Terrible in-town MPG

[jrizz]

Highway miles still seem to be about right (22-28ish), but on the current tank of gas in-town is averaging around 9mpg. I've had the car a little over a year and for me it's never gotten the 17mpg indicated in the factory specs. More like 14mpg in-town. But now it's 9. Pretty bad. I'm not a speedster. Pretty gentle on the pedal. It's not my driving style.

Had some exhaust work done that I thought would improve fuel efficiency but it's really the pits right now. I don't know where to begin. Any thoughts?

 

[KZJonny]

It won't account for *that* level of fuel consumption, but I had luck with the broadly recommended Berrymans B-12 Chemtool or BG 44K fuel system cleaners. I saw better idle and slight improvements in fuel economy in my 2.5i and GT after a treatment and some italian tune up driving.

Might be a place to start and see where you land after cleaning up the fuel injectors a little?

Edited November 18, 2022 by KZJonny

[blackobxt]

Any exhaust leaks? Any way to pull a learning view? Have an access port?

[jrizz]

@blackobxtyeah i do think there is an exhaust leak, that's why i had recent work done, one muffler replaced. the shop said they thought they could get around having to do the other one, i think there was concern that the valve connecting the un-replaced muffler to the center pipe wasn't looking great. but yeah, there is some vapor and some detectable scent. thing is, mpg did get better after the recent exhaust work (July), but now clearly abysmal.

not sure what you mean by learning view...photos? nor access port. as you all can probably tell i'm not much a a mechanic. i'm not totally clueless but not far from it. familiar with working with my hands but more with wood. haven't been under the hood much and haven't even owned a car for many years.

[silverton]

excessively dirty air filter, dirty maf, sticky throttle body, worn spark plugs, fuel quality, dirty injectors, failing O2 sensors, knock sensors, and cats (or any exhaust restriction) can affect gas mileage

[ttnio]

winter blend gas.... terible

[BoozeRS05]

Without details it would be very hard for us to help you. Maintenance history ie any filters, parts and fluid changes, tune, tires/psi, fuel/oil being used, how many miles, 5mt or auto, etc.

There are good suggestions above, but it’s the blind leading the blind. Google the same question and you’ll get a better “how-to” guide

[jrizz]

@BoozeRS05I hear you. I'll try to follow up with those details later today or tomorrow with the hope someone will have some insight. I expect I'll have to take it to a shop eventually. I'm not opposed to rolling up my sleeves and doing work, if I have solid guidance, but in a lot of cases I don't have the tools. Anyway, all that to say that even if I take to a shop, I feel much better doing so with more knowledge, which is what I come here for. Thanks for your thoughts-

 

On a separate topic - anybody aware of a good phone holder? I got an iPhone 13 last year and the belkin holder for it which utilizes the air vent and it just will not stay up....too heavy and flops over all the time.

[blackobxt]

Without data it’s going to be just throwing crap at it and hoping something sticks. When you got your exhaust repair done did you reset the ecu?

another thing to do is to get a bottle of soapy water and spray all the exhaust manifold mating areas (where it bolts to the heads, the crossover flanges and the up pipe flange) with the engine cold and have someone start it for a few seconds and watch to see if you start to see bubbles forming. This will indicate a pre o2 sensor exhaust leak. Just to try and weed something out

[silverton]

I find it easy to use an aim'n'flame(bbq lighter) for checking exhaust leaks.  the flame wont stay lit with a leak.

You didn't mention what your mileage was, but if it's been at least 60k since you've done spark plugs, it's long over due and I recommend a major service!  the engine air filter is easy enough to check yourself, and a way to get fuel out of the equation is do a couple...maybe three tanks of premium and see what you get.

For what it's worth, my current tank with my 3.6 has been ALL city, I have a two mile commute and I let it warm up 10-15 minutes in the morning, and I'm getting about 11mpg using regular fuel, my next tank will be premium. My last two tanks with a solid driving mix using regular were 16 and 17mpg. I have found my carputer is consistently +1mpg over actual.

 

I love my CourseMS mount, but they don't make one for your generation

Edited November 18, 2022 by silverton