Uphill MPG and speed

[mandolindave]

I just have, average MPG info, on the readout on my tow vehicle, not real time MPG info.

So…I zero out my MPG, to make it easier to find the sweet spot as far as what speed to travel up hill. I am not sure if this does the drivetrain any favors but it does help gas mileage. I am really more concerned with wear and tear, than MPG.

I determined that I can get at least 2 more MPG, when I dropped from 65 to 55, on normal terrain.

My question is, how fast do you tow, going up a steep grade mountain pass

[mojo]

No offense to you on this thread, but there seems to be a lot of micromanaging of MPG on the forums when towing. And with all the factors of headwinds and tailwinds, mountains and downhills, traffic and road conditions, all constantly changing...I just don't see the value when out for a good time.

But to answer your question, my eyes are focused on the trans and engine temp gauges when transcending steep grades. My MPG planning revolves around Gas Buddy and finding the difference in the price of gas which can very from 50¢ or more between towns.

[DuncanK1]

You did NOT answer the question which was "How fast do you tow, going up a steep grade". No offense!

[SSquared]

Like mojo, my first concerns are the engine and tranny temps.

On another internet forum, someone said that for my model vehicle, the transmission will not lock up in first or second gear, so climbing in third means less heat and less wear. So I like it when a climb is gentle enough that I can keep it in third. That means about 45mph or faster.

As a practical matter, mountain climbs are usually limited by grade, road condition, and traffic.

Foot on the floor in second gear, my trip computer's instantaneous read-out says 2 mpg.

[KJRitchie]

I haven't driven out west yet with my 2008 Classic 25fb/2010 Tundra DC 5.7 2wd but on some hills in Arkansas I usually tow at 60 and try to go up the hills at 55 to 60mph. I manually shift the transmission. 3rd gear is where the rpms are for max torque on this engine. If the speed starts to not hold in 4th and before I have to mash the pedal all the way down I shift manually down. The transmission temperature and coolant gauges don't seem to budge. From the instantaneous mpg readout the mpg is low so I hope on the other side of the hill I can shift up and recover some mpg.

Kelvin

[DuncanK1]

In answer to MandolinDave....You go a lot of different speeds!

I used to drive loaded trucks across Europe - all with manual shift. Germany is all ups and downs. Switzerland just seems to be all ups!

Use any down inclines to gradually build up speed and momentum but don't go mad - you need these times to rest the engine and cool.

On the uphill gradually come off the gas trying to keep it at whatever comfortable RPM range your truck does - maybe 2500-2750? Eventually the mountain will win and you need to downshift the gears to keep high enough revs. You may even have to go to 1st or 2nd. If you can keep it in 3rd or 4th at 2500-3000 then just enjoy.

With an auto its a matter of keeping at the sweet spot of about 2750 RPM.

I think by doing this kind of strategy you will be kind to your engine AND get the best mileage for the gas tank?
I do agree you need to watch the temp and oil like a hawk.

Also, there is a simple matter of physics. If you use a lot of gas going up then hopefully you can gain free stuff on the other side. Resist the temptation to go too fast downhill. You will just waste energy braking at curves plus remember you take 2x as long to stop going downhill. Just coast - and of course ENJOY!

[paiceman]

We generally tow the speed limit up and down hills, especially on interstates. On two lanes we drop down a bit due mainly to hauling 9,000 pounds behind us - turns and all. As to MPG we budget based on our fuel usage over the last trip. Last trip 5,500 miles, average usage 13.7 MPG. If we use a little more or a little less that is fine as we always budget for high usage. In other words, last trip was 13.7 MPG, I figure 12.7 for pre trip budgeting. We do the same for campgrounds, always budget for high cost and hopefully come in under. That said, I agree with MoJo, we do this for fun, i'ts "our time", and a few MPG here and there are only going to impact us if Diesel goes way up in price. By way up I mean over $5.00 per gallon. If we get the 13.7 MPG, for 5,000 miles at $3.00 per gallon our fuel costs are $1,095, if $5.00 per gallon our costs are $1,825.00. We will simply cut some things out to make up the $730.00 difference or spend less while at home. Our F350 6.7 Diesel pulls up hill at just about any speed I want, but as noted we stay within the speed limits or a little under.

Enjoy

Bud

[mojo]

Originally Posted by DuncanK1

You did NOT answer the question which was "How fast do you tow, going up a steep grade". No offense!

Between 35 and 65 depending on conditions...close enough?

[DuncanK1]

We agree!

[Bill M.]

Made the mistake of coming out of Grey Bull headed east without filling up or really checking fuel. I can tell you for that grade I pulled at about 40 mph and was getting 6 mpg. (Diesel). We made it but I was worried enough to check milage and decide whether I need to keep on or turn around. On the highway I pull at about 63 and sometime slow to 60 if it will keep it in overdrive. We get about 14-15 average mpg.

