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chuckftboy · 11-06-2021, 06:49 PM

4 to 6 mpg is pertty typical for a large gasser. Often when we read about 8 and 9 mpg the owners ade driving smaller lighter coaches at 60 mph. I owned a 37 foot gasser with a 6 speed tranny and never seen over 6 mpg even on a good day, most ofter less. I useally drive at 70.

Fiesta48 · 11-06-2021, 09:06 PM

Fuel injection, overdrive transmissions, diesels and new emissions equipment will get 2-5 more mpg than old. Had an old 440 gas C class barely got 6 mpg. My '15 32k lbs DP pulling a car gets almost 9.

TheCatsRV · 11-06-2021, 09:13 PM

Will a (full) Banks system actually result in better fuel economy? I always thought it'd be a wash as you had more power and hence will use it. That said, I do have the full setup (fortunately didn't have to pay for it but had to get the headers regasketed with some bolt helicoil repairs) in my new-to-me Coachmen Mirada.

yeloduster · 11-07-2021, 06:34 AM

Quote:

Originally Posted by TheCatsRV

Will a (full) Banks system actually result in better fuel economy? I always thought it'd be a wash as you had more power and hence will use it. That said, I do have the full setup (fortunately didn't have to pay for it but had to get the headers regasketed with some bolt helicoil repairs) in my new-to-me Coachmen Mirada.

I had a 1988 P30 under a 32' Bounder. Stock it go ~5.5 MPG at 60 MPH. I added Doug Thorley Headers, Edlebrock Performer intake manifold and higher ratio rocker arms. I did all this in increments and measured the performance on a nearby hill. Each change added speed up the hill! My fuel economy didn't change.

I then added a Gear Vendors Under/Overdrive. When splitting gears the Gear Vendors had more impact on performance than all the other changes combined! With gear vendors overdrive engaged my fuel economy improved to ~7 MPG.

Soppy · 11-07-2021, 06:36 AM

The Banks System allows the engine to breathe freer and produce more Hp. Since the engine produces more hp at any given throttle opening . you will be be able to cruise with less throttle opening , burning less fuel. The extra power will help on grades as you may be able to remain in top gear without downshifting. How much of an increase will depend on how you drive , wind, load, and road conditions. Don't expect huge gains in fuel consumption.

Soppy · 11-07-2021, 06:38 AM

Quote:

Originally Posted by yeloduster

I had a 1988 P30 under a 32' Bounder. Stock it go ~5.5 MPG at 60 MPH. I added Doug Thorley Headers, Edlebrock Performer intake manifold and higher ratio rocker arms. I did all this in increments and measured the performance on a nearby hill. Each change added speed up the hill! My fuel economy didn't change.

I then added a Gear Vendors Under/Overdrive. When splitting gears the Gear Vendors had more impact on performance than all the other changes combined! With gear vendors overdrive engaged my fuel economy improved to ~7 MPG.

Did your 88 have a 3 or 4 speed tranny ?

yeloduster · 11-07-2021, 07:27 AM

Quote:

Originally Posted by Soppy

Did your 88 have a 3 or 4 speed tranny ?

Soppy, I forgot to mention that I also did a cold air intake taking air from directly behind to grill into the carb. I have not seen any hard data showing that the Banks system has any performance advantage over systems built with headers and mufflers from other manufacturers. Banks may be better quality and last longer or better warranty but not better performance.

HEADERS IS HEADERS!

My P30, like all carbureted P30s had a TH475 3 speed transmission.

Quote:

Originally Posted by TheCatsRV

Will a (full) Banks system actually result in better fuel economy? I always thought it'd be a wash as you had more power and hence will use it.

TheCatsRV question is a good one. My experience with multiple trucks is that if you add power to a truck under load you will tend to use the extra power and the MPG stays about the same. My fuel economy increase on the '88 P30 Chassis came when I added an overdrive that slowed engine RPM from ~3000 RPM @ 60 MPH to ~2600 RPM @ 60 MPH. I'm sure there are exceptions and some of you have experienced better fuel economy. It depends largely on where you live and how you drive.

CountryB · 11-07-2021, 07:49 AM

Quote:

Originally Posted by Flyer15015

it had a carby 454, and a 3 speed TX, and got 6-7 MPG at 60 MPH @ 3200 RPM. A year into it, and I changed the rear end third member at a shop in Denver. The next 5 years she got 9-10 MPG @ 60 MPH @ 2600 RPM.

Similarly, if you just go to taller tires (like from 29" OD to 31") if they fit, is like doing a gear ratio change. You get lower rpm at highways speeds and that can increase mpg at that speed, but the trade off is you have worse "take off" power (slower getting up to speed).

Dav L · 11-07-2021, 08:02 AM

Make sure the RV is in good maintained state and drive it.
Trying to get more MPG is a waste of $s unless you drive it a ton.
The mileage will be what it is.

If it's carbureted, I would consider an aftermarket EFI setup that will improve mileage, but also drivability and more importantly, reliability. Holley and others sell kits.

TheCatsRV · 11-07-2021, 09:57 AM

Quote:

Originally Posted by yeloduster

Soppy, I forgot to mention that I also did a cold air intake taking air from directly behind to grill into the carb. I have not seen any hard data showing that the Banks system has any performance advantage over systems built with headers and mufflers from other manufacturers. Banks may be better quality and last longer or better warranty but not better performance.

Not sure what the higher volume air intake really does as I don't think one drives a RV WOT like a muscle car (or at least I don't/don't plan to). What may help is a better intake manifold/plenum-runner but that's more costly to buy and install over a (cold) air filter runner. Cooler air would help, higher air density is effectively increasing engine displacement.

Quote:

HEADERS IS HEADERS!

Can be work maintaining them, keeping the bolts tight. Not that the V-10 Triton is that great stock with manifold warping issues.

Quote:

TheCatsRV question is a good one. My experience with multiple trucks is that if you add power to a truck under load you will tend to use the extra power and the MPG stays about the same.

Exactly. One may be able to realise better fuel economy by driving gently but the temptation is to use what you have (which may result in even poorer economy).

GLT3 · 11-07-2021, 04:44 PM

Thanks to everyone, and you have convinced me to continue looking for a diesel and what I would like to find is a small 30 ft to 32 ft with a 5.9 and 6 speed allison but those are few and far between, again thanks to everyone

TheCatsRV · 11-07-2021, 04:59 PM

Be aware of diesel maintenance (not forgetting acquisition) costs. The increased economy will pay only if you drive it enough.

Unplanned Tourist · 11-07-2021, 05:36 PM

Quote:

Originally Posted by GLT3

Thanks to everyone, and you have convinced me to continue looking for a diesel and what I would like to find is a small 30 ft to 32 ft with a 5.9 and 6 speed allison but those are few and far between, again thanks to everyone

Worrying about fuel costs is like worrying about not getting the last drop of coffee out of your cup in the morning.

Comparing the overall costs of any MH, gas or diesel is redundant IMHO.

Adding up all the costs of purchase, taxes, insurance, maintenance and repairs and the fuel prices will be just a drop in the bucket.

Getting what you can afford with a floorplan you like are the 2 biggest things to consider.

Crasher · 11-08-2021, 10:21 AM

Quote:

Originally Posted by GLT3

Thanks to everyone, and you have convinced me to continue looking for a diesel and what I would like to find is a small 30 ft to 32 ft with a 5.9 and 6 speed allison but those are few and far between, again thanks to everyone

There are certain advantages to owning a DP, however, lower overall cost of ownership is not one of them. You will get better fuel economy, but your purchase cost and maintenance will be higher than a gasser would be. Just be sure to set aside a larger "What If" fund.