MPG doubled on manual over automatic???

FloridaCliff · June 22, 2009, 08:41:02 AM

I agree with Jack that you will probably only see a 1-1.5 mpg gain based solely on the transmission.

Most agree that the biggest factor is your right foot.

It has been discussed here many times by different posters on the gains seen based on speed driven.

I think for most, the automatic with a lite foot is the way to go.

Though I personally enjoy shifting.

Cliff

Garymci5 · June 22, 2009, 08:57:02 AM

Our old Eagle 05 (40' x 8V71N x 4spd manual) got about 5.5-6.5 MPG, empty at 30K lbs and a smidge less towing fully loaded at over 37K lbs. This was about 30-40% less than my 35' GMC Fishbowl with a 2spd auto and 6cyl.

The 'new' MCI challenger (35' x 8V71N x 4 spd manual) has a log book showing high 7's to low 9's. Same owner for over 30yrs, same trip every year, same trailer.

Hopefully by not towing, and the addition of synthetic engine oil, running 60-65MPG, she'll provide a consistent 8.0+MPG or better, unless running the hills alot. The gearing is a bit short for highway blasting but works well for hills.

I broke my promise that the "next" bus would have an auto and turbo engine, at least it has power steering-- which makes shifting and turning MUCH easier.

In a round about way this might help.....

RJ · June 22, 2009, 10:36:56 PM

Quote from: Garymci5 on June 22, 2009, 08:57:02 AM

. . . and the addition of synthetic engine oil, running 60-65MPG, she'll provide a consistent 8.0+MPG or better. . .

Gary -

Be careful here. Detroit doesn't recommend running multi-weight oil in the two-stroke diesels, and the vast majority of synthetics on the market are multi-weight - how many of them are CF-2 or even CF-4 rated???

The ONLY straight 40wt synthetic that I'm aware of that comes close to meeting DDA's 2-stroke specs is made by Royal Purple.

You might want to compare the price of seven gallons of synthetic vs seven gallons of dino, and pencil out whether or not a slight increase in fuel economy can/will justify the difference in cost between the two oil types over the life of a single DDA-recommended oil change period. Oh, and don't forget to factor in the additional oil you might need to keep the level correct between changes, too.

If you decide to stick to dino oil, remember DDA recommends using just straight 40wt, CF-2 oil with a 1% or less sulfated ash content in the two-stroke engine.

FWIW & HTH. . .

Now back to our regularly-scheduled fuel mileage discussion. . .

Garymci5 · June 23, 2009, 12:57:33 AM

RJ-

While I appreciate the good intentions of looking out for a fellow bus nut, in lieu of another thorough explanation of "why", feel free to spend a little time getting acquainted with the answer (it does a much better job than I at this time of night):

https://www.amsoil.com/storefront/ame.aspx

Garymci5 · June 23, 2009, 06:53:58 AM

http://www.axlealliance.com/pdf/vocations/Lube-Oil-Fuel-Requirements.pdf

This has a ton of useful tech info about oil and fuel for Detroit Diesel.

....now back to the real subject at hand.....

MCI-RICK · June 23, 2009, 07:42:39 AM

Gary,

Great link on oil as per Detroit Diesel. It's good to have info from the manufacturer and their say on additives. Although, I know Lucas oil is a commonly used additive by busnuts and truckers. Does it help or hurt is a subject I think will never be settled.

The 40wt oil can be purchased from Napa and others but I've never seen 50wt anywhere. Might be good to boost the 40wt with some 50wt after a couple thousand miles.

Rick

RJ · June 23, 2009, 08:30:18 AM

Gary -

I don't want to hijack this thread any more than it already has been, so please take a look at the new thread I will be posting later on tonight.

FWIW & HTH. . .

kingfa39 · June 24, 2009, 06:18:14 PM

i cant speak for any other bus, ours is a 4106, we drove it from lexington NC to california and back again, towed a car and i drive fast when traffic conditions allow, i had the 4 speed manuel transmission, the bus got 10+ mpg on every check both directions. wife wanted a automatic so she could drive, had it put in , did not change anything else v 730 shifts great never had any trouble, but the truth is the bus now gets 7 mpg and you have to keep a close eye on the engine temp , never got over 180 on the calif trip even on long climbs, i am now hesitant to climb long climbs. also the top speed is reduced to 76 mph as opposed to better than 80, i dont mind that because i dont care to drive that fast but thats one reason for the reduced mpg. the transmission final gear is not the same. This is the experience i had, i would never change over a 4106 if i had to do it again.
Frank Allen

Garymci5 · June 24, 2009, 11:27:07 PM

Quote from: kingfa39 on June 24, 2009, 06:18:14 PM
i cant speak for any other bus, ours is a 4106, we drove it from lexington NC to california and back again, towed a car and i drive fast when traffic conditions allow, i had the 4 speed manuel transmission, the bus got 10+ mpg on every check both directions. wife wanted a automatic so she could drive, had it put in , did not change anything else v 730 shifts great never had any trouble, but the truth is the bus now gets 7 mpg and you have to keep a close eye on the engine temp , never got over 180 on the calif trip even on long climbs, i am now hesitant to climb long climbs. also the top speed is reduced to 76 mph as opposed to better than 80, i dont mind that because i dont care to drive that fast but thats one reason for the reduced mpg. the transmission final gear is not the same. This is the experience i had, i would never change over a 4106 if i had to do it again.
Frank Allen

Frank,

I think your story is the most concrete and semi-scientific for comparing the two transmissions and effects on MPG. FWIW, sorry to hear of the huge drop in MPG; diesel isn't a $1.35 anymore (sniff). It might be worth replacing the ATF with full synthetic to help internal effeciency and lower the heat exchanger (oil/coolant) temperature. Naturally it'd last longer, too. I'd also put in a good word for something like Redline Water Wetter to help reduce coolant temps. Lastly, the trans should be locked up in direct or over-drive. Not doing so would drastically lower MPG and raise RPM some when throttling on.

I'm a big fan of both Redline and Amsoil products. Not cheap, but well worth it IMHO.

No doubt the reduced gearing makes some difference. If she's good on the hills one could decrease the axle ratio, if something was available and appropriate for your needs.