Author Topic: Gas Mileage: 454  (Read 108231 times)

Offline bluebird

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Re: Gas Mileage: 454
« Reply #125 on: April 03, 2017, 05:05 PM »
Actually my Challenger with the throttle body injection did better on fuel than the Daybreak with port injection. It also had more pep from a stop sign, not that I pushed them much. I would have thought just the opposite looking at the body shape. The Daybreak sat lower to the ground and had the slanted nose, so I thought that it would have cut the air better. The Challenger had 35,000 less miles on it too. 

Offline Winnebago Warrior 94

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  • Year: 1994
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  • Engine: 454
Re: Gas Mileage: 454
« Reply #126 on: April 04, 2017, 07:49 AM »
Thanks for yalls help ..I hope my winnebago  warrior  gets as good of  gas mileage   or or a little better being as mine is a 22ft ..my hubby didn't open the top on what he said looked like a carburetor . .he just noticed it when he was changing the air filter..I don't know alot of proper mechanical  terminology . .but I don't mind getting  my hands dirty and I like to know and find out info about things ..I did change out the wiper blades ..lol :)clap 

Offline Elandan2

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Re: Gas Mileage: 454
« Reply #127 on: April 05, 2017, 06:33 AM »
That's probably the most important. It doesn't matter how well it runs if you can't see where yer goin'   :)
Treatzall Waste tank sanitizer, lighting, and other RV related products!
Rick Ellerbeck, 1977 Elandan II

Offline Winnebago Warrior 94

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Re: Gas Mileage: 454
« Reply #128 on: April 05, 2017, 10:48 AM »
That's probably the most important. It doesn't matter how well it runs if you can't see where yer goin'   :)
good one  :D  and true story ...lol.I also called Chevrolet  and they said it is fuel injected I'm ready to check out the gas mileage . .I need to get insurance  and get it inspected   

Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #129 on: April 05, 2017, 11:43 AM »

A lot of lessons learned here, summed up nicely regarding mpg's:

https://rv-roadtrips.thefuntimesguide.com/rv-gas-mileage/

Offline goldfinger1958

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Re: Gas Mileage: 454
« Reply #130 on: January 01, 2018, 02:15 AM »
Im very new to the RV world ,except for my slide in camper,I just bought my 1988 Tiffin  Allegro ,its 27 Ft.The last owner had the bus about 20 years  he said if i was in the flats and no heavy foot i would see 14mpg some,but overall he said look for about 9.5mpg ,he documented about everything and that bus was his baby,but his health failed we got it pretty cheap at4 grand,we have the 454 like most do.It has 77k miles on it and is still carb for fuel.IT RUNS SO SMOOTH ,brings back the70s real qucik.Ill post my real numbers  once we get out on the first trip.
thanks for the great site.

Offline TerryH

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Re: Gas Mileage: 454
« Reply #131 on: January 01, 2018, 02:23 AM »
Wow!
14 MPG?
Even 9.5 ?
Please, please, share the secrets!

Offline Rickf1985

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Re: Gas Mileage: 454
« Reply #132 on: January 01, 2018, 09:59 AM »
A 27 footer I could see 9 max but 14?!!!! That was quite a sales pitch. Or on the flats with a STRONG day long tail wind. I have experienced that with tractor trailers, but you always have the days of opposite winds where you are driving all day INTO the strong wind so it offsets in the long run.

Offline 1990HR

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Re: Gas Mileage: 454
« Reply #133 on: January 02, 2018, 12:47 AM »
We went on a 1600 mile trip and averaged 7.23 MPG. I don't think that's too bad as there was 4 of us and we were loaded up pretty good.

Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #134 on: January 02, 2018, 09:14 AM »
That seems about right, but I don't put much faith in anyone's numbers unless I can see all the data.   Mine are here: http://www.fuelly.com/car/chevrolet/p30/1990/tmsnyder/454843


Set up an account and every time you fill up, send a text to fuelly with the odometer reading and the # gallons.  It's very easy, and free.   And then we can all see what fantastic mpg's everyone is getting LOL  Otherwise I'm a skeptic.  Mid 7's is realistic.  But double digits? Show me the data.


It's very common for someone to calculate their mileage based on one fill-up after driving only a few hundred miles, gently, downhill, with a tail wind and all the tires fully inflated.   Then claim that that's their mileage while they hammer down the road at 75mph, into a headwind, with tires they haven't checked in months still claiming  'Oh yeah, I get 13mpg!'