[RangerJay]

Like others have said - it's not the speed that is important - it is how much work you're putting on the engine and transmission - my measure is the temperature gauge not the speedometer - serious grades mean slowing down, gearing down - and climbing at a rate that feels comfortable - if someone behind me feels I'm travelling a little too slow - well - they are free to pass or just relax and cool their jets till we both get to the top .....

Should also point out that hilly terrain does not make a great difference in gas mileage - it is headwinds or tailwinds that creates big additional costs or savings.


Jay

[gator.bigfoot]

I will always slow down. First I kick it into 5th or 4th part way up and then slow down gradually from 65 to as slow as 50 if I have to. It is more of a "feel" and sound of the engine that determines how much I slow down. I can keep the cruise on and it will go up fine on its own at 65, but it really kills the MPG. So if I control it I can usually get a decent number at the end of the day (14 or better). Otherwise it is around 12.5 MPG. Maybe not enough to get exited about on short trips but on longer trips it can add up. Again fuel economy really depends on grade and wind direction. Sometimes no matter what I do the fuel economy is still poor.

[reelfastgreg]

i go uphill at the posted speed limit. i don't have time to check MPG as usually these are pretty twisted roadways. perhaps your question would have better relevance if you considered the % of the grade. most interstates are pretty flat, rarely exceeding 6%.

[mandolindave]

A friend of mine, simply keeps the gas peddle in the same position that it is in, as when he is going 65 on a flat stretch.

[slowmover]

I may hit the grade harder than my normal travel speed. Suspend the cruise control. I expect to fall back in speed depending on ascent percentage and distance. As well at least one gear on the manual transmission.

Ascent speed is relatively meaningless. It is the descent that matters. I can hardly see a good reason to arrive at the top and to have to slow for the proper descent speed. Chances are that I am already near to that speed as well as the proper gear with above way of doing things.

I will say that anyone using CC on a steep ascent is none too bright. The speed differential between vehicles widens. Nothing quite so stupid as four wheelers piling up behind slower vehicles.

Separation distance is just possibly MORE important now than ever.

As to fuel burn, there is no good reason, again, to ask the motor for more than is needed. Speed matters not, but braking and evasion distance does. Fuel burn, thus temps, will take care of themselves when emphasizing defensive driving on an ascent . . the all important descent is just ahead.

[Lara Me]

I do the speed limit or 5 over, up to 65 mph. With a Cummins diesel, power is not a problem and the revs rarely exceed 2000rpm. A really long pass with a steep grade will make the oil and transmission temps creep up a tad, but never in unfavorable ranges. Gas mileage suffers, but it is usually redeemed on the downhill run, using exhaust brake to help regulate speed.

Most often I am passing tractor trailers and gas powered RV's.

[Jack46]

With our earlier 2008 Suburban 2500 we generally traveled at 65 mph on the flats and experienced about 10 mpg. In the hills we kept the rpm's below 3000 and whatever gear was needed. More than once out west we experienced a 1st gear climb at about 4 mpg. I don't think you indicated what your tv is, but gassers really suffer at higher altitude. I'm told a horsepower loss of 3% per 1,000 feet in altitude.

All this is said given the fact that we recently got rid of the 'Burb in favor of a Silverado 2500 HD Duramax. We expect a much better driving season - rpm's, mph, and mpg - this year

[SuperTrouper]

I manage the speed limit (55-60) until my Pyrometer reaches 1000 degrees then I manage gear and speed to keep the exhaust gases under 1100 degrees and Tranny oil temp under 200. (2002 7.3 powerstroke with DPTuner +80HP, 15,000 lbs GW trailer and truck). I can usually hold 50 easily but tend to go a little slower if trucks in the granny gear lane are going under 30. I don't like traveling in adjacent lanes at more than a 20MPH differential as trucks can sometimes pop over a lane to avoid losing inertia when coming up on a heavily laden 10MPH truck and if you are barreling up the hill in an adjacent lane you won't have a lot of time to react. An extra 15-20 minutes to make the grade so to speak never hurt anyone and you need to slow down going down the other side anyway.


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[NateS]

I tow at 60, and on a 2:45 hour drive from Pasadena to Central coast of California I average 18 mpg. Its 18.5 until the climb between Santa Barbara and Buellton. I tow the climb at 60 in 5th gear. The temps don't budge on our 2014 VW Touareg TDI. I'm able to tow it at 65, same gear but then I miss the scenery

[tyggeln]

I tow at 55 which is the law in CA for vehicles while towing; uphill on gentle climbs on intersates I try to maintain 55 but realize the mountain wins and its important to watch the transmission oil temp and coolant temp. Going over passes near 9600' I end up just crawling up the hill above 8000' in first gear - like on Sonora Pass in CA. On the other side controlling the rig speed without using brakes and so I'll be in 1st gear and top out about 20 - the turns also don't allow me much speed either.

Interestingly, although the physics says I should make up the poor gas mileage on the downslope, the mpg in the computer never recovers after going through a pass. Some kind of paradox that's probably explainable with a look into the math...