Catasstrophic converters and MPG???

[mrvette]

Wife has a 2012 GMC Acadia.....6 cyl/auto/loaded with crap......car looks new inside and out.....but the MPG sux only about 14 mpg......

will cutting out the cat conv. and replacing with pipe make less back pressure and therefore better economy,?? or what ELSE can be done to get that where it's supposed to be..??? which was supposedly about 19 mpg......and with just a 6 cyl engine it seems the thing should get an easy 25 around town even......

any suggestions??

[Rodnok1]

No cat removal won't help, just throw computer into fits...
Some of those got terrible mileage, is it awd?
Besides tune up, air filter etc... Go easy on the go fast pedal about all can do.
Neighbors had one and didn't get much better mileage than that.. They got rid of it.

[Bill]

Catalytic converter theft is epidemic in Houston. I wondered the same thing.....why not just fill the whole where your cat was before it was stolen with a test pipe. This obviously would create some difficulty for the car's computer, which now would have no input from the O2 sensors. Not sure how that would effect driveability.

But Gene's theory seems simple enough....a freer flowing exhaust, combined with a freer breathing intake, should not only get better mileage, but should get better performance, assuming the computer program takes those changes into account.

[Vette40th]

You can have the secondary O2s code deleted, so you can put free flowing exhaust or delete cats altogether.. You will never get a financial return on a tune if you did tune it out..
But, your vehicle doesnt make a lot of power, so it will be negligible.
Tune it up, keep tire pressure up to specs, and be kind on the throttle.

[MikeB]

Originally Posted by mrvette

Wife has a 2012 GMC Acadia.....6 cyl/auto/loaded with crap......car looks new inside and out.....but the MPG sux only about 14 mpg......

will cutting out the cat conv. and replacing with pipe make less back pressure and therefore better economy,?? or what ELSE can be done to get that where it's supposed to be..??? which was supposedly about 19 mpg......and with just a 6 cyl engine it seems the thing should get an easy 25 around town even......

any suggestions??

Moth balls.

New injection system (this should be right up your alley).
Other than that, I got nothing.

My V6 Bronco averages 18.1 mpg, and I don't lean on it.
Yet.

[Vette40th]

About the best you could really do is lighten it up.. New cars are heavy, and have little underpowered rpm engines pulling them.
My 4runner, as soon as I go over 2000rpm, the gas tank gauge takes a dive..
Its 5000 lbs with 270hp.. Joke

[Tikiman]

That's awful mileage. My wife's Yukon XL gets better mileage than that and it's got the 5.3L.

[09CTSV]

I'm pushing 400 HP on a V-6 and am heavy on the go fast peddle. Averaging 17.8 MPG with mostly city driving. I don't remember the GVWR on the Explorer but it is not light. Our conversion van, 3/4 ton with the 6.6, averages 14.3 MPG mainly city driving.

[Bill]

Question for everyone quoting mpg.....do you pen and paper calculate these numbers, or do you accept your car's calculation. I ask, because I've found over the years that the car's calculations are.....optimistic. With every truck I've had, and even the Cruze, I have found my actual mileage is always 1-3 mpg less than the trip computer advertises. Obviously the accuracy of one tank calculation is going to be off a bit due to how much gas you put in at a fill up, but over time, those differences average out and you get an idea of real world mpg v. trip computer calculated mpg.

[Vette40th]

I do the fill and calculate method. My 4runner(Limited 2019, all time 4wd) gets 17 MPG city.. 19 Highway on a good day below 75mph.

[Rodnok1]

I've checked mine a few times.. Spot on mpg showed by the puter.

[Frankie the Fink]

Originally Posted by bill_daniels

Question for everyone quoting mpg.....do you pen and paper calculate these numbers, or do you accept your car's calculation. I ask, because I've found over the years that the car's calculations are.....optimistic. With every truck I've had, and even the Cruze, I have found my actual mileage is always 1-3 mpg less than the trip computer advertises. Obviously the accuracy of one tank calculation is going to be off a bit due to how much gas you put in at a fill up, but over time, those differences average out and you get an idea of real world mpg v. trip computer calculated mpg.

There a ton of comparisons on the Honda forum vis a vis back of the napkin calculations vs onboard computer - the computer almost universally is 1-2 MPG optimistic for some reason.

The OP will not get a 5 MPG bump by breaking out the sawzall on the exhaust system and maybe make things worse.

[MikeB]

Originally Posted by bill_daniels

Question for everyone quoting mpg.....do you pen and paper calculate these numbers, or do you accept your car's calculation. I ask, because I've found over the years that the car's calculations are.....optimistic. With every truck I've had, and even the Cruze, I have found my actual mileage is always 1-3 mpg less than the trip computer advertises. Obviously the accuracy of one tank calculation is going to be off a bit due to how much gas you put in at a fill up, but over time, those differences average out and you get an idea of real world mpg v. trip computer calculated mpg.

Technology.
Wonderful.
Until the battery dies.

FUUUUUUUUUUUUUUUUUUUUUUUUUUU Technology.

[RMVette]

Wife drove a 2010 Enclave and we put almost 200K on it. Enclave, Acadia, Traverse and defunct Saturn Outlook all had the 3.6L engines. Gas mileage on our Enclave was reasonable when it was new but as it grew older the mileage decreased. When it was new I put a K&N filter in it (not a cold air intake but just the filter) and it helped on the mileage. Plus I ran fuel injector cleaner through it every 30K miles.

On those engines, keep the oil changed as frequently as you can or you face the dreaded timing chain death. I changed ours every 5K with Mobil 1 full synthetic and when I got rid of it, no timing chain issues. I read on the forums where people buy these with 100K on the clock and no knowledge of the maintenance history and wonder why they have to change the timing chains.

Good luck!

[Onebadcad]

I have removed all cats at time of purchase.
I have never gotten over 10 mpg with any car.
I have never gotten over 8K with any tires.
I have never owned a car the neighbors did not hate.
I have never owned a car for which the purchase price exceeded the modifications added.

I am a terrible person to get car advice from,,,
I am a terrible person,,,

[GTOguy]

As an automotive pro, I'll give you a pro tip: dump the Acadia while it still runs. These were one of GM's worst products when new, and now, at over ten years old, you are rolling the dice. That transmission and drivetrain is a ticking bomb. I am not kidding. Get rid of it.

[DJ_Critterus]

Gene, have you tried drilling holes in the exhaust?

[theandies]

What cutting the cat out going to do for gas mileage? Maybe get 2 or 3 more miles a gallon. Hahahaha.

[sublime1996525]

It's GM crap. I'd sell it before it explodes. I use Fuelly to track my mileage.

[Aerovette]

Larger diameter tires. One revolution gets you further down the road. More miles per gallon.