MPG Drop

[Jakegday]

no codes, besides the 420 one for not having a cat.....

[2k6GT]

Man i'm getting 22 on hwy at 70 mph this sucks

[Liquifire]

yeah........you should be getting better than 22 on the highway.......I would clean your MAF with the correct cleaner, do a seafoam cleaning through your gas and your brake booster line and see if that helps........how old are the plugs and are they the correct type?

[Jakegday]

i had 250 highway miles, i just filled up and checked it last night, 23mpg. DAMN! im thinking it might have something to do with my front end though..... i had an alignment done last month and its pulling to the left again already

[Liquifire]

a front end alignment may affect it, but not that much. I can get atleast 350 highway out of my tank.......and I have a GTP......something is off....

[03GTPLE]

So are you saying my 23 MPG with cruise control on the whole time (on the highway of course) and 330 mile range is not where I should be for a bone stock 03 GTP with 60000 miles? I was gonna change out the fuel filter...but it won't stop raining.....

-Jesse

[Liquifire]

So are you saying my 23 MPG with cruise control on the whole time (on the highway of course) and 330 mile range is not where I should be for a bone stock 03 GTP with 60000 miles? I was gonna change out the fuel filter...but it won't stop raining.....

-Jesse

this is sounding pretty close to OK I guess........depends on what area you live in too........it is not really hilly around here....Have you ever changed your plugs out on the gp?

[03GTPLE]

I just picked up the car, and haven't changed the plugs. I live in Colorado, and drive 60 miles on the interstate each way to work...everyday... so I'm filling up every 3 days. (fun) Hmm, I haven't even checked the plugs to see what shape they are in. I'll check at least one of the front three when it stops raining.....argh.....

THANKS!

[Liquifire]

these are not supposed to have the standard platinum plugs due to us being supercharged. You may just need a simple tune up......how is your air filter,etc? Your MPG's arent terrible but they arent quite what they could be.......is it hilly/mountainous around you on your trips?

[Liquifire]

There was a gas mileage thread and some people were getting 30+ MPGs on their grand prix's on the freeway. I dont get that good......

[03GTPLE]

these are not supposed to have the standard platinum plugs due to us being supercharged. You may just need a simple tune up......

Well, that may do it. I guess I was assuming that they'd be the standard 100k platinum plugs....kinda like I assumed that there would be child security locks on my rear doors...stupid GM.....

how is your air filter,etc? Your MPG's arent terrible but they arent quite what they could be.......is it hilly/mountainous around you on your trips?

Air filter is a freshly recleaned and oiled used K&N drop in. All fluids are clean, cv axles look good. I figure it's time for the fuel filter to be changed, but that's all I was thinkin as far as regular maintenance...I'll look at the plug once the rain stops while I'm home....maybe this weekend.

I wouldn't say hilly/mountainous like you are probably thinkin that I'm doin switchbacks and all that every 5 minutes. It's relatively flat, probably no more than anywhere else in the country (and yes, I've been there).

[2k6GT]

yeah........you should be getting better than 22 on the highway.......I would clean your MAF with the correct cleaner, do a seafoam cleaning through your gas and your brake booster line and see if that helps........how old are the plugs and are they the correct type?

What cleaner for the MAF?? okay i've heard of seafoam cleaning ... just dump it in a full tank of gas? brake booster with seafoam?? pugs need to be replaced...

[Liquifire]

they make specific MAF cleaner at your local auto parts store. Yes the seafoam will explain how to mix with gas and oil on the seafoam can. If you are doing the intake manifold, you take one third of a can and have the car suck it in through the brake booster vacuum line and let it soak in there for a while and then start it back up after fifteen minutes or so. It cleans everything out in there.........If you are going to do this there is more detailed instructions on other threads on here or videos of it on youtube........You do not mix this with the brake fluid......... I am not sure but I believe the original stock plugs are iridium which last a lot longer than copper(but some believe not perform as well) but not as long as platinum. I think iridium is rated for 50k but I dont know if they should really be in there that long or not( I wouldnt leave any plug in as long as rated) but the copper should only be ran for 10k max........but they are cheap.

[2k6GT]

You like copper or plat? plugs that is....

[Liquifire]

if you have a gtp you should not run platinum..........either copper or iridium. I bought coppers for now because they are cheaper and I plan on dropping to the 3.4 setup and I will have to find out which heat range I can run before trying the iridium. If I had a gt, I would run platinum......