Typically I get 400-450 miles per tank and just recently I'm only getting 300 miles per tank. No CEL codes and I'm gonna start looking into it today but I was wondering if anyone had some suggestions on where to start looking? I drive for a living so losing 100 miles per tank puts a pinch on my wallet, any help is greatly appreciated.

 

"30 miles per tank"???

Was this just a one time thing or consistent loss of gas mileage for the past few weeks? If it was a one time thing then don't worry about it, if not then: http://forums.maxima.org/showpost.ph...6&postcount=38

 

he probably meant 300...if its 100 miles off from 400-450

 

u probably driving faster....

 

Knock sensor would do it if you noticed a decrease in power along with the gas mileage. No CEL but you'd get a ghost ecu code. Also check your tire pressure, even a few PSI low can make a big difference (not 100 mile difference, but still).

 

pull codes even if you don't have a CEL, could/probably is a dead knock sensor. I watched my mileage slowly drop from 27 to 23, code came up, dropped in a new knock sensor, and some new o2 sensors (seperate code), now I'm back up to 27/28mpg

 

i am having this EXACT same problem....i was getting the same milage as you, 450-400 , and now im pulling barely 330....yesterday i checked the air in my tires and i was 15 below psi all around, so i filled them up, i checked the filter, its clean, i do have the EGR light going off in my car but i dont think that would do it....maybe my engine is throwing a really rich mixtrue for some reason. Im having a buddy help me out with it on wednesday so maybe all that will help....good luck and tell me if you find out anyhting that i havent thought of.

 

Are you saying you only had 15PSI or was it 15PSI below what you normally use? In either event its under 20lbs in all likelihood. You need to check your tire pressure more than once every 3 years. Try checking it monthly.

 

damn i only get that mileage if i drive like grandma (no WOT, no over 65, windows up, no launch, shift before 2500, etc)...i like spirited driving so i am usually on the low 20's ...21-23mpg.

edit: no codes of any type, normal PSI pressure, less than 2 months old both front 02 sensors (due to the old one's were stuck to stock y-pipe (yeah budget SS took over) ), chevron techron, mobil1 10w-30, just ran seafoam thru BB as a maintenance for carbon buildup, and clean TB.

need to do: IAVC valve clean and cone (PR CAI) wash and k&n cleaning kit application. <-- can this to be the reason of my mileage ? nah'

 

You should try running mobil 5W-30, not 10W30, particularly in the winter!

 

lol

murdoch i saw that coming....and i was 10-15 psi under what was needed..it just didnt look taht damn bad from the outside and i am lazy i guess. Your right i shold chceck it more than every couple decades so i will stay on top of that from now on....thanks for the support buddy...haha

 

well, no ghost codes, but I forgot to mention earlier that the car is idling about 1200-1300rpm which is way the hell to high. I know i can just unplug the TPS and manually adjust but I would like to find what is causing this high idle. There is no noticable power loss, so I'm thnking it's not a bad KS. I'm hoping the high idle and bad mileage are related, but I'm kinda lost on this one.

 

clean ur air filter

 

been there done that, brand new K&N

 

did u do the usual culprits? plugs, fuel filter, iacv, tire pressure, KS. the KS relieved me of 2mpg and the iacv strangely 1mpg. now i'm hitting 400 a tank through 70mph cruising, a couple WOT, and a/c. 50/50 city driving

 

plugs have about 5k on them, fuel filter is about 3 weeks old, iacv I'll look into, tire pressure was fine, even though my front drivers side looked low? ?_? I'm hoping it's not the KS I was quoted $115 for the damn thing today >_<

 

woot for another mpg thread