Offline RickNC

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Re: Gas Mileage: 454
« Reply #135 on: January 03, 2018, 12:08 PM »
We took our first long road trip just before Christmas in our 1995 warrior 23. 1367 miles RT.  Used 140 gallons of fuel which works out to about 9.7 MPG.  ~Flat roads and 90% interstate. Cruise set  mostly on 65mph. 15-20 gallons fresh water. Two people and a 20lb dog.  Prior to the trip all plugs/wires cap/rotor were replaced. TBI system cleaned and serviced. Tires ~77 psi.

Offline legomybago

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Re: Gas Mileage: 454
« Reply #136 on: January 03, 2018, 05:54 PM »
We took our first long road trip just before Christmas in our 1995 warrior 23. 1367 miles RT.  Used 140 gallons of fuel which works out to about 9.7 MPG.  ~Flat roads and 90% interstate. Cruise set  mostly on 65mph. 15-20 gallons fresh water. Two people and a 20lb dog.  Prior to the trip all plugs/wires cap/rotor were replaced. TBI system cleaned and serviced. Tires ~77 psi.
At 23' your weighing in around 10k?? I would say your at the "optimal" mpg for a P30 chassis rig, due in part to not weighing a lot and having TBI and you probably have overdrive?
But on 14,000lbs +/- a 1,000, a carburetor, and a TH400, your back to 5-6.5 mpg depending on how/where you drive and what you are towing. That's been my experience anyway, out in the wild west.
Never get crap happy with a slap happy pappy

Offline WrigleysBraveWin

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Re: Gas Mileage: 454
« Reply #137 on: January 10, 2018, 10:09 AM »
1994 23’ Brave with 454 Chevy and Banks Power Kit and going from Vegas to Chicago I was able to get 11.6 MPG and when I ran the foothills in Missouri I was at  10.2 MPG ..... For sure my best mileage came when I traveled about 55 MPH
Today is the youngest you'll ever be!

Offline legomybago

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Re: Gas Mileage: 454
« Reply #138 on: January 10, 2018, 12:10 PM »
At 23' your weighing in around 10k?? I would say your at the "optimal" mpg for a P30 chassis rig, due in part to not weighing a lot and having TBI and you probably have overdrive?
But on 14,000lbs +/- a 1,000, a carburetor, and a TH400, your back to 5-6.5 mpg depending on how/where you drive and what you are towing. That's been my experience anyway, out in the wild west.
I'm still curious what the gross weights are, and if these rigs have overdrive with fuel injection. At least overdrive?....
Never get crap happy with a slap happy pappy

Offline Rickf1985

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Re: Gas Mileage: 454
« Reply #139 on: January 10, 2018, 03:04 PM »
Overdrive can be a double edged sword. It can give better mileage on flat ground with no headwind but it is generally dropping the engine down pretty low in the power band so you will be lugging the engine on hills and into the wind and therefore using more gas there.

Offline Winnebago Warrior 94

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Re: Gas Mileage: 454
« Reply #140 on: February 09, 2018, 10:12 PM »
My 94 Winnebago warrior is fuel,injected and not sure about the overdrive ..not sure about the gas mileage but I will be finding out soon ..I got my belts changed today and I got my new awning installed and transmission fluid and filter changed ..I drove it. Around 65 miles and used less than a 1/4of a tank .. :) ..I do need to get me some new tires especially on the front ..mine are 2007 ..so time for new ..next will be,my paint job ..ylpee

Offline Rickf1985

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Re: Gas Mileage: 454
« Reply #141 on: February 10, 2018, 09:41 AM »
hat is only 260 miles per tank roughly according to the gauge so don't get your hopes up to high. That said you cannot base your mileage on the gauge, you have to go by fill ups and true mileage ideally from a GPS. And you have to do it over several fill ups. On a 94 you probably do have overdrive.

Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #142 on: February 12, 2018, 07:48 AM »
And you may have to correct for your odometer.   Easy to do, just note the odometer reading as you pass a mile marker.   Then after 100 miles or more, see how far off you are .  Then correct your odometer reading.   Especially if you changed tire sizes (diameter) it can be off.



Biggest factor though is you have to drive some significant miles, not just a couple hundred.


Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #143 on: April 07, 2018, 07:58 PM »
We just did a trip to Florida and back to Buffalo, over 2500 miles and got the following on all my fill-ups. 


6.76 mpg
7.32
7.79
7.73
7.76
7.43
7.80
7.38
7.53


This is a 454 chevy, edelbrock carb, recurved distributor, towing nothing, 40 gallons of water in the tank, and I drive between 60-65 mph.  All except the first one was highway, pretty hilly along some sections of the route. 


All the data are here: http://www.fuelly.com/car/chevrolet/p30/1990/tmsnyder/454843


Average over the 13,458 miles for which I've logged every drop of gas is 7.3 mpg.






Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #144 on: April 15, 2018, 01:14 PM »
Just as a sanity check to put my mpg numbers in perspective, I was wondering what is the Maximum possible mpg I could ever expect from my motorhome.  It's actually a fairly simple calculation.  I assumed:


Air at stp
No other hp losses, just air resistance.
8' wide by 9' tall front area
Flat road


Different shapes experience different resistance to air flow, and this is quantified as a drag coefficient.  I  considered worst case though best case.  Worst case = a brick shape, Cd=1, this is pretty much what I have.   Modern cars can get down to 0.3 or so, my RV is nowhere near that, it does have a little bit of a sloped nose.  Best case, I only took it down to 0.6.  I can't imagine an RV having a better Cd than 0.6.


For engine efficiency, there are published values for how many lb/hour of fuel are burned per hp made by the engine.  For gas, they vary from 0.45 to 0.50.  This would be for an engine that is in tune and well maintained.   If not, all bets are off obviously.


By my best SWAG (scientific wild a$$ guess), I'm thinking my Cd~0.8, and engine is about 0.47 lb/hr/hp, I could only ever see 8.5mpg at 60mph.  That's the max mpg I could ever get from the rv just considering air resistance, no other frictional losses.  I'm getting 7.5mpg now, so even if I spent a bunch of money on engine mods, I'd be running up against this hard limit to fuel economy.  I was thinking about installing a wideband oxygen meter to check on my carburetor tune, but now I'm reconsidering it.  $200 to try to eek out a few tenths of an mpg doesn't seem worth it.


It resulted in an interesting plot that came out of the analysis, I'll try to post it.   It verifies as mentioned many times in this thread that if I'm willing to drive slower, the mileage can increase. 


One way to change the Cd of the motorhome might be to change the shape of the air flow around the back end of the coach using airtabs.  They are about $200 for a set.  Without them, the whole back end of the coach is a large low pressure area, pulling back on the coach.  Airtabs are supposed to disrupt this and create a shape behind the coach similar to the trailing edge of an airfoil.   Kind of like the fold-out shapes on the back ends of tractor trailers that you find on the interstates these days.  Might be worth trying them out, there are some threads on this website that claim that they do actually work.







Offline Rickf1985

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Re: Gas Mileage: 454
« Reply #145 on: April 15, 2018, 06:29 PM »
They do work but make SURE you put them on in the right direction!! They do NOT go the way you would think they do.


And that drag coefficient is figured at sea level and 75 degrees and 45% relative humidity and no wind so transfer all of that to real world figures where you will very seldom, if ever, see those conditions your figures are probably pretty close to the mileage that you are getting right now. I am impressed with the consistency of your mileage, it is very close on every tank.
I have to start from scratch on my distributor and timing settings again this year. I also need to buy a new advance timing light. I like the quadrajet but I think I am going to go with a Performer manifold and carb, That carb is just so much more adjustable. And that way I also get rid of the EGR and all of the associated passages and crossover heat.

Offline tmsnyder

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  • Engine: 454
Re: Gas Mileage: 454
« Reply #146 on: April 23, 2018, 01:20 PM »
That sounds like a fun project! 


I want to play with my edelbrock too, with an O2 sensor to try to milk some more mpg's out but based on my fluids calculations there's not a lot to gain there just based purely on wind drag. 


Maybe a Duramax swap, or that 7.3L you have .... :)

Offline WrigleysBraveWin

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Re: Gas Mileage: 454
« Reply #147 on: May 18, 2018, 08:41 AM »
Fuel Injection... 94 Brave, 23’ ..... 464 with Banks Kit ..... Best mileage at 60mph 11.6 ..... Average in Mountains of Missouri 10.2
Today is the youngest you'll ever be!

Offline tmsnyder

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Re: Gas Mileage: 454
« Reply #148 on: May 29, 2018, 01:01 PM »
Kept it 60 mph or less and drove another 660 miles this weekend.  Usually I ran it at right around 58 mph.  From Buffalo to Syracuse (flat), down through the Pocono mountains with some pretty good hills, and back.


8.6 mpg
8.2 mpg  (some of this was running the generator about an hour)

Offline udidwht

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Re: Gas Mileage: 454
« Reply #149 on: August 09, 2018, 02:53 AM »
Fleetwood Southwind Storm 28ft 454 TBI w/4L80E trans


Renton Highlands, WA. to Blaine, WA. I netted 8.75 mpg with an average speed of 58mph. Overdrive in these rigs is a bit of an oxymoron. I usually just keep it in D due to the hills here. It does just fine MPG wise. No towing.


The best I netted was from Renton Highlands to Medford, Or. with a 10.04mpg. A lot of flats. Spped again at 58mph. No towing.
1994 Fleetwood Southwind Storm 28ft
P30 454 TBI w/4L80E
57,XXX miles and counting....

 

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