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If you are using DINO oil then, cool down is probably a good thing. Dino oil burns if it gets too hot and leaves a residue that will attach itself to the turbo bearings and bearing failure will probably follow.
If you use SYNTHETIC oil then, turbo cool down is irrelevant. Synthetic oil will not burn and leave a residue to attach to the turbo bearings.
DSMMH
synthetic will build up coke on the bearings, just not as bad as it can handle higher tenps than dino juice.
What I don't understand is why the temperture in the EXHAUST manifold has ANYTHING to do with oil temperture... For instance, I drove back home yesterday from upstate NY to Baltimore area. Before stopping for fuel - food, etc. My EGT gage would be down to 400 (from upwards to 1000-1200 F) by the time I got off the exit ramp and idled to the parking lot. I went more by my oil temp age. It stayed pretty close to 180-185 ALL the time. As I don't have a pre-turbo EGT gage, it's always a guess to know when it's okay to shut off engine. Same as a previous person said, if it was THAT big a thing, Ford would have installed a turbo bearing temp gage. I did same thing with my previous F250 (92) with a Banks turbo in it. Drove it forever, never had a problem.
i'am going to take a stab at this if im incorrect some please set me straight but as i understand it. i would assume that the oil temp is relatively always going to be withing your stated ranges.when they design an engine it is designed with a min and max operating temp. and clearances are made with this temp in mind so the oil should be within those ranges for the engine to be operating efficiently. while the exhaust temp will vary depending on load. your oil is not being cooled to much extent by idlling. but the exhaust gases have to pass through the turbo. and 1300 degress is going to make the turbines red hot and possibly boil the oil if shut off instantly while 400 degree air will not boil the oil. does that make any sense, i confused myself. lol
This is a interesting read, this is one of my concerns when I was looking at a diesel. Ive never owned a diesel, however i would like to.
Everybody kept saying you gotta let it run and cool down before you shut it off.
Since some days I make several small trips to town to get parts or run erands, I cant for the life of me see me sitting in the truck for 3 to 5 minutes waiting for it to cool down before a quick trips inside to pick up what i need then leave. The cool down would most times last longer then the trip inside?
I sure cant see letting it run for 10 minutes, what a waste of fuel!
I agree with the poster above that if its such a big issue shouldnt ford have put the turbo saver or the gauges in the truck to begin with.
So my question still remains at what point can you be safe and just shut it off. and at what point dont you?
Diesel uses next to nothing for fuel to idle. I've left mine idiling in a parking lot for 45 mins and it only dropped .2mpg. Most of my trips are short and a lot of just coasting along so it doesn't get too hot. They actually also say that if you let it idle for 10+ mins you should take it for short spin to clear out the carbon buildup from unburnt fuel. I generally let mine cool for as long as it takes the windows to roll up. If I travel about 12 miles city I give it a min to two. 20+ miles up to 5 mins. Turbo is covered under 5-year/100k warranty with $100 deductible so if the bearings cook and quit spinning all you got to say is I let the damn thing cool for 10 mins everytime like the manual said to.
My trips to town from work or home would be like 4 to 5 miles one way. So basically 5 minutes to town to go pick something up for work. Then your saying let it cool for 2 minutes before shutting it down?
Im having a hard time grasping the idea as my routine is pretty close to...Pull in to parking spot...as your Grabing wallet...as you Throw it into park as my other hand is opening the door.....
Maybe I just need to slow down a bit...
well, my trip to work is like a quarter mile and takes about a minute and a half so I'm opening the door before it's in park and already starting to turn the key to off. It really doesn't get hot coasting down a hill. If you're going 5 miles up a hill with a headwind you may want to give it a minute to cool, otherwise it's not a huge deal. There's 15 quarts of oil that needs to reach the max operating temp, and then the bearings have to be hot enough to cook the hot oil that's sitting on them. I don't think in 5 miles it'll really get 15 quarts of oil up to max operating temp and the turbo bearings red hot. So maybe 10 seconds to get some oil flowing over the bearings and carry what little heat there is off them.
My overall average is 12.2 mpg. That's about where it sits for me as I live in an area with a lot of long steep hills. If I get in with traffic on a road with more normal grades and move along at around 50 mph I see about 15 mpg. On an open flat stretch of deserted road where I can granny the pedal I see it climb to 20+ mpg but as soon as I turn onto a hill it's down to 13 mpg by the time I'm at the top, lol. But looking at the mileage records for my 98 f-150 with 4.6 I was averaging 11.9 mpg.