LS4 Performance - only getting 11mpg now that i installed my k&n intake?

I recently installed the k&n intake for the 5.3l imp ss and my dash is reading that I'm only getting anywhere between 10.9 and 11mpg? yes I get on it every once in a while but I'm generally not that hard on it.... Prior to the intake install my dash was reading 16mpg and this was with a little bit of me getting on it....Is my dash reading wrong because of the k&n intake now or is this a problem elsewhere? Any info would be appreciated. I also put 87 in my tank and yes I've experimented with higher octanes and no help....

Ignore the dash reading, as it can be inaccurate for a bunch of reasons. What's it getting when you do the calculation at each fillup?

It is possible to have issues after installing an oil-bathed filter like a K&N, as you can get excess oil in the MAF, which can affect mileage.

Then check the obvious...Is the vacuum line connected to the intake from front valve cover? If it's connected, check for leaks. Also, make sure the intake is on snug.

If that stuff checks out, I'd take the MAF off, get some MAF cleaner, and spray the inside down really well to clean out any oil and gunk that may be building up.

Lastly, don't EVER, EVER run 87 octane through these cars. You're losing double-digit HP by cheaping out on this, and it could be hurting your fuel economy due to retarded timing. Also, the near-constant knock your engine is most likely seeing will mean that carbon is building up inside the cylinders, making it even more susceptible to knock, even if you can't hear it.

^ I agree... sounds spot on since those intakes are oil based. A dirty MAF can cause bad mileage, the comupter could be sending too much/too little fuel if that's the case. Another thing that LS1 Racing said... don't run 87 under any circumstance.

Thanks for the info. I'll try everything you mentioned and I'll discontinue using the 87. What octane do you run in your ss?

Run 91/93 whatever the highest octane you can get at the pump

Run 91/93 whatever the highest octane you can get at the pump

What he said!!!

We can only get 91 in Socal, but I'm tuned for it.

91 in my 98 Z/28... I have yet to see 93 at the pumps in california? Not sure if they even have 93 at any station, I'm probably wrong but all the major cities I've been to don't have it. Run 93 if you can.

is there a noticeable difference with 91 and 93 both gas and performance wise? all we have here is 93 ( louisiana) but when i went to missouri for a week i was forced to use 91

is there a noticeable difference with 91 and 93 both gas and performance wise? all we have here is 93 ( louisiana) but when i went to missouri for a week i was forced to use 91

I ***believe 93 will burn slower/more efficiently. You should be lucky that you Have to use 93 hah. It's non-existant here in California.

What about 89? Any problems there? I've never really been able to get a good answer to that question.

There are a few towns that I have to go with my '08 SS that only have 89 as the top grade fuel. I normally use 91, but I have to run 89 at least once a month.

The car requires 91 your losing about 25+ hp using 87 as well as ireperable damage to your motor. Start there, a knocking motor is less efficient and therefore will waste gas Then try going back to stock intake. If that doesnt help its probably dirty or bad maf. Three easy steps one at a time for a week at a time. Disregard the dic. Let us know how it goes.

If you installed the kit to the instruction, I think you disconnect the negative of the battery. Give the car time to log more mileage data. I had the same problem when i put my K&N Kit on my impy.

I run 91 in mine. Ive tried 94 octane at Shell and don't seen enough difference for the price

If its not tuned for 94 u will see no difference as with 93. But if you were tuned for 94 you could get more timing out of the motor. Thus making more power. If I could get 94 I would.

Actually, these cars run a lot of timing from the factory, so I'm willing to bet that 94 will run just fine.

Running 89 in a pinch is fine, but the car will still see a ton of KR. You just don't want to expose your motor to it every day.

I didn't say 94 won't run I'm saying it won't make additional gains over 91 octane the car won't compensate for better fuel only KR for worse fuel.

Remember these car knocked bad with 91 oct and the factory tune guys. I run 94 all day everyday (5.00$ a gallon here)

OP: Def check out whats going on post installation. Maf , PCV , everyones told you. Other things to look at might be the 02 sensor , whats your milage?

Sadden is correct...On a stock tune, 91 knocks badly in these cars. I would venture to say that even 92 and 93 will show some measure of knock unless it's been tuned, meaning the more octane you can get, the better.

I have seen knock with 94 oct. Very little , but just goes to show....

My mileage is 88k. I'm gonna try to clean the maf this weekend. I will also try again with the higher octane.. I'll let.you guys know what happens. thanks again for your feedback

is there a noticeable difference with 91 and 93 both gas and performance wise? all we have here is 93 ( louisiana) but when i went to missouri for a week i was forced to use 91
i'm in missouri and we have a good mix of 91 and 93.... i've ran both depending on where i fill up and i dont see a difference... never dyno or anything but sotp feels the same, and i dont really see any differences in mileage. still i try and stick to 93 since it cost the same as 91.

My gxp was seeing rediculous amounts of KR on 93 with the stock tune, so honestly I would say any octane on the stock tune isnt doing you a favor. . .

Did you take out the honeycombing in the MAF? My buddy did that in his Aura XR after installing an aftermarket intake system and that killed his economy along with making his engine seem to struggle under load and it would idle pretty rough. He put it back in, reset his battery, and it smoothed everything out.

Just for reference all gases are not created equal, different gas stations will use difference refinement grades of gasoline. You need to find out if your gas station of choice uses a top tier gasoline, then you know that when you hit the "92" button you are actually getting 92 octane gas.

I had some fuels tested awhile back when a buddy of mine has his snowmobile melt down after getting premium gas at a local gas station, we were astonished by the fact that some of the premium fuels rated quite a bit lower than what they indicated at the pump. One said "93" octane, but came in at 88 octane when tested. In the end we determined that the fuel was the cause of the pre-detonation which in turn blew his sled up. Turns out that most gas stations have a clause that says they do not guarantee gas quality. Ha ha.

So anyway make sure you are getting gas at a big chain of stations, not your mom and pops place on the corner that is 4 cents a gallon cheaper. Up here we have Kwik Trip, BP Amoco, and Holiday that are pretty good, but Super America and some of the others are crappy.

I would put my scanner on my car after getting gas as various locations and would be amazed at how much knock I would get. I would run that tank almost dry and then put in good Kwik Trip gas and the knock would magically go away, both gases were 92 octane?

Did you take out the honeycombing in the MAF? My buddy did that in his Aura XR after installing an aftermarket intake system and that killed his economy along with making his engine seem to struggle under load and it would idle pretty rough. He put it back in, reset his battery, and it smoothed everything out.

Yeah, this is one of the worst so-called "mods" you can do on a MAF-equipped car. That screen straightens the air out going over the wire, and the sensor is calibrated with that mind. Removing it completely throws off the PCM and jacks up your feeling.

Back in the early LS1 days, circa 2001, I did removed the MAF screen on my 2000 Z28. Car had a ton of KR after that and lost some power. I wound up buying a replacement to set things right.

What about 89? Any problems there? I've never really been able to get a good answer to that question.

There are a few towns that I have to go with my '08 SS that only have 89 as the top grade fuel. I normally use 91, but I have to run 89 at least once a month.

i had to have my fuel trims re tuned when i put on my fender well intake, it would kick the mil light on per a daily basis saying bank one was too lean. even with running 91 (never ran lower but im sure it would make it worse)