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06 KJ Sport · **Posted:** Sun Jan 20, 2008 1:11 am

Here goes the next series of MPG questions. #1 For everybody that is running a aftermarket air intake what was your MPG before and after the mod? #2 For everybody that is running a aftermarket exhaust system what was your MPG before and after the mod.

What I am looking for is, for the 1 step back I am looking for the 2 steps forward.

Jeepjeepster · **Posted:** Sun Jan 20, 2008 3:05 pm

I replaced the stock exhaust with a flowmaster and the difference is not measurable. I cut all the connectors out and just replaced it with a piece of 2.5in pipe.

Also have a drop in K&N filter, difference in not really measurable.

With that said, I also have a lift and 30" tires but my mpg is decent. 16-17 average.

RAYMAN975 · **Posted:** Mon Jan 21, 2008 8:38 pm

i have an AEM brute force intake with a K&N filter. stock exhaust. and checked milage at half a tank of gas, i was getting 13.7 with 90% highway driving this past weekend. it doesnt help that it was about 10* outside, i guess cold air really is more dense

i have a coleman roof basket, roof lights and 245-70 Grabber AT2's as well

dloc_jeep_KJ · **Posted:** Mon Jan 21, 2008 9:35 pm

i dont think either of these mods will pay for themselves by money saved at the pump. on the oher had they will help some what on performance. if ur air filter is just cloged up and old u could see some improvements though. checking ur tires air pressure can also help some w/ gas mileage. the larger tires, lift, and a roof basket w/high lift have hurt my gas mileage the most.

2006 KJ · **Posted:** Mon Jan 21, 2008 10:05 pm

before K&N cold air and flowmaster 40 18mpg.. 21-22mpg ( with a 6 speed )

Jeepjeepster · **Posted:** Mon Jan 21, 2008 10:11 pm

Yea, it was around 8F the other day and I got around 14mpg. It warmed up to 20F and it went up to 18mpg. For some reason these engines dont like really cold temps.

Never had this problem in other cars.

RAYMAN975 · **Posted:** Mon Jan 21, 2008 10:29 pm

glad im not the only one. wind chills here were like -12F. i couldnt believe it when i calculated the MPG, 13.7 highway!!! with cruise on the whole time at about 65mph cant wait to see my MPG's when summer comes around

DarbyWalters · **Posted:** Tue Jan 22, 2008 8:41 am

If ya'll are at temps like that you should think of a cheap fix...A Grill Block

I am in texas so I left the three middle slots open. If you are in a very cold climate, you could most likely close all or leave one open. You will still get plenty of air from underneath the bumper. I have an air scoop on the passenger side with an air catch. I used some material I found and zip tied it on... cheap.

http://i205.photobucket.com/albums/bb97 ... P_0209.jpg

You can drag your cursor across the grill to see the placement

sleeve84028 · **Posted:** Tue Jan 22, 2008 9:45 am

Wouldn't driving slower be the real key to getting improved mileage from your vehicle? And I don't mean on the highway specifically either. I'm talking about around town. No super fast take off's at lights and start coasting around a lot more.

Jeepjeepster · **Posted:** Tue Jan 22, 2008 11:30 am

Thats the best thing you can do sleeve. It seems like everyone feels the need to FLOOR it and get to that next redlight so they can STOP again. People actually get annoyed if you dont FLOOR it and try to pass me, only to STOP right beside of me again. Doesnt make a bit of sense. :roll:

The HW dept around here also felt the need to raise the speed limit on most of the roads from 65mph to 70mph. I like going fast so I set cruise at 80mph which kills the mpg. If I slow down to 70mph it will go from 15-16(alot of hills) to 18-19. They should of taken a basic Physics class before they raised the speed limit, this would of saved alot of money, pollution, and gas.. Im dont really care though as Im not a tree hugger.

How will putting that in the grill help mpg darby?

jeepkj02 · **Posted:** Tue Jan 22, 2008 11:38 am

Jeepjeepster wrote:

Thats the best thing you can do sleeve. It seems like everyone feels the need to FLOOR it and get to that next redlight so they can STOP again. People actually get annoyed if you dont FLOOR it and try to pass me, only to STOP right beside of me again. Doesnt make a bit of sense. :roll:

That's so true! You hear everyone complaining that gas prices are too high, and then you see them driving 85 on the hwy! What's that about!

Albert · **Posted:** Tue Jan 22, 2008 12:14 pm

8 degrees last nite - 19 right now at 11:00am. It's not going to be above freezing for the next couple of days - per the weatherman.

