Engine/Transmission (1998.5 - 2002) V10 vs I-6 MPG Wishful Thinking

[Big Dawg]

Wade:



I can't speak about the cooling aspect but sometimes I will coast, roll or whatever you wanna call it it to maximize my fuel savings. Sometimes it may be more advantageous to coast, roll or whatever out of gear depending on whatever particular driving scenario you are in at the time. Again I am referring to a manual transmission. Perhaps somebody more knowledgeable than me can address this cooling situation but my gut feeling is that there is no effect.

 

[GMocanu]

Now, since changing to Amsoil, I usually coast out of gear down the last half of my street into my driveway. It's part of my cool down for the turbo.

 

[KMeek]

Had a 98 V-10 also. In town about 10 mpg. Highway driving highway speeds about 13-14. Could get 16 if you drove 55-60. Towing 5th wheel at about 7,000 pounds got 6-8 mpg. Same 5th wheel with Cummins is 10-13 mpg. In town or on highway empty about 17-18. The cummins is 5 times more fun to drive. It is inconceivable to me that anyone would get 16 mpg with a V-10 with combined city/highway driving.

 

[jponder]

I see what your saying big dawg. You are judt driving right, ie letting the engine slow you where avail and not wearing your brakes out. I do that also.

 

[dslmacdown]

Originally posted by jponder

I see what your saying big dawg. You are judt driving right, ie letting the engine slow you where avail and not wearing your brakes out. I do that also.

I downshift and coast in gear all the time I believe this saves on the brakes big time. My dad has a '91 Mitsubishi truck with a 5 speed and with coasting and downshifting he is still on the orginial brakes and clutch at 128,000 miles!!



MAC

 

[Scrappy]

in gear coasting

There is always fuel being burned if the engine is running whether in gear coasting or not. In gear coasting uses about the same amount of fuel as idling the engine, it only looks like less fuel is being used because the truck is moving.

 

[WadePatton]

you can't COAST --IN GEAR!

Unless you fully depress the clutch.



Some dictionary for "coast"-to continue to move on acquired momentum. to progress with little or no effort.



If the engine in pushing the drivetrain (as when you hit the loud pedal) or the drivetrain is pushing the engineas when you LET OFF the loud pedal, you are not coasting.



Another way to consider it. If the engine speed is in any way related to road speed, you are not coasting. Coasting is as if the engine was turned off. Which I used to do before I got this hydro-controls situation.



Still confused? (Autos don't apply) Go find a hill that's long but not too curvey. Start down it at say 50mph or reasonable and then LIFT. (Lift is an old road racing term for taking your foot off the throttle. ) If the hill is steep enough you will maintain some sort of progress to the bottom. This is NOT coasting because the driveline is turning the engine and therefore slowing you down.



NOW take that same hill and begin the test again, but shift out of gear and release the clutch. Notice how the truck "flows freely" down the hill and you pick up speed--NOW THAT'S COASTING!



COASTING, free from restriction by definition. Fun Fast and Illegal is places.



Yes, either way -taking your foot off the FOOTFEED will increase your MPG figures.

 

[jponder]

Originally posted by Pit Bull

Only have 11,000 miles on my 2002 3500RC 4x4 ETH/DEE with 3. 55's but I don't think I am close to having it broken in. I never tow or haul much and the mileage is improving. I am now getting 18 mpg around town. But last week I drove on the highway for most of 200 miles doing in the 70+ mph range and only got 16 mpg. I thought I was going to get 20+ My truck weighs 7000 lbs with me in it, and I know that even the wind can make a difference. But I expect this truck to get 20 mpg combined summer and 18 mpg combined winter after it get 20K miles on the it. Think I am realistic?

I was getting numbers like that at first. then they just started getting better and better

 

[Pit Bull]

Originally posted by jponder

I was getting numbers like that at first. then they just started getting better and better

I hope mine also get better, but I have a feeling that it will be when my truck gets over 30K miles before that happens.

 

[kebees4]

I have never got above 18. 5 miles per gallon empty. It now has 44,000 miles on it and when it was new it got same milage as it gets now. When I tow a 1500 lb. boat or a trailer with 3

4 wheelers on it it will only get 15-16 miles per gallon. It is stock and has never seen better than that for mileage. I have been on 3 trips 500 miles one way using cruise. I have been disapointed with the mileage I have gotten from my truck.

