Date:         Wed, 8 Mar 2000 19:53:01 -0600
Reply-To:     Joel Walker <jwalker@URONRAMP.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Joel Walker <jwalker@URONRAMP.NET>
Subject:      Re: gas consumption and guiness in the oil
Content-Type: text/plain; charset="Windows-1252"

> rebuild of about 40k on her. also to note, the oxs light does not come on
in
> the test mode or at all. i figured maybe a wiring glitch.  is it possible
> that the o2 sensor is bad and that is to blame for the poor mileage as
well

nah. the oxs light is nothing but a reminder. it's driven by a little box
down on the speedometer cable. some dealer likely applied the "fix" to it
years ago ... they cut the wires. this keeps the light from coming back on
every 60,000 miles (to remind you to take the bus to the dealer so he can
"check" the oxygen sensor).

> enough that i should just replace it?  what else could be to blame for the
> poor mileage?  she seems to run great.

ok, is this around-town mpg? highway-only mpg? both? my 87 camper, which
weighs in at about 4000 lbs, gets 14 mpg when i drive mostly in town on a
tank. this is because of the warmup period (the mixture is set very rich, by
the computer) and a lot of stop-and-go traffic on the way to work.
stop-and-go is the worse thing you can do for mpg. :( sitting at a
redlight/stopsign gets you ZERO mpg ... and that lowers the average (over a
tank) quite a bit.

it also takes quite a bit of power to get 4000 lbs rolling from a dead
start. once you're up to 60mph on the highway, it takes only about 15 hp to
keep you moving ... and you can get 18-20 mpg. more if the highway is pretty
level or you go a bit slower. :) i try to cruise at about 63-65 to keep the
mpg up. but even a short time driving in town drags that mpg back down. :(

also, you have to be careful about filling up ... if you do NOT fill the
tank up to the same spot/level each time, you really don't know what the mpg
is. example: let's say you filled it all the way up. slap-dab full. now you
go 250 miles. then fill up again. but this time, you're 1/2 gallon shy of
the same level/spot when you fill up. you get an false elevated mpg number.
say you used 10.0 gallons. that's 25 mpg you'd calculate. but if you had
filled it up to exactly the same spot, you really only got 23.8 mpg. not
much difference, but it shows that if you ain't accurate (in filling up),
the numbers are kinda meaningless (except as a "trend"). it works the other
way, too: let's say you filled up and were short of the mark. then you drove
250 miles and filled up again. this time, you went OVER the other
level/mark. this time you're a whole gallon more (last time: 10 gallons.
this time: 11 gallons). you'd get only  22.7 mpg. much lower than the 25 you
should get.

anyway, my point is that the mpg for any one tank is not really very
accurate and doesn't mean a whole lot. it's the trend of those numbers over
the months and years that matters. and you have to be careful about WHEN you
look at the numbers: winter mpg numbers are almost always a good bit lower
than summer mpg numbers, simply because of the warmup times. on my 87
camper, it varies as much as 4 mpg from december-january to june-july.

> secondly, yesterday i went to top off the oil b/c after about 2000 miles
she
> burns close to a quart.  when i took off the filler cap it was gooed up
and
> down with what appeared to be the foam of the great guiness.  it was thick
> and viscous and smelled like a weird oil.  after suddenly getting real
> thirsty and scratching my head i wiped it off the inside of the cap and
took
> out the fill tube and cleaned it up. what is it?  burned oil? but why
would
> it collect at the top of the fill tube? from engine pressure? i have never
> seen anything like it. is this common with the aircools?

it's normal. that stuff should look like brown mayonaise-froth. it's water
in your oil. it comes from condensation ... as the engine cools down at
night, the moisture condenses inside the tailpipe, muffler, and engine. the
moisture inside the engine runs down and gets into the oil. the water in the
exhaust system comes out as white steam in the morning when you go to work.
ever notice those other cars with steam coming out of their tailpipes? that
means they live close to where you saw them, and haven't warmed up enough to
evaporate last night's moisture out of the tailpipes. don't see much steam
at lunchtime, do you? :)

ok, the brown stuff is normal. what causes it is that you ain't driving the
bus long enough for the engine to get hot enough to boil off that water and
pass it out the crankcase vents. no big deal ... either change the oil more
often or drive it for 20 miles on the weekends. that's what i do: just take
it out on the highway and get up to 65mph and drive to the next exit (10
miles away), turn around and come back. if you prefer to change the oil, the
best rule of thumb is:

in Winter: change oil every TWO months or 2,000 miles, whichever comes
first.
in Summer: change oil every THREE months or 3,000 miles, whichever comes
first.

hope it helps. good luck!
joel