Author Topic: Gas Mileage: 350  (Read 19970 times)

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Offline temple_rat

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Gas Mileage: 350
« on: December 22, 2008, 10:19 AM »
Sent: 3/15/2005

We just completed our 700 mi. maiden voyage in our 82 minnie (carbureted 350 chevy w/HEI ign.). It was very comfortable to drive, has plenty of power and was elated when my girlfriend calculated our mpg at 11! But alas, she inadvertently added an extra 100 to the total miles. So my elation was dashed on the rocks when I realized our mpg was closer to 8.5 traveling 60-65 on the hwy. I'm looking for ways to improve the MPG and am wondering if its realistic to get over 10?

TomT.

Offline denisondc

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Re: Gas Mileage: 350
« Reply #1 on: December 22, 2008, 10:21 AM »
Sent: 3/15/2005

99% of the time there is plenty of air flow and turbulence below the carburetor to atomize the fuel mixture.
   Your fuel mileage of 8.5 sounds about normal for something as wide, high and non-aerodynamic as an RV.  Keeping the carb and plugs and wires in good shape, letting it lose speed on upslopes, and planning ahead to have your speed higher when reaching the beginning of a long upgrade, plus driving a little slower in the right lane and letting the other traffic go on their way, are about all you can do.
    It won't amount to much.    Our largest single expense on a long vacation is the gasoline cost.

Offline Froggy1936

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Re: Gas Mileage: 350
« Reply #2 on: December 22, 2008, 10:24 AM »
Hi,

After a 6000 mi trip in my class C 350 chev I averaged 8.92 MPG Avg speed 65 MPH.  The very best I got was 12.1 @ 55 MPH level road for a couple hundred miles w cruise control no A/C.  This is with the stock Quadrajet carbuerator and Turbo 400 3 speed transmission
Veh weighs 11220 GVW.  Frank.
"The Journey is the REWARD !"
Member of 15 years. We will always remember you, Frank.

Offline ClydesdaleKevin

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Re: Gas Mileage: 350
« Reply #3 on: December 22, 2008, 09:45 PM »
Yep...I've said a few times before, but our rigs were geared to get maximum fuel economy at the highway speed limit...which was 55mph when our rigs were made.

Drive 55...its will greatly increase your fuel economy, period!

Also, as Denison said, keep up with your tune-ups.  Plugs, wires, cap, rotor, points if you still have them...keep them in good working order and properly adjusted, and your economy will be maximized.

Another also:  Keep your air filter CLEAN!!!  It makes a big difference!

And finally, keep your oil changed frequently...I change mine every 3000 miles...and use the proper viscosity!  A lot of folks, us included before I knew better, think that using a heavier oil will slow down annoying oil leaks...and it does...but it also makes the engine work a LOT harder!  I'd rather put in an extra quart every 1000 miles using the SAE 30 that I use in Excalibur than lose up to 2 miles per gallon but save a half a quart of oil...lol!

For our driving and climate conditions, since we essentially "snow-bird" as fulltimers, the manufacturer's recommended SAE 30 is ideal.  Look at the chart for your engine, and then figure out the ambient temperature on average when you drive your rig the most...and use the lightest oil recommended for your engine.  A few quarts of oil are MUCH cheaper than MANY gallons of gas.  Just check your oil before every trip and every time you stop...which is what you should be doing with our old rigs anyway.

Kev
Kev and Patti, the furry kids, our 1981 Ford F-100 Custom tow vehicle, and our 1995 Itasca Suncruiser Diesel Pusher.

Offline TommyM

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Re: Gas Mileage: 350
« Reply #4 on: January 20, 2010, 05:53 PM »
I have a 1975 GMC G30 chassis under a 21' Midas Class C motorhome, with a 350 engine and a TH350 trans. I don't remember the weight, but it seems like it was in the 8000 lb range.  I can look it up if anybody wants to know.  I bought it in June, 2000.  It's taken its last trip, and I'll be pulling the engine out this weekend because I sold it (I'm parting out the rig).

In that time, it made probably 8 or 10 trips back and forth from the Dallas area to Colorado, and a gazillion local trips in the Durango area.  I've driven it 70 mph+ on the freeways, and foot-on-the-floor over Wolf Creek Pass and other steep climbs around here.  I kept it in good tune, and mostly kept up with oil changes. 

Over that time, I drove a total of 15,265 miles, and used 1,977.534 gallons of fuel, for an average of 7.72 mpg.

I hope someone finds this helpful, or at least moderately interesting.

Tommy
Durango, CO
'75 Midas Class C (parted out, scrapped)
'85 27' Chieftain (crashed!)
'86 33' Chieftain (sold)
'94 37.5' Elante 37RQ
Durango, Colorado

Offline Froggy1936

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Re: Gas Mileage: 350
« Reply #5 on: May 17, 2015, 07:43 PM »
On my recent trip to Trap Pond my 1977 Winnie got 9.5 MPG W the 4L80E W OD and convertor lock up and TBI FI from the 1995 transplant . Serpintine belt worked perfectlt with new bracket. Frank
"The Journey is the REWARD !"
Member of 15 years. We will always remember you, Frank.

Offline bluebird

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Re: Gas Mileage: 350
« Reply #6 on: April 29, 2016, 06:24 PM »
I'd say you were getting about all you're going to get with a carburated 350 in those years. As Kevin said they were designed when the 55 mph was enforce in the USA. Pickups didn't do a whole lot more than that back then. I'll bet that engine didn't make over 160 hp.

Offline Froggy1936

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Re: Gas Mileage: 350
« Reply #7 on: April 29, 2016, 07:52 PM »
Reread I have a 77 mini with a 95 5.7 TBI  injected W a 4L80E  trans W OD and lock up TQ . The old 350 W Quadrajet could get 12 MPG @55 MPH @100K mi  Frank
"The Journey is the REWARD !"
Member of 15 years. We will always remember you, Frank.

Online Oz

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Re: Gas Mileage: 350
« Reply #8 on: May 01, 2016, 01:47 PM »
This isn't the topic to troubleshoot problems.  It's about what gas mileage people are getting.