New Borla, Bad Gas MPG

1sand2s

Member
Joined
Dec 17, 2022
Messages
31
Reaction score
41
Location
Round Rock
I installed a new catback borla system last week (140914). The thing sounds great. I love it, but ever since I fired it up I noticed the mpg dropped significantly. Before the exhaust, the computer showed about 13 mpg. Not great, but whatever. Afterwards it is showing 8.7 mpg and the number keeps dropping the more I drive.

When I slightly press the pedal and get the rpm to 1400, the readout shows 2 mpg. I don't remember it ever showing it that low before. I don't drive this thing hard at all. It has 1600 miles and I'm babying it.

Anyone seen this? Any ideas?
 
Did you by chance add a cold air intake also? I haven't heard of the exhaust causing this, but I have seen a few posts on Facebook about different intakes causing people to get worse MPG. Basically people complaining that they didn't notice any change other then a drop in MPG.
 
Did you by chance add a cold air intake also? I haven't heard of the exhaust causing this, but I have seen a few posts on Facebook about different intakes causing people to get worse MPG. Basically people complaining that they didn't notice any change other then a drop in MPG.
No. I would expect with more air going in, the fuel consumption would go up, but I haven't installed that yet.
 
No. I would expect with more air going in, the fuel consumption would go up, but I haven't installed that yet.
Odd, not sure. I have a Borla crate muffler on mine. Lifetime average is 15mpg. That's with some towing and a good amount of idling. I can get 17-18mpg pretty easily with mixed driving. Not sure on stock though as I changed the muffler the day after I got the truck lol... 8 MPG diffenitly doesn't sound right though.
 
Did you mess with the o2 sensor when installing the exhaust? If so, you may have damaged it
or touched the sensor end that would make it read the o2 and cause the computer to run the engine extremly rich.
 
The fact that you were only getting 13 mpg on a stock truck seems wrong, and usually the only reason that exhaust has any effect on negative mpg is because it sounds better and you are getting on it more. You haven't changed fueling at all so something else is wrong.
 
Your gas mileage will drop after any mod that alters MAF signal or back pressure.

A few tanks of gas and the fuel maps will relearn. Par the course.
 
  • Like
Reactions: AXE
Thanks for the input. Seems to have leveled out somehow. Maybe it needed time, but mpg seems to be back to normal. The thing sounds awesome. Wakes up the neighborhood and gets everyone's attention when you mash the gas. This truck is a beast. Go get one!
 
Exhaust alone doesn't typically make your MPGs worse. Giving it more throttle to hear that new exhaust certainly does though.

Make sure you're not giving it a little more gas to take advantage of the improved sound. ;)
 

Most Member Reactions

Back
Top