I just purchased a 2005 Trailblazer EXT I6. Before any modifications, I was getting around 14 MPG. I added a K&N Air Filter and a PowerAid Throttle Body Spacer. I was expecting to get an additional 1-2 MPG with these additions......
I have actually lost MPG! I am now getting 11-12 MPG..
I added a Lund Stainless Steel Grille insert as well. Would this restrict the air flow going into the engine bay, causing the bod gas milage? That is about the only thing I can come up with on why it is doing worse.......
Any thoughts or suggestions????
Thanks

Not a big fan of K&N. Lots of posts and experiences to be found indicating oil from filter coming in contact downstream on the MAF sensor. GM has bulletin out that if the MAF is coated with oil, they will not cover. Add to that, tests have shown the filter is not that efficient. See a complete filter test http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

There is more data that anyone needs.

As to Airaid- Mixed opinions if it works. I used to take the aircleaner of pops car, made a lot of noise, swore it was faster???

Let's keep in mind that the Spicer test in that link DOES NOT test air filters in a realistic manner--and the problem would affect K & N (oiled media) filters the most.

All the dust is dumped on them in an extremely short period of time. In real life, it builds up slowly, and THE DUST GETS OILED AND TRAPPED. K & N says that in very dusty conditions the filter should get additional application of oil because so much will have been soaked up by the dirt on the outside of the filter. Note that they DO NOT say the filter needs to be cleaned at this point--just add a touch of oil.

The biggest problem with K & N style filters is that they get cleaned TOO OFTEN. Put it in and LEAVE IT ALONE for a year. Inspect it but don't clean it until the dirt build-up is even with the mesh of the filter. Yeah, it will look terrible. The oiled dirt will actually IMPROVE the filtering ability.

If the INSIDE of your air cleaner isn't dusty, you aren't pulling in dirt. If it is, you need to seal up the openings, or find a different filter.

... I added a K&N Air Filter and a PowerAid Throttle Body Spacer. I was expecting to get an additional 1-2 MPG with these additions......

First off since you have the L6 (yes, it's officially "L" instead of "I"), take off the Throttle Body Spacer. Throttle Body Spacers give absolutely no benefit to our engines or any MPFI (multi-port fule-injected) engine.

11-12 MPG is horrible...for that fact even the 14 you were getting is horrible. I can normally get 17-18 and I don't exactly drive conservatively and it's typically 95-ish degrees down here.

My suggestion since you have an '05 and it's probably still under warranty is to put everything (yep, even the grille) back to stock, check your mileage for a month or so and see if it comes back. If it doesn't you've messed up your MAF sensor (or something else). If you keep getting 11-12 MPG with it in stock condition...take it to the dealer and tell them your mileage has gone down hill. If your mileage does come back, then start adding your mods back one-by-one giving a fair amount of time (a month??) between additions, so you can nail down which mod is doing it. When you find which mod is doing it...ebay it.

Unfortunately not all mods give "positive" results. Especially the TB spacer...they just waste your money and give you a nice whir/whistle that makes you think you're building HP.

baskerj,
I think if you will check again you will find that the 4.2L is in fact called a "I" engine.
gary

baskerj,
I think if you will check again you will find that the 4.2L is in fact called a "I" engine.
gary

No Gary, if *you* check again (and use official GM sources) the official engine type is an L6. Most people call it an "I6" incorrectly because its typically paraphrased as "inline". The "L" in "L6" stands for linear and is the official type of the engine. It is a 4.2L (this "L" is for litres) L6 (this "L" is for linear). I have plenty of GM documentation if you would like me to post it.

baskerj,
don't know what to say to you.If you want to keep calling it an "L" then that must work for you.
However I would be sure before I posted info on the web,that I know for sure what I say is correct.

However I would be sure before I posted info on the web,that I know for sure what I say is correct.
:disappoin
I completely agree with you, Gary, but you obviously don't practice what you preach. I call it an L6, because that's what it's called. It's not called an I6...and never has been. I guess in the end it doesn't matter...I just mentioned it in passing in my original post. However, since you felt the need to correct me (incorrectly I might add), I am merely trying to give everyone the correct information...isn't that what this forum is for...information? Dang...this is the first forum I've gotten corrected for being correct... :banghead:

Check it...this is a typically example of GM documentation:
http://www.gmtechlink.com/images/issues/arcv_pdf/1_01_e.pdf

Obviously I haven't read all of GM's documentation on the Vortec 4200, but all the documentation I have read, calls it an L6.

Would you be upset if you went to Autozone and asked for a 5/8 inch socket and they gave you a 16mm socket? The 16 is close...but not correct for your job.

It's all good man...I don't hold anything against you...but it may be better to ask questions than to correct someone. Maybe next time you can say, "Dude...what do you mean by L6...I've always called it an I6?" Just a suggestion...

Peace out. :smokin:

It's not a socket, it's an engine and I am sure if you went into your local Autozone and asked for sprkplugs for your 2003 6 cylinder, L or I, that you would get the right parts. That is providing the clerk has an IQ of over 75. Now back to the poor guys mileage problem.....

It's not a socket, it's an engine and I am sure if you went into your local Autozone and asked for sprkplugs for your 2003 6 cylinder, L or I, that you would get the right parts. That is providing the clerk has an IQ of over 75. Now back to the poor guys mileage problem.....

heh good point Stan...although I did go into an A/Z once and ask for plugs for my 2.8L V6 camaro...and the guy tried to give me 8 plugs. *laughs* I got a good chuckle over that one.

