Gas Milage Goes from Suck to Blow

[ojmagg]

I used to get about 14 mpg. The last few tanks I've gotten about 11. I know that the winter gas blend could affect the milage, but this just starting happening...I think they change the blends around Nov where I live. My tires are up around 35 psi. I've 65,000 miles and have never changed my plugs...the engine runs silky smooth...Could it be the intake gasket...

Any other thoughts on likely sources would be much appreciated.

[Amnesia]

Here is your $0.99 diagnostic. (And welcome to my world.)

Get a can of carb. cleaner and while the engine is running, spray it along the intake manifold mating surface. If the engine speed changes then you've found a leak.

One other thing to check that I've had a problem with on mine, are dragging brakes. Go for a normal drive for 10-20 min. Then get out and feel the heat coming off of each rotor through the wheel spokes. If you had a brake caliper that isn't releasing properly, there'll be noticably more heat coming off of that rotor. (For more precision, use a digital, non-contact, infared thermometer.)

Good luck!

[VehiX]

Could just be that you're warming the VX up in the morning and letting it run when it's cold. So even though your not driving it and tracking milage, your still burning gas.

I've noticed bad gas milage since my VX starting throwing codes for the EGR!

Also check the air in your tires at least once a month during the cold season.

[CrazyCzech]

I think I get 16-17 city and about 20 highway in my VX. Thought it was bad, but reasonable for about 245HP I'm supposed to have with the intake/exhaust upgrade (compared to a BMW 525i with 220HP, getting 18/24).
I hope I do not see a decline like you are describing, I'd expect 11mpg on a V8. I noticed decline driving on a highway in the Power Mode.

[xdfarrx]

Your VX has 245 hp huh? Please digress how...

[Y33TREKker]

It depends on your priorities. Better mileage would be nice, but I've always preferred to think first of the smileage I get from my VX.

[blacksambo]

Try some Lucas gas treatment to clean your injector nozzles. It always works when our mileage declines.

[CrazyCzech]

Well, I guess I'd have to put it on dyno to convince myself and others, if I cared.
Specs say that stock VX is about 210hp, my exhaust/intake is supposed to be giving me extra 35hp. So there you go.
Either way, my worst mileage yet was 16 city which was the whole point of my post.

[Y33TREKker]

Either way, my worst mileage yet was 16 city which was the whole point of my post.

Given the weight of the VX, that actually sounds about normal, especially for city driving. Maybe it's just time for a tune-up, like air filter and new plugs (as you say they've never been changed).

[JHarris1385]

The 100K iriduim plugs should be good.

I would
1. Clean the egr
2. Drain some gas from your tank to make there is not any water in it.
3. Air filter
4. Just other basic stuff.

Or better yet get a scangauge from TONE like I did to know your true MPG. Im hoping your math was right on those figures.

[MZ-N10]

i get about 16 now, was getting close to 18 when i used it daily. do wat ^^he said, and u might also want to change tranny fluid, diff fluids and blinker fluids

[VehiX]

Well, I guess I'd have to put it on dyno to convince myself and others, if I cared.
Specs say that stock VX is about 210hp, my exhaust/intake is supposed to be giving me extra 35hp. So there you go.
Either way, my worst mileage yet was 16 city which was the whole point of my post.

I know you don't really care and sorry to get off topic, but that's at the crank not at the wheels.

Cyrk and johnnyappollo dynoed there's previously.

Quote from that thread:

"johnnyapollo has a 01 Proton with:
- Powervault generation 1 catback exhaust
- HotShots Air Intake
- Trans Interceptor Shift Kit
Not sure if they plays at all into it, He is running stock 18x7in rims w/ 255/55/18 Scorpions
His best of 3 runs was: 153.04 Max Total Power & 174.13 Max Total Torque"

Link to thread with dyno chart and pics:

http://www.vehicross.info/forums/sho...highlight=Dyno

[CrazyCzech]

Big difference, I guess I need to start saving for the supercharger.

[JAFO]

2. Drain some gas from your tank to make there is not any water in it.

Not to go off on a tangent, but what would water do to fuel economy?

I am fimilar with pouring water down the intake to steam clean the engine to remove carbon buildup. I have heard that some run water injection.