WTH is going on with my mileage??? - UPDATED with more stumpage!!!

[njmodi]

Originally posted by: Skoorb
I bet it's not alignment....

I second that.

More ideas (some are "out there"):

1. Could a slipping clutch cause something like this - i.e. higher RPMs in general because of a slipping clutch.

2. I just checked to see if there was a significant weight difference between the two tires, and the new tires are 2lbs heaver (each) than the ones you replaced. Not likely that would cause the drastic drop-off you are seeing.

3. Check to make sure none of the brakes are dragging - front and rear. You might have a stuck caliper or the parking brake (if you use it) cable might be kinked etc.

 

[OutHouse]

put the old tires back on (if you have them) and see if your milage imporoves. If it does then thats your problem. if not then you will know to put your attention to something other than the tires to find the problem.

 

[Don Vito Corleone]

Originally posted by: njmodi

Originally posted by: Skoorb
I bet it's not alignment....

I second that.

More ideas (some are "out there"):

1. Could a slipping clutch cause something like this - i.e. higher RPMs in general because of a slipping clutch.

2. I just checked to see if there was a significant weight difference between the two tires, and the new tires are 2lbs heaver (each) than the ones you replaced. Not likely that would cause the drastic drop-off you are seeing.

3. Check to make sure none of the brakes are dragging - front and rear. You might have a stuck caliper or the parking brake (if you use it) cable might be kinked etc.

The clutch is not slipping.

I'm surprised there's that much difference in the tires' weight, but it does seem unlikely to make that much difference.

I don't believe any brakes are dragging. I've had them checked recently and still had 80% of the pad material, even though the car has almost 48K miles. Also, I would think a dragging brake would cause brake fade due to boiling brake fluid, and haven't experience that at all.

 

[Don Vito Corleone]

Originally posted by: Citrix
put the old tires back on (if you have them) and see if your milage imporoves. If it does then thats your problem. if not then you will know to put your attention to something other than the tires to find the problem.

They were recycled months ago.

 

[OutHouse]

Originally posted by: DonVito

Originally posted by: Citrix
put the old tires back on (if you have them) and see if your milage imporoves. If it does then thats your problem. if not then you will know to put your attention to something other than the tires to find the problem.

They were recycled months ago.

go get another set of the same tires then

 

[chowmein]

check PSI of tires. that is where the problem lies.

 

[jagec]

Originally posted by: njmodi

Originally posted by: Kalvin00

Originally posted by: Maximus Power
A good can of octane boost to clean it out

Wasted money my amigo..

Unless you're referring to fuel injector cleaner...

Chevron Techron is what I would recommend for a good fuel system cleaner.

Seafoam for an everything-else cleaner.

As for the OP: No one seems to have asked, but are you sure these tires have the same diameter as the previous ones? Because if they are bigger, you'll notice what seems to be a fuel mileage drop, but really it indicates an inaccurate speedo.

 

[njmodi]

Originally posted by: jagec

Seafoam for an everything-else cleaner.

As for the OP: No one seems to have asked, but are you sure these tires have the same diameter as the previous ones? Because if they are bigger, you'll notice what seems to be a fuel mileage drop, but really it indicates an inaccurate speedo.

He replaced the tires with the same size. At least thats what the first post suggests. But an acute observation nonetheless. :thumbsup:

 

[Vic]

Originally posted by: sao123
Washington -> Minnesota = More hilly terrain?

HAHAHA!!

Washington is hilly and mountainous. Minnesota is flat. Elevation change between the 2 areas is minimal. The Puget Sound area of Washington ranges between sea level and 600 feet inside the major cities, while Minneapolis is at 800 feet. No big deal there.

My guess is that it's just winter gas and cold weather, although this is a considerable drop in mileage.

Question: are the new tires the proper size?

I noticed no change in mileage when I switched, on my WRX, from the amazingly craptastic RE92's at 205/55/16 to Toyo Proxes4 225/45/17 (with 17" wheels, I highly recommend these tires for ultra performance all-seasons btw). But my gas mileage does always go down 2-3 mpg in winter due to the formulated gas.

 

[Eli]

If you're trying to extend the life of your engine, use the stock paper filters, do not use AMSOil, K&N or similar filters.

They flow more air, they do not filter as well. Period.

 

[Don Vito Corleone]

Originally posted by: chowmein
check PSI of tires. that is where the problem lies.

No offense, but read the original post. I have always maintained factory-recommended pressure, and also experimented with overinflating the tires. Neither helped with the mileage. I use a high-quality brass tire pressure gauge, and measure pressure with cold tires.

 

[iamwiz82]

Are you running the defroster a lot? Defroster = AC.

 

[Don Vito Corleone]

Oh, and I bought the same size tires, 225/50-17s. Both tires have a V speed rating and are made by Bridgestone, so I'd assume they're identical, or at least very, very close in overall circumference.

 

[iamwiz82]

How windy is Minnesota? Lots of driving into the wind could hurt your mileage significantly. I see a 10MPG difference between driving with or against a 30mph wind.