My gas mileage has really gone down. I even ran a bottle of techron through it. 14-16 around town but a lot of ideling as it's too cold to shut it down. It's funny, i stopped at the 7-11 and every car there was running with no one inside them. Everybody inside left their vehicle outside running. I could have traded the KJ for anything................I can't believe more vehicles arn't stolen.

scoobysnax · **Posted:** Thu Jan 24, 2008 12:13 am

Why does mpg go down that much in cold weather? I know they use a cheaper grade of gas in the winter time but are you saying that it's worse when it's 5 degrees out compared to 30 degrees?

And then the next question is blocking out the grill will save mpg? so if i didn't care about looks and just put some cardboard in there that would help? If so why doesn't everyone do this?

Jeepjeepster · **Posted:** Thu Jan 24, 2008 12:52 am

More air gets put into the engine so more gas must be put in..

Cold air is more dense.

SoDakJeep · **Posted:** Thu Jan 24, 2008 2:57 am

yea its like -16 then add the wind -32 and i get crappy mileage i suppose leting the car kinda warm up for a little bit before i leave isnt helping much ither. i was not this bad during the warm summer months......o well....its a jeep not a honda

Albert · **Posted:** Thu Jan 24, 2008 9:56 am

Don't forget it's partly the winter blend gas to blame. At least around here anyway, 10% ethanol is added during the winter. It says so right on the pumps.

Sport · **Posted:** Thu Jan 24, 2008 10:14 am

ok so the colder air doesn't help with gas mileage but it does help with performance. That is why they make cold air intakes and alot of test tracks are in places that have cold climates.

I understand that you need an even air fuel ratio so increasing air flow will also increase fuel usage.

So would an intake acutally make things worse? I know I gained 1 MPG with my intake. The lowest I got was 14 now the lowest I get is 15.

indianrefining · **Posted:** Thu Jan 24, 2008 1:06 pm

scoobysnax wrote:

Why does mpg go down that much in cold weather? I know they use a cheaper grade of gas in the winter time but are you saying that it's worse when it's 5 degrees out compared to 30 degrees?

And then the next question is blocking out the grill will save mpg? so if i didn't care about looks and just put some cardboard in there that would help? If so why doesn't everyone do this?

Where did you get that information?

scoobysnax · **Posted:** Thu Jan 24, 2008 1:17 pm

Sorry, indianrefining, I guess I should clarify myself about "using a cheaper grade of gas." The “grade” of gas is still 87, but, from what I understand, it’s now a “winter blend” in the summer months it’s a “summer blend.” The winter blend is generally cheaper and the summer is more expense (wont’ that be fun to pay for once they switch back over again.) I don't know if this is done in all states or just the northern states (I'm in NYC.)

From what I understand the summer blend is used b/c it’s cleaner (in terms of it’s emissions) and b/c there are more cars on the road in the summer time than the winter. The winter blend is not as clean and uses more additives to maintain the same “grade” like 87 or 89 and so on. The extra additives in the winter blend from what I understand actually give you worse gas mileage.

At the end of the day it doesn’t make any sense to me b/c if we have clean fuel we should use it all the time and not just in the summer but that’s the Government for you.

So am I totally off base with my statement above? It's only based on garage talk and reading other posts on this site. And should this post be in the mileage section?

indianrefining · **Posted:** Thu Jan 24, 2008 3:50 pm

scoobysnax wrote:

Sorry, indianrefining, I guess I should clarify myself about "using a cheaper grade of gas." The “grade” of gas is still 87, but, from what I understand, it’s now a “winter blend” in the summer months it’s a “summer blend.” The winter blend is generally cheaper and the summer is more expense (wont’ that be fun to pay for once they switch back over again.) I don't know if this is done in all states or just the northern states (I'm in NYC.)

From what I understand the summer blend is used b/c it’s cleaner (in terms of it’s emissions) and b/c there are more cars on the road in the summer time than the winter. The winter blend is not as clean and uses more additives to maintain the same “grade” like 87 or 89 and so on. The extra additives in the winter blend from what I understand actually give you worse gas mileage.

At the end of the day it doesn’t make any sense to me b/c if we have clean fuel we should use it all the time and not just in the summer but that’s the Government for you.

So am I totally off base with my statement above? It's only based on garage talk and reading other posts on this site. And should this post be in the mileage section?

The feedstocks and the catalytic cracking process remain largely the same. 87, 89, and 93 octane fungible gasolines are the same octane and "cleanliness" regardless of time of year. You'd be correct in saying that the additive packages are varied, somewhat, depending on the time of year, the altitude, etc., but I wasn't aware that there was any significant difference in the cost of one package versus another.

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