MAB3L, the most reasonable truck on the road!

[superj]

My best is 23mpg also but it was mixed driving

 

[bhgl]

My best is 23mpg also but it was mixed driving

Dang, 23 MpG from mixed driving...

This is why I do kind of wish I had the motivation to install a manual, but I'm genuinely exhausted just thinking about the conversion.

It would pretty easily be the single biggest improvement I could make. Maybe if I come upon a ton of free-time and a butt load of money.

 

[pentode]

FWIW the last time I did any mileage runs I got 22-23 in mixed/around town and 24-25 at (slow) highway speeds. I have a very light foot though as I got my lifetime supply of speeding tickets before I was 20.

The way I drive, it seems to make almost no difference with this truck/engine/trans/rear end combo.

 

[bhgl]

FWIW the last time I did any mileage runs I got 22-23 in mixed/around town and 24-25 at (slow) highway speeds. I have a very light foot though as I got my lifetime supply of speeding tickets before I was 20.

The way I drive, it seems to make almost no difference with this truck/engine/trans/rear end combo.

Dang, 24-25 is really the top end of what people get on these trucks short of the 4 cylinder setups. Do you happen to know what ratio rear end you have?

If you drive with good fuel economy focused habits like coasting up to lights, gentle acceleration, e.t.c. I think this truck just sorta gets what it gets.

What are slow highway speeds for you? Typically I'm driving at speed limits posted at 90-100 KpH, occasionally 110. With some occasional slow downs to 60-70 when the highway passes through a town.

 

[pentode]

If you drive with good fuel economy focused habits like coasting up to lights, gentle acceleration, e.t.c. I think this truck just sorta gets what it gets.

What are slow highway speeds for you? Typically I'm driving at speed limits posted at 90-100 KpH, occasionally 110. With some occasional slow downs to 60-70 when the highway passes through a town.

I only get up to 110km/h when I have a lot of ground to cover On the stretches in NB where it's 110, I might drift up to 115 occasionally if I'm doing a multi hour trip but basically I'm rarely in that much of a hurry. I guess what I mean to say is I don't speed. When I go down to Maine, I get some 110-115 in in Canada and then a lot of the Maine part is 55mph so it evens out mileage wise.
Like you said, they seem to kind of get what they get. I was hoping to find ways to bump it up a bit but I don't put on enough miles these last several years to have it really add up.

 

[Blmpkn]

Dang, 24-25 is really the top end of what people get on these trucks short of the 4 cylinder setups. Do you happen to know what ratio rear end you have?

If you drive with good fuel economy focused habits like coasting up to lights, gentle acceleration, e.t.c. I think this truck just sorta gets what it gets.

What are slow highway speeds for you? Typically I'm driving at speed limits posted at 90-100 KpH, occasionally 110. With some occasional slow downs to 60-70 when the highway passes through a town.

There's only so much efficiency to be had with a vehicle that's "aerodynamicalness" is closer to being that of a peterbilt than it is a Honda civic. Literally. I got all nerdy and looked up drag coefficients and everything a few years back lol.

 

[pentode]

I've been banking heavily on the "Static Bubble" episode of Mythbusters... you know that one?
Banking in the sense of being cheap.

 

[pentode]

Dang, 24-25 is really the top end of what people get on these trucks short of the 4 cylinder setups. Do you happen to know what ratio rear end you have?

Sorry, somehow I missed that. Mine is an F6, which I believe is a 3.73 limited slip.

 

[pjtoledo]

The electric AC compressor is going to be a bit of a faff I'll say that now, but I'm in a similar situation to you where I only need AC for those specific times of year where the weather makes it absolutely essential.

As for the belt you will absolutely need to get a different length belt, your other option is you delete the AC is to put in a dummy pulley in its exact place to maintain the same tension which isn't the worst option, but is just less efficient and takes up much needed space.

In general, lower RPM typically does mean better fuel economy, but with our trucks and their tuning I've found that below 2500-2750 these trucks are tuned really poorly and dump fuel.

View attachment 112794
Based on this graph from Da Silva racing from a long time ago, on a mostly stock 3.0. As well as my own driving with a basic OBD2 scanner monitoring fuel volume. This graph is old, and I had to find a lot of the information about the vehicle by reading forum posts, but it's a 3.0 manual, with an indeterminate axle ratio, but combined with other graphs made for the 3.0 vulcan, it shows the fuel mixture leaning out around 2750-3000 just before/during the peak power band.

Generally speaking however I get my best results keeping the truck as low as possible within the given range of 2500-3000 RPM.

Out of the two options you listed, 2200 RPM is probably more efficient, but there's so many other variables you'll get a better answer from doing some fuel economy testing yourself.

If speeding isn't a concern for you, by going a few MpH faster you might actually see some improvement in fuel economy by raising your rpm to the lower side of that range.

actually, that graph says more fuel per unit of air is being used above 68 mph.

 

[sgtsandman]

My 2011 was supposed to get 23 with highway driving. I came close, once. Before I started doing things that hurt fuel mileage, I was seeing 21 - 22 mpg fairly regularly.

Now, 20 is a good day, with 19 being the average. 21 happens on occasion as long as the majority of the trip is relatively flat and stay around 55 - 60 mph but that is not a common thing with the terrain around here.

 

[bhgl]

I only get up to 110km/h when I have a lot of ground to cover On the stretches in NB where it's 110, I might drift up to 115 occasionally if I'm doing a multi hour trip but basically I'm rarely in that much of a hurry. I guess what I mean to say is I don't speed. When I go down to Maine, I get some 110-115 in in Canada and then a lot of the Maine part is 55mph so it evens out mileage wise.
Like you said, they seem to kind of get what they get. I was hoping to find ways to bump it up a bit but I don't put on enough miles these last several years to have it really add up.

Yeah it really all depends on how much you drive.

I'm on course to do just about 24 000 KMs this year, and probably every other year after that. Compared to what I was getting previously to now, and with that mileage and a cost of a litre at 1.70, I'm slated to save about 1000$ a year on gas. Here's hoping I can save more!

 

[bhgl]

actually, that graph says more fuel per unit of air is being used above 68 mph.

Ah shit you're absolutely right, that's the stoichiometric ratio. Thanks for letting me know so I can stop using that graph when I talk about fuel economy lol.

I know that on my handheld scanner I was getting less fuel volume at cruise between 2500-3000, compared to 1800-2500ish, I'm imagining a dyno-pull isn't going to give you an efficiency focused fuel curve.

I really need to just get something to log average fuel economy.

 

[bhgl]

Sorry, somehow I missed that. Mine is an F6, which I believe is a 3.73 limited slip.

Funny thing about that, and you may want to check, but that's actually what my door sticker said before I actually did the math/counted rotations and it turned out to be a 4.10 limited slip.

If it is a 3.73, that's probably why you're getting a better average fuel economy than I am at speed, we had a chat about axle ratios in a previous thread and it was generally agreed that 3.73 should net an improvement, but going lower may make the engine drop into a lower gear too often.

 

[pentode]

If I get out today I'll check my rpm at 100km/h and we can compare. Maybe not completely definitive but easier than jacking up my truck in the heat.

 

[bhgl]

If I get out today I'll check my rpm at 100km/h and we can compare. Maybe not completely definitive but easier than jacking up my truck in the heat.

Good idea, granted my truck is a bit of a frankenstein, with a weird ownership history on top of it, so my axle could've been swapped out at some point, or just built incorrectly from the factory lol.