[V8] Causes of Bad MPG?

[quattro + 5 or 8 = fun]

oh, one more idea.  i had a similar problem on a 20V.  drove me nuts.  when
through EVERYTHING.  turned out to be a muffler with a broken support inside
that blocked the exit.  also, i noticed several posted comments about oil.
that can make a big difference.  I have notice and increase and decrease of
mileage using the same viscosity but different brands of oil.  I used to run
syntec.  it went up when i switched to mobil 1 original formula.  then went
down when the switched to the newer formula.  i switched over to redline and
not only did my mileage go up by almost two mpg on the highway, but but my
consumption went down by half.  used to be about a quart every 1000 miles or
so.  now is down to 1.5-2 quarters every 4000 miles ( i change every 4000,
figure the redline will hold up and i no longer live in dusty rural WA
state, now in CA).  it has been a year since last drove my v8 due to the
fact that i am out of the country, but i believe the oil i use is a 20w50.
and, i do use it year round.  the Bay Area really never gets cold enough to
worry about putting a thiner oil in.  In WA however, it would be 100 in the
summer and -9 in the winter.  so i ran 10W30 in the winter.  also, what
about a plugged airfilter?  did u check that? and are u SURE your 02 sensors
are working?  i have have installed new ones a couple of times that were
bad.  if you used generics, did you crimp, solder, heat shrink and wrap the
connections?  if not, water on the crimps could be increasing resistance and
sending bad info to the ECU.  also, is the car running hot enough?  what
about doing a sea-foam treatment and running a couple of cans of techron
through the system.  if it has been sitting for that long, the gas is
certainly bad.  use it up, refill with premium and techron the drive the
piss out of it.  italian tune ups are not only fun, they work great to boot!




Shayne


PARTING:  1972 Mercedes Benz 280 SE 4.5
PARTING:  1986 Audi 4000 CS quattro


> From: Jason Wilkerson <wilke_jb at yahoo.com>
> Date: Tue, 9 Jan 2007 13:50:32 -0800 (PST)
> To: V8 list <v8 at audifans.com>
> Subject: Re: [V8] Causes of Bad MPG?
> 
> Ok, Wow - thanks for all the fast replies.  Lets see if I can address them
> all.
> 
>    Few notes:
>      - #2 seems to run the same as #1 - great.
>      - gutted cats - same as #1
>      - different wheels and tires on #2 but same OD as #1
>      - Plugs seem new, slightly brown and dizzys are clean - no misses
>      - Put FPR from #1's engine on #2 because I had it when I parted the
> car - was only about 10k old.
>      - No fuel smell
>      - Calculated actual milage on #2 at about 14MPG (showing 15.5 on
> readout - normal for a v8q)  If I remeber correctly #2 had about 18.5MPG
> calculated under the same driving conditions.
>      - I don't have a check engine light on (I don't have one but I have
> an LED attached at the floor - can't get the check engine light to work
> even with installing it in the dash - but that I think is un-related -
> even tried a new ECU), but I did check the codes when I first bought the
> car and returned nothing - the MPG has not changed since I bought the car
> - about 750 miles ago.
>      - The car did sit for about a year before I bought it - any Ideas
> what could happen over time to cause this.
>      - Oil and Coolant seem to be at a normal level - the Coolant seems to
> run a little hotter than on #1 and #2 has a new radiator and pump? it runs
> around 80c and #1 ran at 50c if I remember.
> 
>                 Thanks,
>                       Jason
> 
> 
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