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Old 09-19-2011, 11:31 PM   #41
Join Date: Jul 2009
Posts: 46
Year: 1987
Coachwork: International
Chassis: International
Engine: International 6.9L diesel
Rated Cap: 71
Re: Whose getting 10+ mpg and what engine is it?

Originally Posted by nearhomeless
Narrowing things down in my bus search. I know there is a best engine thread I started, and also a mileage thread but the mileage thread doesn't say what engine you had so..

I'm hearing people with Cummins 5.9 and Cummins 8.3 report 10mpg or above so far. Is there anyone getting lower mileage with those engines? Is anyone with other engines getting 10mpg or better? Please post, I want to see how common these observations are, and under what conditions. (speed, hills, loads) I kept telling myself "well I dont plan to drive it much at all" but if I plan to put 10,000 miles on it over the next few years, that alone would pay for a $2000-4000 difference in fuel or even a whole 'nother backup bus.

So this is JUST for people getting 10mpg reliably at highway speeds (55mph counts), what is your engine?
The Cummins 8.3 6CTA, ISC, ISL are large engines around 1900+/- pounds plus a transmission to handle that kind of horsepower is needed. THATS some serious weight.
Everything about a schoolbus is marginal except the brakes. Those things got great brakes! ! !
Unlike commercial freight, kiddies dont pay much when being hauled short distances twice a day.
So buses are made JUST beefy enough to get them there and back.

The weakest link are those terrible tiny Allinson 545 automatic transmissions used in buses and RV's and BREAD delivery trucks.

An allison MD 3060 is much better as it is a bit beefier and has a final drive ratio that gives Over Drive capacity and an extra few MPH on the highway. They are found used and rebuilt on Ebay fairly cheaply.

Then you have to have a driveline that will handle those extra ponies.

You're NOT gonna ever spin the wheels on a skoolie. If you try, you're looking to make a $1000.00 mistake or more....
You'll be lucky to get away with only a popped U-joint.

So IF you put the pedal down on an 8.3L Engine, somethings gotta give and it most likely will be the drive shaft or U-joint.

I saw the results of a friend's new employee, that was trusted to drive a large tandem flatbed, after he tried to spin the wheels with a large Caterpillar. The 6 inch diameter drive shaft looked like a pretzel or a piece of play dough a giant had played with.
That was an expensive weekend for Ernie, and Bozo the Clown was looking for a new job.

When the engineers put these things together, engine, CLUTCH, tranny, driveline and rear-end, its all got to be compatible,
horse power-wise. Some leeway is there but you have to play with it carefully..

If you do decide to put an 8.3 in, I would go with a MECHANICALLY injected International DT-466. They can be had off Ebay very cheaply. They have replaceable liners and are infinitely rebuildable and capable of serious horse power if thats what you want/need. And complete rebuild kits are available for the DT-466 inexpensively On-Line.
AND you can avoid the evil and expensive Cummins dealer. I really dislike those guys. I would go with this instead of the stock and much over rated Cummins 5.9L. The weight difference isnt a whole lot for a vehicle meant to haul 71 people.
Some firewall alteration might be needed but thats what bi-metal jigsaw blades are made for.

Get an olde Ford or Chevy VAN engine cover to dress it up a bit and cover that valve cover that will be sticking inside a bit. Take a weekend at most.
You might also want to see about the front end, an extra leaf on the springs to help support the extra 1000lbs that will be residing up there 24/7.

You might want to consider an Eaton manual transmission.

They are cheap when rebuilt and indestructable...literally, in a schoolbus. You couldnt kill one if you tried.
Even a used one that isnt any good for Semi any more will last another 20 years in a skoolie without rebuild.
Put 5 gallons of clean synthetic oil in it and go. The junkyards are full of them.

Something like a RTO9513. Thats thirteen gears. VERY helpful to gradually put beaucoup ponies to the ground without stressing anything unduly. Gently on the throttle. No reason to over-rev and then...skip shift.
Truckers skip shift when empty so as to get quickly up to speed and not over-rev a $30K engine.
A gear for every season or reason.

An RTO9513 ( bread and butter, industry standard) can be purchased (rebuilt) CHEAPLY from almost any truck transmission dealer.
This is a BULLET proof transmission and will last something like a thousand years more or less in a schoolie.

You also dont have to hit everygear. Skip-shifting is very common where every other gear is hit for just a brief bit til you're
up to speed.
The RTO9513 has a final gear ratio 0.68 - 0.75:1 thats Over Drive and give those that desire it an extra 10 +mph on the highway....always nice. AND as an added bonus, with tire chains, you could plow the lower forty with it! ! !

A small amount of air for shifting Hi-Lo range will be necessary; just a little bit, not much.

On my skoolie...which, did I mention, is for sale....

I have a small (Ebay) 12V air horn compressor that also powers my Big Rig air seat and provides compressed air to the Spinner II oil cleaning centrifuge.

With the spinner II, oil changes no longer need take place.

This makes using synthetic lubrication affordable as the oil is never thrown away, and makes those expensive engines last SO much longer. UPS etc has been using them for about 20 years now as well as many other penny pinching folks.
The Spinner II can be had (used) cheaply on ebay.

