need help diagnosing immediate 2mpg drop in fuel mileage after routine maintenance.
11-28-2008, 12:40 PM
#42
tom, have you tried PA90 in your rear diff? the stuff is like butter in my S13 kaaz 2way...just got it rolling today. the MT90 seems to be great in an S13 trans, but in my G35 it's not all that great on the first shift when cold. my remedy for now is to roll in 1st gear for a few seconds before shifting. after that it drives normally. the S13 is so loud i might not be able to hear every whine the transmission makes.
so how do i find out if i have a stuck caliper? i was able to install all brakepads with no problem. i noticed one rear pad had a little bit more rust residue than the otherside but the seal was intact and it pressed in and bled without a hitch. i guess i'll have to raise the vehicle up yet again. and recheck. yay for me.
i'm giving 50/50 to the fuel treatment and a stuck caliper
so how do i find out if i have a stuck caliper? i was able to install all brakepads with no problem. i noticed one rear pad had a little bit more rust residue than the otherside but the seal was intact and it pressed in and bled without a hitch. i guess i'll have to raise the vehicle up yet again. and recheck. yay for me.
i'm giving 50/50 to the fuel treatment and a stuck caliper
Some points to consider:
1) Idling your engine = Zero MPG Plain and simple. Ask anyone who knows - you can drive your car away after about 30 secs. Google it. Unless maybe you live in -40C/-40F then maybe you should plug your car in with a block heater and you still wont have to idle for more than 30 secs. Idling to heat up the car so you can have it defrosted and not **** freezing cold is hard on MPG and the environment but its up to you. Everyone has a different outlook on that issue.
2) Your MPG will be worse in the colder temps, prob about the 10% that you're seeing. Its a list of factors such as enriched fuel starts, longer high idle, colder oils and fluids to circulate, etc etc. I've never heard of someone getting better MPG in the winter.
3) it could be a possibility that you now have a fouled or leaky injector but I seriously doubt it. You could try pulling the plugs to see if there is one that is off color but if youre not experiencing a miss during idle or under load then youre prob fine. You would prob be getting a Check ENG light if you were getting that much unburned fuel in the exhaust??? Not sure?
4) Winter gas as stated above.
5) Car OFF, Park Brake OFF, Neutral. can the car be rocked back and forth on a level surface easily? It should be able to with a light push. If not you could have an issue with your new brake pads. Maybe they are binding and not retracting like they should...I had that on an 84 ZX and wore out one side at the rear in about 5000 miles. Had no idea at all that the pad was dragging...untill i started to hear metal grinding!!!!
I personally would not be too concerned with 2 MPG diff from summer to winter. I've been seeing that for years. However I live in Canada and its pretty cold up here. My Z however is in the garage hibernating till April LOL
1) Idling your engine = Zero MPG Plain and simple. Ask anyone who knows - you can drive your car away after about 30 secs. Google it. Unless maybe you live in -40C/-40F then maybe you should plug your car in with a block heater and you still wont have to idle for more than 30 secs. Idling to heat up the car so you can have it defrosted and not **** freezing cold is hard on MPG and the environment but its up to you. Everyone has a different outlook on that issue.
2) Your MPG will be worse in the colder temps, prob about the 10% that you're seeing. Its a list of factors such as enriched fuel starts, longer high idle, colder oils and fluids to circulate, etc etc. I've never heard of someone getting better MPG in the winter.
3) it could be a possibility that you now have a fouled or leaky injector but I seriously doubt it. You could try pulling the plugs to see if there is one that is off color but if youre not experiencing a miss during idle or under load then youre prob fine. You would prob be getting a Check ENG light if you were getting that much unburned fuel in the exhaust??? Not sure?
4) Winter gas as stated above.
5) Car OFF, Park Brake OFF, Neutral. can the car be rocked back and forth on a level surface easily? It should be able to with a light push. If not you could have an issue with your new brake pads. Maybe they are binding and not retracting like they should...I had that on an 84 ZX and wore out one side at the rear in about 5000 miles. Had no idea at all that the pad was dragging...untill i started to hear metal grinding!!!!
