I have recently seen a fairly dramatic decrease in my MPG. I went from average of 15 to average of 13. This is doing the same daily drive, same driving habits, etc.

I recently changed my plugs, the air filter is clean, and the tires are properly inflated.

Any ideas where I should look next? At $4/gallon, every MPG counts!!! Thanks!!

 

Have you added any mods? Have you cleaned your throttle body? Are you going by the computer on your mpg, or are you doing the math on it?

 

Oops. Forgot to add that. The only mod I have made is I added a Aero super turbo exhaust. I also recently cleaned the throttle body.

 

Make that a Dynomax Super Turbo exhaust. Head in the clouds this morning!!

 

what plugs did you use?

 

And gap, also what engine?

Did you pull the TB off the truck? If so did you re-check all your hoses to make sure you do not have anything laying around unhooked.

 

It may be nothing. 2 mpg isn't a dramatic reduction, now if you came in and said -10 mpg then we would have a problem.

Are you going by the computer or are you doing the math?
What kind of gas are you putting in? (brand/octane)

Some gas stations might be switching to winterblend early and this will cause a small decrease in mpg's.

I wouldn't worry about 2 mpg's.

 

Thanks for all the replies.

I used the OEM Champion plugs, gapped to the recommended 0.045".

I cleaned the throttle body a few months ago. I did not see any drop (or increase) in MPG after cleaning it. I began seeing the drop before the plug change and it hasn't corrected since.

I thought of the winter mix also but I have never seen this low a MPG during any driving season, winter or summer, so I am attributing it to something else - unless they are really watering down the gas now that it is getting more expensive!!!

Sorry, I have a 2005 QC 4x4 with the 5.7, running 87 octane. I am using the computer for the MPG readings. I know it isn't accurate but I assume it's consistent so it gives me a baseline anyway.

You're right that 2 MPG isn't much but considering the 15 MPG I was getting, that is a 13% decrease, which is somewhat significant.

 

It is because you are using 10% ethanol blend crap. Mide did/does exactly the same thing with the 10% blend. Getting hard to find stuff now that is not blended.

 

Ditto here with my 02 1500 5.9L it is getting very hard to find the "good stuff."

Considering I only get 12-13 (hand calculated) in the city and 15-16 (ditto) hwy using the real thing...that drop to hig 10's low 11's and 13-14 sucks.

Oh well, that's what I get for driving a truck that can pull my house off its foundation.