dave

 

[kj924]

Yeah, me too. It's the cold weather.

Dave

Haha they were anywhere between 27-34 Psi...not really good for mileage on these 31's

 

[TigerClaws]

Yeah forgot air in tires also compresses ... if you were border line then you became underflated ... Just watch your air when it gets back to hot temperature if you added some youll become overflated

 

[sootie007]

2nd tank after Marvel and she was way up on mileage again...I think it was cabon buildup POSSIBLY ...will keep all advised ....my gut says the stuff worked..... J

 

[kj924]

2nd tank after Marvel and she was way up on mileage again...I think it was cabon buildup POSSIBLY ...will keep all advised ....my gut says the stuff worked..... J

Marvel? What's that?

 

[autoboy454]

MMO, Marvel Mystery Oil