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Old 08-06-2016, 06:53 PM   #1
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Location: Wilmington, MA
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Mileage, with a twist?

I have seen a few threads talking about gas mileage.
I have a Fleetwood Southwind, 1988, that I got a couple years ago.

Unfortunately, I only get to use it a few times a year at this point. One typical use would be a weekend trip to nearby Maine. (about 150 mile round trip)

I have run it a bit here at the house, for tune up and other testing. I run the generator from time to time.

I still have yet to do a major tune up, and plan to do the typical plugs and distributor parts. I still need to replace the elements in the fuel filter and other maintenance items like this...

By the way, it is powered by a Chevy 454.

The Genny is a 6.5 Kw Onan that runs from the main fuel tank.


Here is the real reason for the thread. I have run about 187 miles since last fill up. I took it camping in Maine last month, and will again next weekend. So, I go to the gas station, and put in 52 plus gallons.

I do not have the exact numbers in front of me, but do recall that I figured the miles per gallon at about 3.4, perhaps 3.6 mpg. (I do not recall exactly)

To me, that is not too good.

Now, I will say it seems to run fairly well, but if I am very heavy on the accelerator, it does seem to chug a bit. If gentle on the accelerator, it runs smoother, and will maintain highway speeds with little problem. I know it is a big mh (35 feet) and the gas engine is working pretty hard.

This next trip, I am considering towing my Lincoln MKX. I suspect that will not improve the mileage at all!

So, I have not recorded the hours on the generator this tank, but would be surprised if there were any more than 5 hours this tank. Most likely less.

How do I know how much gas is consumed by the genny, and how much by the main engine?

It really does not matter that much. I own what I own, and will eventually tune it up as best I can, but I am resolved to the fact that what I own is not particularly efficient.

Also, that last trip to Maine was in heavy traffic for hours, leaving the Boston area last time. The trip home was more uneventful, but I recall very slow traffic on the way up last time.

Any advise or comments are welcome.

Karl I. Sagal KarlSagal@Gmail.com
Well done is better than well said. (Ben Franklin)
1988 Fleetwood Southwind, 34'
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Old 08-06-2016, 06:59 PM   #2
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I think too small a sample to provide fuel miles per gallon.

Someone will probably come along and provide a generator estimate. I think about quarter to half gallon per hour. Load depending of course.

Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
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Old 08-06-2016, 07:03 PM   #3
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It takes many, many miles to get an accurate figure. After 46,000 ours is 7.6 mpg, not including generator use. Our 1999 35' Santana w/460 got 5.0 to 6.5 over however many miles we drove it.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
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Old 08-06-2016, 07:15 PM   #4
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Gas in the tank , if over a month old will provide poor mileage , without stabilizer. Gen set consumption would be approx. a 1/2 gal per hour.

You would need , fresh fuel , after your tune up and a smooth; no stop and go or heavy foot; run to get a true MPG reading.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
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Old 08-06-2016, 09:19 PM   #5
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A year ago I put a fresh 460 V8 in my 33' Holiday Rambler. On the 875 mile drive from San Marcos TX to Sierra Vista AZ, doing between 70-75mph, I got about 6mpg. On my recent 390 mile drive to Capitan NM with cruise set at 65mph I got 7.6mpg. I don't use my 7KW Onan generator that much but according to research I did it consumes about 3/4 gallon per hour (which is one reason I don't use the gas hog much).

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