I've had it with this horrible Gas Mileage! Idea's?

[Numba1goalie]

Alright. So 13.6 MPG is just not cutting for me. I have tried a lot of different methods of curing this problem like SeaFoam, Acetone, cleaning my EGR Valve and throttle body.

So now I am here, asking for help. Any ideas how to cure this? If I can fix it though I am gonna have to sell this beauty.

Thanks guys!

[nocturnalVX]

No worries...
Sell the Heep & get a economy car to use as a daily driver. I ride motorcycles as much as possible, and (with that gas mileage @ 35 - 40 mpg) it evens out nicely.

[psychos2]

have you checked your intake gaskets ? shawn

[Amnesia]

I know what you mean about the mileage. Mine is like a spoiled little kid. It gets what it wants, when it wants.

When I first got my VX it had around 36K on it and I was pleased as it seemed that I always got at least 17-18mpg... really close to 19 oftentimes. Then it just got worse. It has just under 100K on it now and I've tried everything I can think of except the intake gasket. In the past 10K miles, I've gotten anywhere from 13mpg to a best of about 16.9. At its worst I was stone dry at 220 miles. At best, I've gone a little over 370 on a tank, without having to walk.

It's in the shop right now w/ TOD problems & it's getting the valve cover gaskets replaced (under warranty - warrantybynet.com... hopefully this solves my oil comsumption problem), so when I get it back I'm going to check for vacuum leaks around the intake. You might check your brake calipers. In the past 10K miles I've had to replace 3 out of 4 of my stock calipers, due to sticking. You could smell and feel the heat coming off the rotors after you drove only a few miles. I picked up one of those non-contact, point & shoot digital thermometers and found that the offending calipers had rotors on them that were in the 600'F - 800'F range... as opposed to one on a good side that was only around 94'F on the same trip.

Best of luck!
Shawn

[VehiGAZ]

Good suggestion on checking the brakes!! Basically, anything that's dragging unnecessarily or not properly lubed will reduce your mileage, too. I'd suggest you have them change all drivetrain fluids (transfer case, differential, etc) and repack the bearings while they're at it, too. Good luck!!

[thedutchguy]

HEAVY RIGHT FOOT ?

[blacksambo]

I don't know if you've changed your air filter to something more exotic than the OEM, But believe it not that seems to make a difference. We have two '99 VX's with similar miles (70K+). One has a K&N the other OEM. OEM gets better mileage but doesn't sound so throaty or have the quick throttle response. Somebody once said on this sight that performance=lower mileage. They were right. Get back to original specs and you can get 20 mpg. It works for us.

[Numba1goalie]

Well I have 66k on mine now.

at 50k i had all the fluid changed. at 62k I had the wheel bearings repacked (another try at getting better mileage).

I also have a K&N filter, but I don't have a heavy foot by any means, and 90% of my driving consists of to work and back which is strictly highway.

I will check into the intake gasket. I do know it looked like it had some black film around the gasket last time I was under the hood.

Also that is a good idea about the brakes, I know when i turn around corners I get alike a wearing sound coming from the front.

[Joe_Black]

Plop an Isuzu 3.0L turbo diesel in there in place of that gasser and you'll always be in the 20+ MPG club. Plus you can make your own fuel too if you want. You should be able to recoup the cost within 1 - 2 years of driving, even sooner if you sell your good gasser to someone else.

[Numba1goalie]

How nice, any real ideas how or why it's getting 13 MPG? Someone mentioned a while back that its because the 3.5L is a high horsepower high tourque engine but i dont buy that because look at the 350Z and Infiniti with the "ok" gas mileage their running.

[Joe_Black]

You unfortunately probably have an engine that's in the bottom economy percentage. As mentioned above there are a great number of things to check on to eliminate unnecessary mechanical and aerodynamic drag, but there's also the possibility your engine just isn't at the top of the curve. Consider it's the same engine mass-produced for a great variety of Isuzu and Isuzu-supplied applications. Not all of them that make it successfully through testing and quality control are going to continually operate at peak efficiency. Some are going to work fine, be reliable and last as long as the best, but consume more fuel. Maybe the intake runners are slightly out of spec, the fuel map in the ECU corrupt, too much resistance in the sensor harness... any number of things you'll never find out while it dollars you to death looking to save pennies in fuel.

Cynical view? More realistic, based on experience. Take ten of the exact same mass-produced vehicle with sequential serial numbers and you'll find inconsistent economy and performance data. That's the nature of mass-production. Our beloved VX's are hand-built limited editions, but our drivetrains aren't.

Do the simple, inexpensive things to see what helps then assess where you feel the problem truly rests if you don't see improvement. You may simply have a thirsty 6VE1.

One thing I'm not clear on, and I can't find the info in this thread, is has your VX always had poor economy or did it just start happening all of a sudden?

[marcosv6]

Are you running stock size tires?

[Ldub]

(snip) because look at the 350Z and Infiniti with the "ok" gas mileage their running.

That's attributable to less weight & wind resistance. The VX isn't very big, but she's a heavy little pig.

[psychos2]

It could also be the O2 sensors. If they are reading lean when it is ok they will add fuel. shawn

[Numba1goalie]

No im running stock size tires.

Thats a good diea witht he O2 Sensors. might be a little bit early, but it could be worth it, I will have to work on pricing.

All in all, I love this car as much as most of you here, that why I want to get the best of out her and be happy with the economy of it as well. I'm sure most of you understand.

On another note, I thought maybe the fact we have 4.33 gears it might be another case, but then i think about how im only going 70 and cruising at 2800 RPM's, that may not be the best excuse.

Another thing, the FX35 which may not be as heavy get from what I've heard 23-24 MPG highway. I would think with the amount of horsepower it has less the weight should equal out to vehicross standards? maybe so?

any more input helps, thanks again for your ideas!