 

[John Berger]

I've kept a log for the last couple of years and my mileage varies from 14. 5 to 16. 5 unloaded. I have got in the high 18's, and that was on the highway running 58-60 mph. Compared to other posts in this thread, my numbers are low. I tend to blame that on the driver. When I tow, I usually get between 10 and 12 mpg, again depending upon how fast I go. I'll be making a trip to Texas at the end of this month. It will be the first really long trip with the 5'ver. By long I mean over a thousand miles one way. It will be interesting to see what kind of mileage I get on this trip.

 

[jponder]

Originally posted by John Berger

I've kept a log for the last couple of years and my mileage varies from 14. 5 to 16. 5 unloaded. I have got in the high 18's, and that was on the highway running 58-60 mph. Compared to other posts in this thread, my numbers are low. I tend to blame that on the driver. When I tow, I usually get between 10 and 12 mpg, again depending upon how fast I go. I'll be making a trip to Texas at the end of this month. It will be the first really long trip with the 5'ver. By long I mean over a thousand miles one way. It will be interesting to see what kind of mileage I get on this trip.

I have noticed that the mileage of the 2001 HO seems to run high. I know of a couple of people who can bang out some 24+ MPG going the same speed you are talking about. I dont know why but it seems the 2001. 5 might be lower.

 

[Big Dawg]

jvanwaardhuizen



There is always fuel being burned if the engine is running whether in gear coasting or not. In gear coasting uses about the same amount of fuel as idling the engine, it only looks like less fuel is being used because the truck is moving.

I disagree...



My manual transmission truck uses no fuel coasting in gear... that is until it gets to the point where the RPM drops to the point where the engine is about to stall (about 800 rpm or so) and then fuel is injected into the motor to keep it running.



If someone can prove to me otherwise I'll admit to being wrong in this thread. I'm not too big for that.

WadePatton





you can't COAST --IN GEAR!

Unless you fully depress the clutch.



Some dictionary for "coast"-to continue to move on acquired momentum. to progress with little or no effort.

Wade... When my truck is coasting in gear, my truck DOES continue to move forward on aquired momentum with no effort.





I'm not trying to start a flame war but will stick with what I said.

 

[dslmacdown]

I know in a modern fuel injected car, the fuel system shuts off the injectors when coasting in gear. I have seen it, driving with a scan tool, cruising down the road and lift off the pedal. The injector pulse width (injector on-time in milli. sec. ) goes to 0 and the O2 sensor reads lean. Just me $. 02



MAC

 

[hammersley]

Uses no fuel????

Help me - but if the motor is running - she is using fuel! And remember at idle the motor will consume the least amount of fuel BUT the MPG is the worst that you'll ever see - which is ZERO!

 

[Pit Bull]

Re: Uses no fuel????

Originally posted by hammersley

Help me - but if the motor is running - she is using fuel!

Logic, don't you just hate it. :-laf

 

[Turbo Tim 1]

I am at work so I can't do it, but will someone please go out on the road and coast from say 60 down to 20 mph. Then do it again only this time turn you key off. Is there any difference? Other than it's harder to steer and stop.



Originally posted by hammersley

Help me - but if the motor is running - she is using fuel!



Who say's it's running? The only thing I know for certain is that it is turning. Just my useless 2 cents

 

[jponder]

What big Dawg is saying might be right. I dont think it is really coasting but if it shuts off all fuel then that is a great way to really cool off the engine. I did it today. I got to the point where I always slide into neutral and I just left it in high and got off the pedal. I did slow considerably fatser but heh I got to stop anyway. I will probably do that a little more in the future. I bet you will really cool that turbo down using in gear engine braking plus youll save alot of brake pads.

 

[hammersley]

Shutting her off?

I guess I didn't get it - are you actually shutting her off and DEAD Coasting?

 

[jponder]

Re: Shutting her off?

Originally posted by hammersley

I guess I didn't get it - are you actually shutting her off and DEAD Coasting?

Yes hes using engine braking alot, its got its advantages . its not coasting but it does some things coasting cant do