why am i getting the mpg that i am????

[aj510]

picked up a 97 gtp, stock except a "hai" and flow master mufflers, i had to drive 3 hours to get it home and i got 29mpg which is what i was expecting and now that i have to home over the last couple of days its gotten worse little by little, i put in double platinum "oem standard" plugs, msd wires sea foamed the engine and am only seeing 14mpg. i do live in a city and there are a lot of street lights but should i not be getting closer to 17mpg? or am i just expecting too much of the car?

i havent manually calculated the mpg but will do so the next time i get gas

[matt5112]

must be your driving style if you managed 29 on the freeway.

Does it still get 29 on the freeway though?

[mechguy]

Your MPG can be almost anything in the world. My DIC currently shows 13.4 MPG, which is because the car spends more time idling than driving (in winter), among other reasons such as low temperature.

Check whether your other maintenance is good, such as filters, etc.

[tayl5645]

What theyre saying. This time of year is horrible for gas milage. Not to mention it depends on drive style if u mash the gas your gonna see crappy numbers. You wouldnt see these on the e-way cause your constantly at those speeds.

[aj510]

i did a good tune up so it should not be the parts, its got a new air filter plugs and wires. i havent had a chance to re check the highway mpg for improvment or not. the idleing comment catches my attenction tho becuase i am doing about the same. its maybe 1 mile to my job and there are about 5 stop lights in between.... if i do spend more time at lights would that make the guage show a lower mpg becuase im not driving far and doing more stand still?

[tayl5645]

That could effect it cause your DIC just does a calculation. Best bet is to calculate it yourself at the end of every tank. Ultimately you will be low in the winter with the cars being super cold. With that litle drive your car probably barely has a chance to heat up

[98GPGT2D]

if your only a mile from work, and have 5 stoplights in between, you can expect crappy fuel milage I would think. That doesnt give your car enough time to come out of "Open Loop". Open Loop means the car is running on preset values as far as air, fuel, and temperatures goes. Once the car is up to full operating temperature, it goes into Closed Loop, meaning it gathers all the information from the various sensors (IAT, O2's, MAP, coolant temp....) to make proper adjustments to the fuel mixture.

Seeing as how your only a mile from work, I can see that it would likely run Open Loop for 90% of your trip.


Jay

[BillBoost37]

Platinum isn't good in our cars overall. When you say OE replacement..do you mean Bosch? Those plugs get murdered quick in our engines and cause many running issues.

another thing is you seafoamed, this can sometimes kill an O2 or clog a cat in extreme cases.

If all else fails.. look at your right foot. I'd bet it's not helping.

[aj510]

I don't believe the seafoam caused any issues since it still runs gfeat and it didn't really smoke bad at all when I ran it through. Ill just have to manually calculate it I think to get a more accurate reading, I think the stop lights might be making it seem as tho I'm getting poorer mpg

[gtpinsc]

these cars like copper plugs. i personally run copper autolite 605's and get really good mileage with them. only downfall is changing them more often than plats or iridiums. but theyre cheap as hell so who cares.

[SlowNA06]

OEM standard is iridium now.
You may have a vac leak?

[cerick08GP]

Well, I’m just throwing this post out in hopes you don’t chase a ghost for the next few weeks. First off your car seems to be getting very average mpg for what it is. 29mpg hwy and 14mpg for your stoplight to stoplight commute is reasonable. Think about it, your car is about 14 years old and it is a little tired. Also, you bought a mid sized car with a supercharged V6, that is basically engine speak for V8.
Consider this alternative, save yourself the 23 cents in gas by walking to work.

[BillBoost37]

Evein driving in NYC my car gets better than 14mpg. I have trouble thinking it's old and stoplight driving is doing the 14mpg. But then when my car was built and I went on a smoke the tires from every light day..I still got 16mpg.