Much can be done mechanically with a skoolie when borrowed properly from their big brothers on the highway.....
cheers, Bob

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Old 09-20-2011, 10:06 AM   #42
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Join Date: May 2010
Posts: 59
Re: Whose getting 10+ mpg and what engine is it?

Bob are you located anywhere near southern WI or Northern IL by any chance? I could use some wit and you sound like the man
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Old 09-21-2011, 01:10 PM   #43
Join Date: Jul 2009
Posts: 46
Year: 1987
Coachwork: International
Chassis: International
Engine: International 6.9L diesel
Rated Cap: 71
Re: Whose getting 10+ mpg and what engine is it?

[quote="newtoskool"]Bob are you located anywhere near southern WI or Northern IL by any chance? I could use some wit and you sound like the man[/quote

"home" is small town near St.Louis, MO.

I just LOVE the folks who "swear" they got 20+mpg in a vehicle that weighs about 15-20,000 pounds empty.

I'm lucky to get 20-22 mpg in my small Nissan pickup w/four cylinder engine and five speed O.D. that weighs about 1/5
of the afformentioned skoolie, has a total frontal wind resistance about 1/4 of the skoolie.
Also there is a lot of induced drag that is generated by the skoolie's large flat rear end, similar to that generated by a semi.

While diesel contains more BTU's (energy) per gallon than gasoline, and so more mpg, a large vehicle is only going to be
able to put only SO much of that energy to the ground in the form of forward motion.
The rest is just friction and other forms of HEAT.

The modern engines using super-synthetic lubricates such as Royal Purple,( which is the best! ! !) have decreased internal friction markedly.

FRONTAL Wind resistance has also been lowered increadibly.

You might want to check out the LATEST advance in decreasing wind resistance on a large vehicle.....AirTabs.
These are applied to the surface of many Big Rigs.
Air Tabs reduce the turbulence and "induced drag" behind a large (square) vehicle.
They would work wonders for a skoolie to.

I was once driving a brand new International / Navistar "Eagle" class C rig in 1997.
It was completely tricked out with bunk beds and all the bells and current Freightliner has fridge and microwave too. I really like to rough-it.

Anyhow, the 1997 International had a Caterpillar engine and onboard computer that CONTINUOUSLY displayed the
exact fuel milage we (partner and I) were experiencing every couple seconds.
It was a daily game, to see who could maintain the best fuel milaegae for the longest time based on the contiuous
computer output. it was HARD, as the slightest pressure on the throttle would cause it to drop. Slight dips and rises in the road would cause it to fluctuate greatly. A slow, low rise in the road and down it would plunge.
The auto-pilot (cruise control) helped quite a bit but had to be set just so.
A single mph too high and DOWN the mpg would shoot according to the computer.
As an Owner Operator, I'm not sure I'd want THAT particular option these days.
A bad day in the mountains would give me an ulcer.

My partner and I had a very LOW PROFILE load as we were pulling a spread axle flatbed that would LEGALLY handle 55K pounds.
Our load was roofing supplies....shingles. Not as good as flat steel but better than bricks.
We had VERY litle wind resistance as we had the load tarped.
The BEST we were able to get was on Interstate 95 in the Georgia Flatlands and bounced around 7 +/-mpg.
And THAT is if the computer could be trusted.
That was the state of technology at that time.

Truckers are no different than skoolies. There is ALWAYS some guy that swears his rig is "Dialed In" just right and makes claims that would make the sales folks proud and engineers blush.

I've done better than take it all with a grain of salt...I've discovered a secret of my own....Its called a Salt Lick block. I tell you I had a skoolie for sale????
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Old 11-11-2011, 11:59 AM   #44
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Join Date: Sep 2010
Location: Ocala, FL
Posts: 613
Year: 1995
Coachwork: Bookmobile body by Farber
Chassis: International 3800
Engine: Navistar DT466/Alison MT643
Rated Cap: 1
Re: Whose getting 10+ mpg and what engine is it?

I bought recently a 1995 International 3800 bookmobile. I drove it from TN to FL about 700 miles and calculated the fuel economy at 10.3 MPG (2nd leg, 317 miles, 30.826 gallons), averaging about 50 MPH on the interstate (it has a bit of a balance issue, so I couldn't drive faster).

It has a DT466 engine with 150,000 miles and an Allison MT643 transmission. Total weight was somewhere around 20,000 pounds.
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Old 08-17-2012, 01:48 PM   #45
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Join Date: Aug 2012
Posts: 9
Year: 1991
Coachwork: Bluebird
Engine: 5.9 Cummins
Re: Whose getting 10+ mpg and what engine is it?

another 5.6 cummins on a '91 bluebird tc2000 getting 10+ mpg. when i bought the bus the school mechanics told me to add a quart of oil (any clean oil but not transmission) to every fill. this was because the diesel got too dry when the sulphur ratio was lowered at the pumps and they began having engine troubles with their fleet. the suppliers tried selling them fuel additives but nothing worked and was more expensive too. both the owner of the fleet and a mechanic in his shop individually pressed this point home to me if I wanted my engine to last. I don't know, but it seems to affect my mileage in the right direction as well.
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