Another "What Oil Thread"
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More Turbo
Joined: Jun 2023
Posts: 623
Likes: 264
Another "What Oil Thread"
Anyone using Rotella T6 5W-40? Truck is not a daily driver and has a TC in the bed 99% of the time in addition to towing a 6500lb boat and is used for longer trips. Summer temps would ~80 degrees when towing and in winter I stay in 25th parallel so it averages mid 70's.
Lead Driver
Joined: Feb 2005
Posts: 7,975
Likes: 2,670
From: The Great State of Texas
Also your prioritizing fuel diluted oil cold viscosity over operational temperature oil viscosity. Why?
Did you know that the ambient viscosity of a 10W30 and a 5W40 are very similar.
Ford recommends a 5W40 or 15W40 when running B6-B20 which Bio is known to dilute the oil more.
Can't imagine how much diesel in the crankcase it would take to dilute the oil but a 40wt is going to allow more fuel and still provide the necessary protection. If you check your oil, once in a while, you should see a rise on the dipstick and know something is wrong. Your concern is more towards the 6.4PSD. I've never seen my 6.7PSD make oil.
Lead Driver
Joined: Feb 2005
Posts: 7,975
Likes: 2,670
From: The Great State of Texas
I use Rotella T6 since it's listed on Fords approved oil list. Also Valvoline 5W40 is used by some members here as well and it's on Fords list as well.
Tuned
Joined: Jan 2002
Posts: 409
Likes: 106
From: Wasilla
+1 for Valvoline 5W40 Premium Blue Extreme... unless it gets really cold then Mobil Delvac 0W-40. Russ
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Cargo Master
Joined: Oct 2011
Posts: 2,888
Likes: 779
From: SoCal/Wyoming
In those temps, I would run T6 15W-40. That’s what I run in mine as we see very high summer temps and the winter temps around here are not bad. Daily high temps in the winter usually run in the mid 60s. If I had to make a drive to Wyoming in the winter, I would change it out for a lower weight oil. If T6 came in a 50 weight, I would probably run that as summer temps can hit 115 here.
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Senior User
Joined: Nov 2014
Posts: 1,777
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From: France
the 5 weight is cold and is thicker than the 40 weight (when hot), so 5w40 in your case is better than 10w30
FTE Legend
Joined: Mar 2017
Posts: 31,967
Likes: 9,197
From: Western NY
I'm batting around going to a 5w40 after my stash of 10w30 is used up due to the engine getting up in mileage and for more protection of a 40 weight oil...
If I was concerned about fuel dilution, i would use 5w40 instead of the 10w30 I'm using... I've had slight fuel dilution before but nothing crazy. My truck doesnt idle much and is usually moving...
If I was concerned about fuel dilution, i would use 5w40 instead of the 10w30 I'm using... I've had slight fuel dilution before but nothing crazy. My truck doesnt idle much and is usually moving...
Last edited by Overkill2; Nov 11, 2024 at 10:09 AM. Reason: Correct post
Fleet Mechanic
Joined: Oct 2022
Posts: 1,823
Likes: 898
From: Dallas Metroplex
I was thinking something similar, for the hot temps in summer here in Texas. But, discovered that T6 doesn't come in 50W, unfortunately (not that I've found). I plan to continue to research other manufacturers that provide such in a quality synthetic (Valvoline, Mobil, etc).
Cargo Master
Joined: Jan 2006
Posts: 3,012
Likes: 90
From: SE. MA
It doesnt take much to fall in the category of severe duty requirements, I say just run the 5-40 synthetic and be done with it. Its not much more expensive, its better protection IMO and you cover most of the basses. I have run T-6 5w-40 and VPB 5w-40, I like the VPB better and the truck seems to run a bit smoother and quiter....could be subjective.
Cargo Master
Joined: Oct 2011
Posts: 2,888
Likes: 779
From: SoCal/Wyoming
I was thinking something similar, for the hot temps in summer here in Texas. But, discovered that T6 doesn't come in 50W, unfortunately (not that I've found). I plan to continue to research other manufacturers that provide such in a quality synthetic (Valvoline, Mobil, etc).
Fleet Mechanic
Joined: Oct 2022
Posts: 1,823
Likes: 898
From: Dallas Metroplex
Good idea, thanks. I run M1 in my old Vette, as it naturally runs hot. Great oil for high temp engines, for sure. I'll add M1 15W-50 to my summertime list.
Cargo Master
Joined: Jul 2011
Posts: 2,677
Likes: 979
From: Walpole, MA
https://www.mobil.com/en/lubricants/...mobil-1-15w-50
https://www.mystiklubes.com/do/product/663004002