New Exhaust = Worse Mileage?

About six weeks ago I got the frame replaced on my 2006 DCLB TRD Sport. I got them to install new exhaust while they were at it; basically everything except the headers.

I used to get 20 MPG, but now I am only getting 17 MPG. Seems like it is running rich.

A few factors that may come into play;
-Truck sat for two weeks while they worked on it (not sure how that would affect mpg though)
-I don't believe the new exhaust system was OEM (but it was an equivalent)
-Had to replace calipers as they would stick since didn't get used for two weeks
-In terms of accelerating, the truck feels a lot heavier
-Old exhaust system had a leak, it sounded like sh*t lol.
-I drive about 45 miles a day, 35 of which are hwy.

Given the price of fuel these days, it's bothering me that I spent $1400 on new system and got worse mileage out of it. I didn't expect it to be better, but I sure didn't expect it to be worse!

I'd love to hear thoughts from you guys.

Willy

 

I would do all the normal things, clean the maf sensor, replace air filter, change spark plugs. disconnecting the battery and allowing it to reset might also help adjust to the new settings it has to run in order to get fuel economy.
I havent heard anyone get worse mileage just from the exhaust, i would guess some other factor has crept up that either is affected by the exhaust, or something totally unrelated.
also i would check the brakes arent sticking like you said,you can tell by sometimes they will glaze over, that is the most obvious. but jacking up the truck and trying to spin the wheel is the easiest and often the most telling

 

More than likely it's a combination of things. For one, your battery would have been disconnected for a while so the truck has to relearn your driving habits and setting fuel trims, A/F mix, ect.. Second, depending on where you are in the country, winterized gas could play a small factor in the differences in fuel economy. You could run a bottle of that STP fuel system cleaner through a tank of gas to see if you get any difference in fuel economy. Given the age of the vehicle, your fuel injectors might be in the process of clogging up so a good cleaning could help out. Also, verify your tire pressure.

-J

 

Not sure what all related exhaust was replaced. Did this change out include a new Catalytic Converter?

 

Yes, the cats on both banks are brand new.

 

In my opinion there is no such thing as OEM equivalent when it comes to cats. I would find out exactly what you have and then start talking to the mfg. of the cats.

 

oh yes, the switch from winter gas just happened. that is definitly what it is.

 

I agree. OEM is built to Toyota’s specs by whomever is making the product. Anything else is made however that manufacturer wants. Still don’t need nderstand why people don’t get this.

 

Thanks guys, I appreciate your input.
For what it's worth, I am going to clean the MAF Sensor, Throttle Body and try the STP Injector Cleaner. I'll let you know how it works out for me. Also I will check the manufacturer of the exhaust and see if anything is apparent with their system vs OEM

 

Reset the computer ECU too.

 

Get a scan tool of some sort. I like the blue driver, then you can see what’s going on with your fuel trim numbers and o2 sensors. Are you getting any Check engine lights?

 

Not to worry - your truck needs to re-learn your driving habits because of the battery being disconnected (frame change). Wait a couple of weeks and recalculate. Your mileage will also be affected by outside air temperature. Depending where you are located this can and will be a factor.

 

My guess: several things come to mind. Colder temps now than a month ago and winter gas also just happened, (I lost 2mpg from one fill up to the next) and most likely battery was disconnected while they worked on your truck and the ECU needs to relearn your driving habits. As for the truck feeling heavy, I'd focus on brakes sticking. My parking brake would stick sometimes and it could definitely be felt. I suppose if I did not know it was the brake sticking that it would feel like the truck was heavy. Could definitely be the brakes since they just tore your truck apart and reassembled.

 

Well, I grabbed a bottle of that STP super concentrate injector cleaner, cleaned my MAF sensor with some CRC and while I was at it I cleaned the Throttle Body. It was gunked up pretty good but all clean now. Almost seemed like it couldn't quite close completely. I had to push it with my finger to get it to be 100% shut. I don't know if that would be normal or not? (First time I've opened up the intake system) Any how it'll take a week or so before I can see if it made a difference and recalculate mileage. I've got an 06 so the only way I can effectively determine my mileage is distance driven/fuel burned. Thanks again for the input and I'll let you know the results when I see them. Hopefully. Lol.

Willy

 

17 MPG is normal!!

 

Oh ya dude I lost a ton of MPGs. But damn it sounds good!

 

got to pay to play!!

 

Hey guys,

So about two weeks ago I cleaned the throttle body and MAF sensor and used a bottle of that STP Injector cleaner. My MPG is up to 18.5 from 17. I've read that winter gas can cause a decrease in mileage by 10-20% so that's probably the culprit here. I never really noticed in previous years about my decrease in mileage during the winter time so unfortunately I can't say for certain it is the winter fuel but so far that's what it is looking like. Especially since the switch to winter fuel is done mid September, about 3 weeks before I got my frame/exhaust replaced. I guess I will have to wait until May when they switch back to summer fuel to see if my mileage increases then.

Willy

 

Maybe, your frame was so rusted that it weighed a lot less and now since they replaced it it weighs a lot more. /s

 

*great