Cummins vs Hummer Towing 6,000 lbs

RoyJ wrote:

nickthehunter wrote:

RoyJ wrote:

There're many studies showing the closer to the cab a 5th wheel sits (commercial semis), the less drag.
One extreme is euro semis, where the trailer is almost touching the cab fairing. Mercedes got 18 l/100km (13 mpg) at 88k lbs GVW.
The other extreme is stretched show trucks (300+ WB Petes), 5 mpg on a good day.
Best mileage would be a short box pickup with a sliding 5th wheel. Have the 5'er up tight against the cab on the hwy.

The cab of a semi is the same height as the trailer (they use wind deflectors on top of the tractor to ensure this). An RV fifth wheels sits way above the top of the pickup (usually much higher than a TT) and there is still a considerable gap; albeit less then a TT but it is not insignificant. Comparing semis to RV's is Apples and oranges.
It's the differential in height along with the gap that matters. The TT has more gap, the 5er has more height. And the answer to which matters more is anecdotal at best.

I wasn't comparing a semi to a pickup.

I was comparing 2 semis, 1 with larger gap, 1 with smaller. Then 2 pickups, 1 with larger gap (TT), 1 with smaller (5'er).

I do agree typical drag area is larger on a 5'er, but your Cd will be lower. Maybe not Cd*A, which depends on the size of the 5'er.

A short box slider 5'er may have a gap of 3', while a long box TT will have a gap of ~14' (8' box + 1' hitch + 5' a-arm). 3 vs 14 makes a difference.

Good job with the “editing”.
Now you changed from the same truck pulling different trailer to different trucks pulling different trailers - and hence can predict which setup will get better mileage; and it’s still anecdotal at best.

nickthehunter wrote:

RoyJ wrote:

There're many studies showing the closer to the cab a 5th wheel sits (commercial semis), the less drag.
One extreme is euro semis, where the trailer is almost touching the cab fairing. Mercedes got 18 l/100km (13 mpg) at 88k lbs GVW.
The other extreme is stretched show trucks (300+ WB Petes), 5 mpg on a good day.
Best mileage would be a short box pickup with a sliding 5th wheel. Have the 5'er up tight against the cab on the hwy.

The cab of a semi is the same height as the trailer (they use wind deflectors on top of the tractor to ensure this). An RV fifth wheels sits way above the top of the pickup (usually much higher than a TT) and there is still a considerable gap; albeit less then a TT but it is not insignificant. Comparing semis to RV's is Apples and oranges.
It's the differential in height along with the gap that matters. The TT has more gap, the 5er has more height. And the answer to which matters more is anecdotal at best.

I wasn't comparing a semi to a pickup.

I was comparing 2 semis, 1 with larger gap, 1 with smaller. Then 2 pickups, 1 with larger gap (TT), 1 with smaller (5'er).

I do agree typical drag area is larger on a 5'er, but your Cd will be lower. Maybe not Cd*A, which depends on the size of the 5'er.

A short box slider 5'er may have a gap of 3', while a long box TT will have a gap of ~14' (8' box + 1' hitch + 5' a-arm). 3 vs 14 makes a difference.

I only get 12mpg towing my 7,500# 23' Boat with my 01. That is mostly 70mph.

RCMAN46 wrote:
" Friend has a 13 RAM six speed stick with 3.42's his mileage is incredible." This statement is anecdotal at best. What is wrong with giving a mpg number?

He claims 26mpg communing 55 miles each way with most of the time doing 60 on I-5.

Me Again wrote:

FishOnOne wrote:
Summary towing a measly 6,000 lb camper:

Hummer: ~128 mile towing range (Epic Fail), Price $114k

Ram/Cummins: 9.7 mpg (Fail), Price $68k


Summary: No earth shattering news on the EV, but what was surprising was the underperforming cummins with a disappointing 9.7mpg towing this small camper that has a aero front end.

Link

That is NOT a aero front end! I has hard right angle corners, and the side wall seams appears a raise area along the front wall. All mileage killers like many cheaper RV trailers.

You would think towing a center console bay boat would be pretty aero but they're not.

dodge guy wrote:
Believe it or not this little air deflector gained me .5mpg towing my TT. It helped get the air up and over the front of the trailer. The absence of dead bugs on the front of the TT proved that.

That deflector preventing bugs on the TT is probably worth it's weight in gold.

Believe it or not this little air deflector gained me .5mpg towing my TT. It helped get the air up and over the front of the trailer. The absence of dead bugs on the front of the TT proved that.

" Friend has a 13 RAM six speed stick with 3.42's his mileage is incredible." This statement is anecdotal at best. What is wrong with giving a mpg number?

An air bubble is created behind the cab when towing a 5er. Put a basketball in the bed or a lawn chair and see what happens. Heck a big poop tote will rise from the bed.

Fisherman wrote:

bucky wrote:
18 mpg towing a 5er? Must have been the new Mattel model.

Time to see the eye doctor, I didn't say a 5er, it was a 5K lb.

Reading comprehension is a big part of understanding a topic. ;)