GM I6 Diesel Impressions

[Storm56]

This thread is about the 1/2 ton Chev 3.0 inline 6 cylinder diesel, not heavy duty trucks towing heavy loads.

Absolutely the diesel rules in those heavy duty applications. 1/2 ton pickups much more debateable.

 

[Hay Dude]

This thread is about the 1/2 ton Chev 3.0 inline 6 cylinder diesel, not heavy duty trucks towing heavy loads.

Absolutely the diesel rules in those heavy duty applications. 1/2 ton pickups much more debateable.

We know that, but the original post by the author of the thread discussed diesels, too. That generally opens the discussion up to anything related to what he discussed in the first post, wouldnt it?

 

[Storm56]

We know that, but the original post by the author of the thread discussed diesels, too. That generally opens the discussion up to anything related to what he discussed in the first post, wouldnt it?

Not my thread, but IMHO, the OP was specifically talking about the Chev 1/2 ton 3.0 diesel. To my way of thinking that would rule out the heavy duty stuff.

In no way am I trying to be argumentative. The only similarity between the 3.0 Duramax 1500 and a 3500 6.6 Duramax is that they are both diesel of course and GM. Completely different horses.

 

[Hay Dude]

Not my thread, but IMHO, the OP was specifically talking about the Chev 1/2 ton 3.0 diesel. To my way of thinking that would rule out the heavy duty stuff.

In no way am I trying to be argumentative. The only similarity between the 3.0 Duramax 1500 and a 3500 6.6 Duramax is that they are both diesel of course and GM. Completely different horses.

All good. These threads wander around. Even the OPs will take threads in other directions.

 

[s219]

This particular engine in the Chevy/GMC half-tons is pretty down on towing capability, and it's due to thermal management according to a GM engineer I talked to. In order to get the good efficiency, they were very careful with thermal loads and under hood heat management. There are some very specific decisions they made with under hood arrangement, insulation, foil shielding, etc. He said they planned to revisit that to increase the tow rating, and that is already underway from the sounds of it. It will likely come with a reduction in the fuel efficiency. Be curious to see if this is done across the board, or as part of an optional diesel max-tow package (as I expect).

I found that in the GMC lineup, the 5.3L has the best ratings for towing and cargo capacity. The 6.2L loses some of both because it is so much heavier (specs as 440# heavier curb weight, which seems hard to believe). The diesel is better than the 6.2L for cargo capacity, but 100# worse for tow rating.

 

[Hay Dude]

This particular engine in the Chevy/GMC half-tons is pretty down on towing capability, and it's due to thermal management according to a GM engineer I talked to. In order to get the good efficiency, they were very careful with thermal loads and under hood heat management. There are some very specific decisions they made with under hood arrangement, insulation, foil shielding, etc. He said they planned to revisit that to increase the tow rating, and that is already underway from the sounds of it. It will likely come with a reduction in the fuel efficiency. Be curious to see if this is done across the board, or as part of an optional diesel max-tow package (as I expect).

I found that in the GMC lineup, the 5.3L has the best ratings for towing and cargo capacity. The 6.2L loses some of both because it is so much heavier (specs as 440# heavier curb weight, which seems hard to believe). The diesel is better than the 6.2L for cargo capacity, but 100# worse for tow rating.

View attachment 655118

It’s funny how some seemingly unimportant parameter can be exceeded and render lower towing ratings. Wanted to buy a Jeep Gladiator Rubicon Diesel next year and preliminary towing ratings are slightly lower than gas. Now I know few people will tow heavy trailer with a Jeep Gladiator, but it still seemed strange.
I dug a little on the topic and found out the engine compartment couldn’t allow the Diesel engine to cool off enough to take advantage of its superior torque for towing, so they down rated its towing specs.

It is quite revealing to see how a 3L DIESEL has same specs as a gas engine double its displacement.
Diesel engines rock!

 

[lostcause]

Finally refilled after the trip when I brought my tractor back. 542 total miles on the trip meter this time, 22.26 gallons, average fuel economy of 24.4mpg. About 125 miles with 7k load, 145 miles with 2k empty trailer, and the rest with just me commuting. I tried watching the onboard meters as I went, but they aren't perfectly accurate. My best guess was around 25mpg with the empty trailer, and about 16mpg towing 7k - both at interstate speed limits. The rest was work commuting at speeds under 65mpg, which it likes better than 65+. As an FYI, the "best 50" mpg recorded on the dash meters so far is 33.3. Just under 3k miles on it now and I still love it. Tranny feels a little lurchy at takeoffs, but I'm sure I'll get to the point where I don't even notice in a while. during the summer months I do most of my commuting in an older car, so I won't get as many miles to evaluate it again until next winter.

Oh yeah, diesel down to $1.999 within 10 miles of my house. Cumulative economy after 6 tanks: 2860.7 miles at 27.7mpg

 

[Storm56]

Those are some impressive fuel mileage numbers for a full size truck!

 

[Hay Dude]

Finally refilled after the trip when I brought my tractor back. 542 total miles on the trip meter this time, 22.26 gallons, average fuel economy of 24.4mpg. About 125 miles with 7k load, 145 miles with 2k empty trailer, and the rest with just me commuting. I tried watching the onboard meters as I went, but they aren't perfectly accurate. My best guess was around 25mpg with the empty trailer, and about 16mpg towing 7k - both at interstate speed limits. The rest was work commuting at speeds under 65mpg, which it likes better than 65+. As an FYI, the "best 50" mpg recorded on the dash meters so far is 33.3. Just under 3k miles on it now and I still love it. Tranny feels a little lurchy at takeoffs, but I'm sure I'll get to the point where I don't even notice in a while. during the summer months I do most of my commuting in an older car, so I won't get as many miles to evaluate it again until next winter.

Oh yeah, diesel down to $1.999 within 10 miles of my house. Cumulative economy after 6 tanks: 2860.7 miles at 27.7mpg

Impressive!! Great to see another viable diesel alternative.
Newer diesels have increased efficiency. My ‘20 11,000lb Ram Cummins with a 4.89 rear gets same fuel economy as my 7,500lb 08 F-350 Powerstroke reg cab with 4.10 rear.

 

[Snobdds]

It’s funny how some seemingly unimportant parameter can be exceeded and render lower towing ratings. Wanted to buy a Jeep Gladiator Rubicon Diesel next year and preliminary towing ratings are slightly lower than gas. Now I know few people will tow heavy trailer with a Jeep Gladiator, but it still seemed strange.
I dug a little on the topic and found out the engine compartment couldn’t allow the Diesel engine to cool off enough to take advantage of its superior torque for towing, so they down rated its towing specs.

It is quite revealing to see how a 3L DIESEL has same specs as a gas engine double its displacement.
Diesel engines rock!

Chevy might have to run two radiators like ford did in the 6.7 to get the duty cycle of thermal loads under control. I saw the numbers somewhere that showed two smaller radiators did a better job cooling than one big radiator. The reasoning was most of the heat was removed in the upper half of the radiator which made big radiators have a decreasing return on cooling because there was not enough surface area on the top half to carry the heat away. Another simple fix was to slow the flow through the radiator to maximize the heat transfer through the radiator. The problem was the high flow was needed in the engine block, but low flow in the radiator. They could not differentiate the two different flow rates with one water pump.

It always amazes me that diesels make no heat idling, but put a load on them and the heat gets hot quick. I think it must be due to the higher BTU content in diesel...