Exceptional Mileage

[whc03grady]

We took two trips in Ludwig this Summer, ca. 2400 and 600 miles long.
The odometer stopped working somewhere in Eastern Nebraska, but we kept track of the 'where' and 'how much' of fill ups so I could Google Map it later. I came up with an average of 17.65 mpg for the 2400 mile trip. That's pretty freaking good.

Then I did the 600 mile trip and came up with 19.823 mpg. Is that even possible? It did include 200 miles of US 12 in Idaho, which as anyone who's driven it can tell you, is gonna severely limit your top speed (it's extremely winding).

The bus was heavily loaded in both cases.

[sped372]

How fast were you going? That seems to be the biggest factor with these things... I average 23mpg cruising at 57 all day long.

[whc03grady]

There was plenty of 70-75 mph driving on the long trip, and a lot of 45-50 mph on the shorter one.

[Jivermo]

I got about 21 MPG on my trip this summer, on interstates, going about 62-65 MPH. When I got into the mountains, back roads and town, it dropped down to just under 18 MPG. I was very pleased with the gas mileage and performance. I love the fuel injection system of my '78 bay, especially now that I have an understanding of how it works. Neat Stuff!

[whc03grady]

For whatever reason I assumed 16 mpg was going good guns. Ludwig's exceptional mileage was perhaps not so exceptional after all.

[Westy78]

I got about 21 MPG on my trip this summer, on interstates, going about 62-65 MPH. When I got into the mountains, back roads and town, it dropped down to just under 18 MPG. I was very pleased with the gas mileage and performance. I love the fuel injection system of my '78 bay, especially now that I have an understanding of how it works. Neat Stuff!

I would hazard a guess that if you're getting 21mpg at 65mph that you're running on the lean side. Depending on driving conditions of course. If you had tail winds the majority of the time maybe you're mixture is all good but I'd rather see around 18-19mpg average to feel safe about not cooking my heads.

[Jivermo]

Adjusted the AFM and valves when Colin was here, and have a Dakota Gauge on #3. Plugs look good. I'll keep paying attention. The mileage goodness dropped rapidly over 65 and with headwind and hills.

[Westy78]

Adjusted the AFM and valves when Colin was here, and have a Dakota Gauge on #3. Plugs look good. I'll keep paying attention. The mileage goodness dropped rapidly over 65 and with headwind and hills.

Well if you have the DD gauge and all looks good with the head temps I'd say motor on and enjoy that killer MPG. For a Bus that is. =D>

[Amskeptic]

Adjusted the AFM and valves when Colin was here, and have a Dakota Gauge on #3. Plugs look good. I'll keep paying attention. The mileage goodness dropped rapidly over 65 and with headwind and hills.

Well if you have the DD gauge and all looks good with the head temps I'd say motor on and enjoy that killer MPG. For a Bus that is. =D>

Chloe has given me very good gas mileage for 60 mph with a singleport, 21-22 mpg.
BobD I just could not keep it under 65-70, for 16-18 mpg.
The Road Warrior (whc03grady's set-up) usually was cooking at 70 and gave me 17-19 most of the time.

My Type 4 buses punished me with lousy fuel mileage at high elevations, 13-15 mpg. Chloe seems not to care.
Colin

[drober23]

I've been getting 17 -18 mpg lately, which is a bit better than I normally get. I hooked up the air-fuel ratio sensor today and noticed I was running 13.8 - 14.2 at highway speeds! This may explain my somewhat elevated CHTs along with the somewhat better than average mileage.

I normally got around 16.

[Amskeptic]

I've been getting 17 -18 mpg lately, which is a bit better than I normally get. I hooked up the air-fuel ratio sensor today and noticed I was running 13.8 - 14.2 at highway speeds! This may explain my somewhat elevated CHTs along with the somewhat better than average mileage.

I normally got around 16.

If you are willing:

Rotate mixture screw in AFM in half-turn increments towards rich, no more than one adjustment per day, and let us know what happens to your CHTs/fuel ratio readings.

Remember that highway speed a/f ratios are incredibly sensitive to invisible effects of subtle gradients and wind resistance.
If you can insert one 50-60 mph full throttle acceleration per above adjustment schedule, you no longer have variables of wind or gradient, and we all get a snapshot of your torque peak a/f ratio. If you time the full-throttle acceleration at each mixture screw position at the same level stretch of road, we may be able to glean which full-throttle ratio provides best power. My butt says 11.9-12.3 gives best power on the BobD, but I suspect something isn't true.
Colin

[tristessa]

The most recent long-ish trip I've done was Portland->Maupin via The Dalles, where I averaged 20.5 MPG for the entire trip. I ran mostly 70-75MPH and a few stretches of 80MPH on I-84 to & from The Dalles, which is mostly-flat three lane freeway, and 60-65MPH with a couple of 50-55MPH third-gear grades and a short stretch of 75MPH on Hwy 197 from The Dalles to/from Maupin, which is up-and-down curvy-at-times two-lane highway.

.. but I've got such a mutant beast that these numbers are probably irrelevant to anyone else. =D Still, I've gotten 22-23MPG on flat interstate when I remember to keep my foot out of it and cruise 55-60MPH .. but where's the fun in that? It's flat boring interstate designed to get you from Point A to Point B as "efficiently" as possible, and I don't like getting passed by Winnebagos...

[Amskeptic]

The most recent long-ish trip I've done was Portland->Maupin via The Dalles, where I averaged 20.5 MPG for the entire trip. I ran mostly 70-75MPH and a few stretches of 80MPH on I-84 to & from The Dalles, which is mostly-flat three lane freeway, and 60-65MPH with a couple of 50-55MPH third-gear grades and a short stretch of 75MPH on Hwy 197 from The Dalles to/from Maupin, which is up-and-down curvy-at-times two-lane highway.

.. but I've got such a mutant beast that these numbers are probably irrelevant to anyone else. =D Still, I've gotten 22-23MPG on flat interstate when I remember to keep my foot out of it and cruise 55-60MPH .. but where's the fun in that? It's flat boring interstate designed to get you from Point A to Point B as "efficiently" as possible, and I don't like getting passed by Winnebagos...

What your numbers tell us is that a VW bus takes the same gasoline calories to move no matter the engine.
Colin

[tristessa]

What your numbers tell us is that a VW bus takes the same gasoline calories to move no matter the engine.
Colin

True enough, though I never got mileage quite this "good" with the aircooled 2.0L that was in it before, and not at the "high" speeds I find myself driving at with the "extra" power -- it cruises comfortably at 75-80, where before 70 was about it and 75 felt like I was really pushing it. But OTOH, I've done a lot of other work between then and now in the front suspension & steering, rear suspension, better tires...