Regardless of engine or socket, we should try to use the correct terminology. I was a little ticked off that someone contradicted me without the correct info. If I'm wrong, I'll be the first to admit it.

As far as the mileage question, we've given a lot of suggestions, but haven't heard back from him. We can surely have a nice side-conversation while we're waiting or is that wrong too? ;) (just kidding)

Well, I guess that I am going to remove the parts 1 by 1 and see what is causing the problem. I also have 20" rims and tires. hopefully that isn't the problem. I have removed the Stainless Grille and will be checking the milage. I hope that this is all that it is. If the air flow is restricited coming into the engine (no matter if it is a I6 or L6 :iceslolan ), can that cause that much depletion on MPG? Thanks for all the help.

Well, I guess that I am going to remove the parts 1 by 1 and see what is causing the problem. I also have 20" rims and tires. hopefully that isn't the problem. I have removed the Stainless Grille and will be checking the milage. I hope that this is all that it is. If the air flow is restricited coming into the engine (no matter if it is a I6 or L6 :iceslolan ), can that cause that much depletion on MPG? Thanks for all the help.

No...I wouldn't think 20's would affect your mileage that much. I mean, we're talking 6 mpg less (or about 40%) than me. *IF* it's a mod doing it I'd be almost willing to bet it's either your filter or the TBS...and I'd lean towards the filter. But if I were you I'd remove the TBS first, because it absolutely does no benefit on an MPFI engine. Both are easy to remove. Can changes in air flow affect mileage? Sure it can. I'd take off all the mods and leave the wheels on....see if that fixes it. If it doesn't I'd head straight to the dealer and ask them to check it out...it could be a ton of things really. The last thing you want to have is detonation in your engine (rich - you engine is using more fuel than it needs). Detonation is horrible on engines. Good luck and keep us updated.

Ummm, theres no MAF in the I(or L)6 4.2L engine. There is an IAF sensor located about halfway up the intake, and it is basically a MAF, but it is different. There is a MAF right after the filter "box" on the V8s, but only on them.


Also, 11-12mpg is horrible. I think it is due to the newness of your engine, and will improve over time. I have an 02, and get 18 city and 21-22hwy. Towing my 4000lbs boat, I get 11-14mpg, depending on speed.

Mine is a EXT. I was assuming that they generally don't get as good as MPG as a reg. Trailblazer. 17-18 MPG would be fantastic! I would be happy just to get back up to the 14-15 range..... The TBS is a question for me. I hear in this post that it does nothing for the engine. I read in other posts how people swear by them and love it. I hope that the money spend on aftermarket parts would actually help, I am starting to wonder if it is all a waste of money now....

Mine is a EXT. I was assuming that they generally don't get as good as MPG as a reg. Trailblazer. 17-18 MPG would be fantastic! I would be happy just to get back up to the 14-15 range..... The TBS is a question for me. I hear in this post that it does nothing for the engine. I read in other posts how people swear by them and love it. I hope that the money spend on aftermarket parts would actually help, I am starting to wonder if it is all a waste of money now....

Having an EXT would definitely decrease your fuel efficiency...also if you have a 4WD as opposed to a 2WD. If you have both, I would expect in the 14-16 range...so 12 isn't too far from there...and it also depends on how you drive. Also, check your tire inflation....especially with those 20 inchers. Make sure it's up to spec (of the tire, not the door since you've modded those). If it's low, then you'll get a better ride, but worse mileage...if it's high you'll get better mileage but a bumpier ride.

Not to start another tangent, but I think it's important since gas prices are going through the roof. If you drive like Hank Hill and pretend there is an egg under the pedal, you'll get better mileage. Lately I've tried to slow down quite a ways before a stoplight...using less brakes and preferably not actually stop. A lot of fuel is used on start-up from a stop. Of course the ricers that are behind you get a little testie...but that's their problem. ;)

I have a 2005 LS TB 2w drive, with 2000 miles on it. Just took a 1500 mile round trip here in Texas and avg'ed 23.9 mpg with no/AC on first fill-up fairly level road 75mph . Hill country av'ed 21.6 with/AC 75 mph on second fill-up. In/around city av'ed 18.2. On return trip w/AC av'ed 20.9 mph. Going was from hi alt. to almost sea level. Used cruise control 99.9% of the time on the open road. Avg gas price $2.42/gal going $2.53 five days later coming back(same gas stations). I used 87 octane all the way tire pressure 30F 36R like the door panel says. I have been av/ing between 16 and 18 in stop and go city driving, no rabbit starts.

hey so did your mpg increase after you took the parts off or not?

Well, I took off the Lund Stainless Grille insert, and drove back to my home town (a 3 hr drive) and averaged about 18-19 mpg! Not bad compared to what i was getting. I am going to assume that the grill insert was blocking to much in-coming air and made the engine run very in-efficiently..... just a guess..... I am going to leave the 20's and the K&N filter on it for now, might take off the poweraid spacer and see if that improves it any more.....

I'm driving like I'm a grandma with grand kids in the back:) Less brakes means more mpg.

[QUOTE=spikeyhaired1]Well, I took off the Lund Stainless Grille insert, and drove back to my home town (a 3 hr drive) and averaged about 18-19 mpg! Not bad compared to what i was getting.[QUOTE]

You'll always get better mileage on long highway hauls...some that's kind of an apples to oranges comparison. For example, I get 17-18 driving my normal everyday route, but on a trip to Ohio, I got and average of 23. You may want to compare it with the more normal driving routes you did when you originally posted. Since it was a 3 hour drive, I'm assuming it was highway mileage and your problem hasn't really been corrected.