Drop in MPG's

[crager34]

For years I have been getting, rather consistently, 15 - 18 & sometimes 19 MPG's for my city and highway driving. Most recent maintenance items include a new radiator, fuel filter, regular oil changes.....

I had one CV boot tear and so I went ahead and replaced (myself) all 4 boots. Everything has been fine visually (no grease leaks or oozing), but since then..... I now get 12 - 13 MPG. Seriously, the next tank full of gas after the CV boot change is when it happened. I don't feel any drag when coasting in neutral, no motor noise changes, but it does seem like I hear a bit more "road" noise from the front.

Now I am still unemployed and money is tight, so I just can't take it to a mechanic and say fix it. I am hoping for some thoughts as to what this could be and what I should check out. Almost 170,000 miles on the VX and I am pretty solid with preventative measures, but this one has got me stumped.

Thanks for your input in advance.

[Cris]

Same thing happened to me. If you split the axle make sure that the axle seated together. You have to make sure that the little wire snap ring that holds the two halves together locks! if your using the same one its real hard to put back together. Look at them both should be centered same distance side to side.

[vt_maverick]

Can't you find a mechanic who would give you a free quote? There's another thread going right now where a guy has spent significant time and a growing amount of money trying to find a problem on his own and he's finally concluded he needs professional help. Sounds like you've got the mechanical abilities to maybe fix it yourself, so what does it hurt to ask for help in the diagnosis? Even if you had to pay $50 to get that diagnosis, you'd easily save that in unnecessary parts costs as you try to whittle your way down to the answer.

[Ldub]

I'd guess winter blend fuel is the culprit & the CV boot repair was just coincidental timing.

[Gussie2000]

I agree with larry.
Winter seems to decrease mileage on our VX. I also noticed an huge decrease on MPG since winter kicked in.
The higher density of the colder air is causing our VX to consume more fuel due to higher degree of oxigen so the ECU readings on the air/fuel mix in the combustion chamber is more intense

[Jolly Roger VX'er]

I get 60 miles "easily" on the first quarter tank during warm weather and it drops to about 45 miles during winter months. This equates to around 120 miles on the first half tank in warm weather and around 100 miles during winter.

But, I'm sure with 170k miles you've probably noticed the drop in mileage during the colder months.

Be sure that your caliper sliders are working freely. This one bit me in the behind years ago when my rear, inner brake pads were "dragging" due to the sliders not releasing entirely and thus I burned up my inner pads...ruined my original rotors...and was wondering why my mpg had dropped. I never noticed because it was both sides thus it didn't pull to either side while driving. Also it was the inner pads so the outer pads looked good as well as the outer rotor looked fine.

Also, you might benefit from a new fuel pressure regulator. My mileage shot up when I changed it.

Make sure your air filter isn't due for replacement. Mine is a K&N that can be cleaned and oiled and every time I do mine my mpg jumps to the good.

These VX's are very sensitive to tire pressure when it comes to mileage. If you run a lower pressure for a better ride your mpg will suffer.

Bear in mind all this stuff adds up. I spent an afternoon on my VX going through stuff that affects mpg and I gained like 2mpg when I was done.

Also...its possible since your engine now has 170k...it could be carboned up internally and could benefit from some sort of "de-carbon" maintenace such as "SeaFoam" treatment. My local garage offers a de-carbon service for like $65 where they inject something like SeaFoam into your engine while it runs and black carbon blows out your tailpipe. I've never got this done myself but have used SeaFoam as per the directions and seen some carbon blow out the exhaust. I've heard people claim that the professional service yields restored performance & mpg's.

[MSHardeman]

Did you have to remove the front rotors from the spindle to get the boots replaced? If so, did you set the pre-load correctly when you tightened the axle nuts down? Could be too tight causing drag.

[tom4bren]

Crager,

Didn't you move at about the same time as the boot replacement? I'm only asking because the fuel "winter mix" is state regulated, not Federal. You may be experiencing a worse mix than you've been used to in the past (more ethenol).

I'm assuming that you followed the boot install instructions posted here so you didn't pull the shafts out of the axle tubes. True?

What kind of boots did you install?

When I put on MechaTechs, it seemed to me that they only provided about half the amount of grease that you should be putting in (IMHO). The good news is that you don't need to tear it all the way down again if that's the problem. Just cut the large band off of each boot and pull it back to schlep some high quality synthetic grease in there & then replace the band. Careful cutting the band tho ... don't damage the boot.

[crager34]

Did you have to remove the front rotors from the spindle to get the boots replaced? If so, did you set the pre-load correctly when you tightened the axle nuts down? Could be too tight causing drag.

Did not remove the rotors.

Crager,

Didn't you move at about the same time as the boot replacement? I'm only asking because the fuel "winter mix" is state regulated, not Federal. You may be experiencing a worse mix than you've been used to in the past (more ethenol).

I more or less moved back from Aiken, SC to Cincinnati and worked the CV boots shortly after.

The gas makes the most sense to me, because I KNOW I did a good job on the CV boot change out. I did notice the lack of grease the new boots came with, so I bought some extra and really gooped it up before putitng it all together. Going to look at DIY Carbon/Fuel System cleaners then look at getting it professionally done and see if there is really a difference except for price.

I hate this, becasue it's got in my head that if the VX starts to go bad, then I need to look at another car and it probably won't be another VX. Those thoughts make me feel dirty.

[tom4bren]

I hate this, becasue it's got in my head that if the VX starts to go bad, then I need to look at another car and it probably won't be another VX. Those thoughts make me feel dirty.

They have meds now for lunitic thoughts such as those.

[nfpgasmask]

Did you have to remove the front rotors from the spindle to get the boots replaced? If so, did you set the pre-load correctly when you tightened the axle nuts down? Could be too tight causing drag.

That was my initial thought too, Mark. If you over tighten those hub nuts, you will be adding to the amount of force needed to turn things up front, thus, hurting MPG.

Bart

[crager34]

Well? A $10 can of Sea Foam with about 10 gallons of gas in the tank and I am back up to 150 miles at 1/2 tank. Meaning, when I put the Sea Foam in the tank I was just at 1/2 tank with 100 miles on the OD.



I hope that did the trick and thanks for the quick replies and helpful information.

[Mile High VX]

Well? A $10 can of Sea Foam with about 10 gallons of gas in the tank and I am back up to 150 miles at 1/2 tank. Meaning, when I put the Sea Foam in the tank I was just at 1/2 tank with 100 miles on the OD.



I hope that did the trick and thanks for the quick replies and helpful information.

You'll want to be changing that fuel filter soon if you ran Seafoam through the gas system...it can get clogged pretty quick. Might just buy one and keep for later, or in case you need it sooner...

[blacksambo]

Lucas gas treatment also boosts milage.

[Mile High VX]

Lucas gas treatment also boosts milage.

I use it with every fillup...