 

[Vic]

Originally posted by: Eli
If you're trying to extend the life of your engine, use the stock paper filters, do not use AMSOil, K&N or similar filters.

They flow more air, they do not filter as well. Period.

I don't agree with this statement, Eli. The benefit of the oiled renewable filters is that they last MUCH longer (actually making them a good investment in the long run), and that they flow more air even when dirty.
Everyone knows that mechanics (and particularly quick oil change shops, whose employees are not mechanics) try to fool customers into believing that a dirty paper air filter can damage an engine by allowing dirt through, but this is completely untrue. What actually happens with a paper air filter when it gets dirty is that it clogs, reducing airflow and worsening power and gas mileage.
The renewable filters, like K&N's, do not clog anywhere as bad, and actually increase effectiveness over time (to an extent).
Also, paper filters can only filter at only layer. K&N style filters can filter over multiple layers. This means that they can flow better and still filter effectively.
Text

 

[njmodi]

Originally posted by: iamwiz82
Are you running the defroster a lot? Defroster = AC.

Another good point. To the OP, if you have the electronic climate control, and you always run it in "AUTO" mode, your A/C is always running.... this of course assumes you've changed the way you use your car AC/heating... but its just another thought. If you don't already do so, try running the heat in ECON mode (unless you need to defrost, etc.), and see if that makes a difference.

 

[iamwiz82]

Originally posted by: Vic

Originally posted by: Eli
If you're trying to extend the life of your engine, use the stock paper filters, do not use AMSOil, K&N or similar filters.

They flow more air, they do not filter as well. Period.

I don't agree with this statement, Eli. The benefit of the oiled renewable filters is that they last MUCH longer (actually making them a good investment in the long run), and that they flow more air even when dirty.
Everyone knows that mechanics (and particularly quick oil change shops, whose employees are not mechanics) try to fool customers into believing that a dirty paper air filter can damage an engine by allowing dirt through, but this is completely untrue. What actually happens with a paper air filter when it gets dirty is that it clogs, reducing airflow and worsening power and gas mileage.
The renewable filters, like K&N's, do not clog anywhere as bad, and actually increase effectiveness over time (to an extent).
Also, paper filters can only filter at only layer. K&N style filters can filter over multiple layers. This means that they can flow better and still filter effectively.
Text

The oilable filters allow bigger particles to pass through. There have been tests down and they allow a much "bigger" (still measured in microns) things in.

 

[Vic]

I've driven cars well over 100k miles with oilable filters and have NEVER had any type of engine damage or failure.

 

[jagec]

Originally posted by: iamwiz82
Are you running the defroster a lot? Defroster = AC.

I hate how auto manufacturers do that. I actually rewired my VW so I have an AC SWITCH, and I can choose whether I want my AC on or off.

 

[Vic]

Originally posted by: jagec

Originally posted by: iamwiz82
Are you running the defroster a lot? Defroster = AC.

I hate how auto manufacturers do that. I actually rewired my VW so I have an AC SWITCH, and I can choose whether I want my AC on or off.

Yeah, I really hate that as well.

 

[Scarpozzi]

I think it needs more cowbell.

 

[Don Vito Corleone]

Originally posted by: iamwiz82
Are you running the defroster a lot? Defroster = AC.

Not particularly. Just as in Washington, I only run the defroster until the windshield is clear, then switch to panel/floor vents. The car has automatic climate control, and obviously, being in MN, I have used the heat pretty much constantly for the last few months.

 

[psteng19]

Originally posted by: DonVito
Just to reiterate, because I keep seeing some things that are covered in my initial post:

- plugs are fine
- winter gas is not the primary explanation (the mileage dropoff happened in temperate weather in Washington)
- I have replaced the air filter, but I had been using a new Amsoil filter (similar to a K&N, but arguably better)
- tire pressure is fine
- the tires I replaced were also all-season, although they were "Sport" tires
-Minnesota is FLAT, much more so than Washington, and has no altitude of any significance

Is it possible my alignment is off, even if the car tracks straight and true? It has no tendency to pull to either side. That is the only suggestion that seems like a potential explanation to me, so far.

Thanks again for all the suggestions!

You never mentioned replacing fuel filter.

Also 2 lbs difference of unsprung weight at 4 corners could add up, esp. in lots of city stop and go driving.

 

[Vic]

Originally posted by: DonVito
- winter gas is not the primary explanation (the mileage dropoff happened in temperate weather in Washington)

The Puget Sound area switches to winter formulated gas on November 1st, regardless of the actual weather.

 

[Don Vito Corleone]

Originally posted by: Vic

Originally posted by: DonVito
- winter gas is not the primary explanation (the mileage dropoff happened in temperate weather in Washington)

The Puget Sound area switches to winter formulated gas on November 1st, regardless of the actual weather.

Interesting. Still, I have never noticed any meaningful mileage dropoff in the winter there, much less 6-7 MPG.