I personally would not be too concerned with 2 MPG diff from summer to winter. I've been seeing that for years. However I live in Canada and its pretty cold up here. My Z however is in the garage hibernating till April LOL
11-28-2008, 12:50 PM
#43
i'm from new jersey. i wonder if this year's winter fuel is different than the past years. my car has never seen lower than 19mpg since owning it brand new. now it's reading 17s sometimes high 16s. however, before maintenance it was the normal 19mpg. i filled up with a brand new tank, put it on jackstands, did the work and it immediately started getting 16-17mpg since rolling off the jackstands. hmmm...brakes? they rotated in my hands perfectly though..i'll keep checking and rechecking
11-28-2008, 01:34 PM
#44
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i'm from new jersey. i wonder if this year's winter fuel is different than the past years. my car has never seen lower than 19mpg since owning it brand new. now it's reading 17s sometimes high 16s. however, before maintenance it was the normal 19mpg. i filled up with a brand new tank, put it on jackstands, did the work and it immediately started getting 16-17mpg since rolling off the jackstands. hmmm...brakes? they rotated in my hands perfectly though..i'll keep checking and rechecking
11-29-2008, 10:28 AM
#47
# 1 don't use 2 bottles of injection cleaner. Thats a lil to much and can end up ruining seals. Plus only use it maybe once least every 3 months or every oil change, and on a full tank at that. To me 0w-30 is to thin of an oil for a 5w designed engine. Plus living in freezing NJ 0's not so good. (only my opinion)
How do you regularly drive? stop and go situations? What kind of gas are you using remember in NJ gas switches to oxygenated hindering mileage as well. Possible you've built up carbon and need to beat up the car a little on the highway, and check the plugs a minor tune up depending on how youd rive can cure most of those mileage issues as well.
How do you regularly drive? stop and go situations? What kind of gas are you using remember in NJ gas switches to oxygenated hindering mileage as well. Possible you've built up carbon and need to beat up the car a little on the highway, and check the plugs a minor tune up depending on how youd rive can cure most of those mileage issues as well.
11-29-2008, 12:24 PM
#48
# 1 don't use 2 bottles of injection cleaner. Thats a lil to much and can end up ruining seals. Plus only use it maybe once least every 3 months or every oil change, and on a full tank at that. To me 0w-30 is to thin of an oil for a 5w designed engine. Plus living in freezing NJ 0's not so good. (only my opinion)
How do you regularly drive? stop and go situations? What kind of gas are you using remember in NJ gas switches to oxygenated hindering mileage as well. Possible you've built up carbon and need to beat up the car a little on the highway, and check the plugs a minor tune up depending on how youd rive can cure most of those mileage issues as well.
How do you regularly drive? stop and go situations? What kind of gas are you using remember in NJ gas switches to oxygenated hindering mileage as well. Possible you've built up carbon and need to beat up the car a little on the highway, and check the plugs a minor tune up depending on how youd rive can cure most of those mileage issues as well.
12-03-2008, 05:10 AM
#52
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O2 would be a good place to start. I would be tempted to take it to a local tuner, and have it thrown on a wide band. Have the A/F ratio checked out...
12-03-2008, 06:23 AM
#54
true, i realize that fram filters might be crap. i've seen the many threads on it, but parts have to be made to a certain standard, plus certain guys here actually do run fram and have highly built motors and all my domestic friends swear by it lol. i figure i could run it for the winter. i only bought it because GC was on sale at autozone. my next change is already sitting on the shelf: GC/k&n oil filter.
as far as the drop in filter is concerned, i forgot to mention i've had a K&N drop in filter for about a year now. no problems with that. the rest of the car is stock.
oh yes, i also tried unplugging the battery a few days after the maintenance to see if that would help. i'm not sure it did anything...so here i am. thanks
as far as the drop in filter is concerned, i forgot to mention i've had a K&N drop in filter for about a year now. no problems with that. the rest of the car is stock.
oh yes, i also tried unplugging the battery a few days after the maintenance to see if that would help. i'm not sure it did anything...so here i am. thanks
www.bobistheoilguy.com is a great site to see info on this.
12-03-2008, 12:06 PM
#55
Is it possible you overfilled the engine oil? Overfilling the oil can make the crank drag through the oil (at least in a lot of cars, not sure on the 350 to be honest) and cause a decrease in mileage due to the increased effort needed to spin a crank through more oil than it was designed for.
12-03-2008, 12:10 PM
#56
Fram filters are not recommended by many including people who have tested them. They have a cardbord interior, and can fall apart. Research is a wonderful thing.
www.bobistheoilguy.com is a great site to see info on this.
www.bobistheoilguy.com is a great site to see info on this.
next change = k&n.
12-03-2008, 12:17 PM
#58
Is it possible you overfilled the engine oil? Overfilling the oil can make the crank drag through the oil (at least in a lot of cars, not sure on the 350 to be honest) and cause a decrease in mileage due to the increased effort needed to spin a crank through more oil than it was designed for.
12-16-2008, 07:01 AM
#59
quick update: so yesterday i did a fluid swap on my coupe. i replaced the MT90 in the trans with oem nissan manual transmission fluid, changed the royal purple in the diff with conventional castrol 80w-90 hypoy C, changed the engine oil back to my usual pennzoil platinum 5W-30 with fram EG filter. nav immediately showed around 19mpg (from low 17s). weird, mileage improved almost instantly, but this is only the first day of driving. i'll have to drive it more to see if it really helps. with the car on jackstands i installed my winter tire setup. perhaps those oils are better under racing conditions, but not for daily driving. clearly in my case, "if it ain't broke don't fix it."
Last edited by VQdriver; 12-16-2008 at 01:47 PM.
