[T3] great weekend drive

[Bryon Garvin]

Well, I went from feeling happy about 34 mpg, to worried that something's
wrong :(

I'll check the spark plugs.  Would low fuel pressure cause it to run lean?
 I'm trying to think of what else to check?  I had 29-30 psi 2 years ago
when I checked it.  I'll put the gauge on again.

I have a small tear in the large intake bellows at the rear of the engine.
 I need to replace that....but the reason I ask is because if it's running
hotter than it should due to something like that, does that in-turn cause
the engine to run lean?  In other words, does a hot engine consequently run
lean?  I think I understand that a lean-running engine will likely run
hot....I'm just wondering about the other way around.  All cooling tins,
spark plug seals, etc are in place.

The only other thing I have changed is that I just went to straight 30w oil
with ZDDP.  This is the first tank I've gas I've used up while running that
oil as well.  I'm thinking that probably has nothing to do with good
mileage.  Previously I used 10w40 or 10w30 depending on the season.

Tires were 20/30 (front/rear)

 - Bryon, '71 Fastback


On Tue, Sep 6, 2011 at 7:30 AM, Jim Adney <jadney at vwtype3.org> wrote:

> On 5 Sep 2011 at 23:12, Bryon Garvin wrote:
>
> > I did have the 12 point star driver and a torque wrench and did them to
> 25
> > ft-lbs.  I think I read that right in the Bentley.  If did that wrong,
> > please tell me.
>
> I just checked, too, and that's exactly right.  ;-)
>
> > I felt that it was tremendous mileage and much better than I expected.
>  But
> > I guess if it matters, remember that it was ethanol-free, 92, and I was
> > driving no more than 60 mph because of the roads that I take to get there
> > and probably 1/3 of it was around 50 mph.  There was a somewhat of a
> > tail-wind on the way, but really, I was fighting some buffeting from the
> > side most of the way there.  I'd basically say "no" to having a tailwind.
>
> Your 34 mi/gal still seems high. I did tests a few years ago driving
> at 65 and 60 and got about 28 and about 29 respectively (with gasohol
> in an AT '73) but I was driving the same cars in the 70s when almost
> all gas was ethanol free and never got close to 30 unless I had a
> tailwind. Ethanol has about 10% less energy content and there's maybe
> 10% ethanol in your gas, so the overall difference in energy content
> is 10% of 10%, which is only 1%, or less than we can usually measure.
>
> The change in energy content only becomes noticable with high
> concentrations of ethanol, like E85, which you shouldn't be using.
>
> If your odometer was slipping, that would reduce your mileage, not
> increase it. Filling the gas tank to the same level, before and
> after, is critical to this measurement.
>
> > I'm interested to hear your response Jim because currently, this would be
> > the best mileage I get out of any of my cars on the highway and that
> > includes my 96 Jetta.
>
> I'm surprised, but pleased, that your Jetta doesn't do better. Which
> engine does it have? If it usually goes on trips where you can travel
> at 70 mi/hr +, then that makes a significant difference.
>
> > I'm going to keep driving to this station and running 92 ethanol-free
> just
> > to see what the around-the-town mileage is.  I don't mind paying that
> money
> > at this point if I'm getting that kind of return on the investment.
>
> The 21 mi/gal you get around town is exactly what I get around town,
> so that seems to indicate that there's nothing really wrong with your
> car. If your car is an MT, then that would give you a couple mi/gal
> edge, especially on the road.
>
> I hope you'll do more trips and get us more data. I'll be pleasantly
> surprised if the 34 mi/gal number holds up as a long term average.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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