Diesel questions

[AZCM98]

1. Is it ok to leave the engine running when refueling when towing. Truckers do it.
2. Engine idle time: My truck has run time and idle time, what is too much idle time? Percentage?

Thanks

[Graybuck]

High Idle time may lead to fast plugging of the emission system requiring more DPF cycles, but for short times while fueling it should not be a significant issue. Most auto style fuel stations here in Oregon require you to shut off the vehicle before fueling, but truck pumps may have different rules.

[goducks14]

Why would you want to leave it running?

[TENN22]

Why would you want to leave it running?

From what I have been told, the biggest enemy to a diesel engine is heat build up, since they use the circulating oil to help with cooling, when that oil is not circulating heat is building up extremely quickly, Especially after towing. I was also told to allow my diesel at least a 15 minute "cool down" with engine just idling after a long day of towing. I would think this is even more important with the newer ones that are so restricted with all of the emissions *&!#.

[AZCM98]

With what Tenn22 stated, cool down at the pumps is what I’ve heard also.

[goducks14]

From what I have been told, the biggest enemy to a diesel engine is heat build up, since they use the circulating oil to help with cooling, when that oil is not circulating heat is building up extremely quickly, Especially after towing. I was also told to allow my diesel at least a 15 minute "cool down" with engine just idling after a long day of towing. I would think this is even more important with the newer ones that are so restricted with all of the emissions *&!#.

Agree. OP didn't mention the towing part. When I had my 12 CTD I didn't shut it off if I immediately pulled off the freeway into a rest stop to use the turlet. When pulling in for fuel it usually takes a several mins to actually get in and pull in front of the pump. IIRC Ram required 3-4 mins for cool down after a hard tow. It takes that long to get off the freeway ramp, drive to the fuel station and get next to the pump. Coming off the hwy just cruising at 55-60 I did the same thing.
I see it as if you were towing hard and just shut it down and it stayed shutdown for hours. If you shut it down and restart 5 mins latter then how much did it even cool down in that 5 mins? I never had any issues in 6 years doing what I did.

[JKellerJr]

From what I have been told, the biggest enemy to a diesel engine is heat build up, since they use the circulating oil to help with cooling, when that oil is not circulating heat is building up extremely quickly, Especially after towing. I was also told to allow my diesel at least a 15 minute "cool down" with engine just idling after a long day of towing. I would think this is even more important with the newer ones that are so restricted with all of the emissions *&!#.

Yup, and the new duramax is incorporating a cool down timer for this very reason:

"Sierra Heavy Duty models equipped with the Duramax Diesel also feature an integrated engine after-run cool cooling function, which can continue to idle the engine after extended and exhaustive periods of use, allowing for proper cool-down of vital underhood components."

[goducks14]

All the more reasons I'm glad I went back to a gaser.

[Calnca]

Most auto style fuel stations here in Oregon require you to shut off the vehicle before fueling, but truck pumps may have different rules.

Have the BHLs changed the law so you can pump your own fuel in OR now, or is the full employment law still in effect?

Cal

[Chiefblueman]

Agree. OP didn't mention the towing part. When I had my 12 CTD I didn't shut it off if I immediately pulled off the freeway into a rest stop to use the turlet. When pulling in for fuel it usually takes a several mins to actually get in and pull in front of the pump. IIRC Ram required 3-4 mins for cool down after a hard tow. It takes that long to get off the freeway ramp, drive to the fuel station and get next to the pump. Coming off the hwy just cruising at 55-60 I did the same thing.
I see it as if you were towing hard and just shut it down and it stayed shutdown for hours. If you shut it down and restart 5 mins latter then how much did it even cool down in that 5 mins? I never had any issues in 6 years doing what I did.

The part most vulnerable to heat is the turbocharger. In the days before water cooling the turbo's bearing, they would frequently cook the oil on the bearing if not properly idled down. This would coke the bearing and wear it out sometimes causing the impeller to hit the housing and oiling up the intake tract. I had a little Saab 900 Turbo that did this, so I learned the hard way and replaced a turbo.
The turbo bearings are jacketed and water cooled these days which really helps. In any case, I'd never run hard and immediately kill the engine. Usually when I pull off for fuel there is enough light load and idling that I feel comfortable shutting down to fuel up. Rest stops right off the highway I'll idle for a 2 or 3 minutes. Non towing I don't feel is too critical, unless I've been on boost a lot in the past couple of minutes. Boost = heat.