Oil viscosity questions
Thread Starter
|
Mountain Pass
Joined: Apr 2017
Posts: 185
Likes: 47
From: fulltime rvers
Oil viscosity questions
2015 6.7 towing a 5th wheel camper. We tow about 6k miles a year and then 5k without the trailer.
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
Logistics Pro
Joined: Aug 2006
Posts: 4,477
Likes: 4,069
From: Raceland, La.
2015 6.7 towing a 5th wheel camper. We tow about 6k miles a year and then 5k without the trailer.
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
Lead Driver
Joined: Dec 2020
Posts: 8,641
Likes: 2,435
Depending on the time of year you travel, any of the viscosities above would work, but as you said, your use is defined as severe duty or special operating conditions. 5w40 would be Fords suggestion. It also happens to be the only one that is a full synthetic, at least from Motorcraft. Both the 10w30 and 15w40 are conventional oil. I wonder if 5w40 is called out for severe duty because of the viscosity, or because it's a full synthetic.
Logistics Pro
Joined: Sep 2002
Posts: 4,414
Likes: 1,018
From: Central KY
For what it's worth, my truck had nothing but Motorcraft 10W30 as far as I can tell for the first 81,000 miles because the Carfax showed that the dealers had done the oil changes, and the truck had obviously been used for work and towing. When I pulled my CAC hose to look inside the lower intake, the soot accumulation was much less than what I see on other people's trucks when they post pics on social media and on this forum. Some guys even commented on mine saying "that doesn't look bad for the mileage!". So I'm a believer in the Motorcraft oil.
I did just a couple of weeks ago use Rotella T6 because I wanted to see if it would eliminate the "marbles in a can" noise that happens on startup sometimes (there's a TSB for this, it's common). It did not. So I may go back to the Motorcraft next time. We'll see.
I did just a couple of weeks ago use Rotella T6 because I wanted to see if it would eliminate the "marbles in a can" noise that happens on startup sometimes (there's a TSB for this, it's common). It did not. So I may go back to the Motorcraft next time. We'll see.
Cargo Master
Joined: Jul 2011
Posts: 2,679
Likes: 983
From: Walpole, MA
MC oil, especially the 10w30 ck4, is a very good option. Ford is a little proud of it but it is solid option.
Honestly, most UOAs I have seen that even under load a good CK-4 10w30 really shouldn't have any issue. A lot of folks go the 5w40 route cause it covers pretty much everything so it one less thing to worry about, Rotella T6 is usually one of the more cost effective options. If your REALLY curious about how the oil is doing, pull a UOA when you change your oil.
Personally, I am running travellers 15w40 in mine cause based on use I will need to change the oil before it gets cold again and I wanted to see how the truck would respond to a conventional 15w40. I am a fan of the big slugs of boron and moly in the tsc house brand but that is a personal preference, not gospel.
Honestly, most UOAs I have seen that even under load a good CK-4 10w30 really shouldn't have any issue. A lot of folks go the 5w40 route cause it covers pretty much everything so it one less thing to worry about, Rotella T6 is usually one of the more cost effective options. If your REALLY curious about how the oil is doing, pull a UOA when you change your oil.
Personally, I am running travellers 15w40 in mine cause based on use I will need to change the oil before it gets cold again and I wanted to see how the truck would respond to a conventional 15w40. I am a fan of the big slugs of boron and moly in the tsc house brand but that is a personal preference, not gospel.
Trending Topics
Hotshot
Joined: Jul 2013
Posts: 14,303
Likes: 2,198
Depending on the time of year you travel, any of the viscosities above would work, but as you said, your use is defined as severe duty or special operating conditions. 5w40 would be Fords suggestion. It also happens to be the only one that is a full synthetic, at least from Motorcraft. Both the 10w30 and 15w40 are conventional oil. I wonder if 5w40 is called out for severe duty because of the viscosity, or because it's a full synthetic.
……………
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Hotshot
Joined: Jul 2013
Posts: 14,303
Likes: 2,198
For what it's worth, my truck had nothing but Motorcraft 10W30 as far as I can tell for the first 81,000 miles because the Carfax showed that the dealers had done the oil changes, and the truck had obviously been used for work and towing. When I pulled my CAC hose to look inside the lower intake, the soot accumulation was much less than what I see on other people's trucks when they post pics on social media and on this forum. Some guys even commented on mine saying "that doesn't look bad for the mileage!". So I'm a believer in the Motorcraft oil.
I did just a couple of weeks ago use Rotella T6 because I wanted to see if it would eliminate the "marbles in a can" noise that happens on startup sometimes (there's a TSB for this, it's common). It did not. So I may go back to the Motorcraft next time. We'll see.
I did just a couple of weeks ago use Rotella T6 because I wanted to see if it would eliminate the "marbles in a can" noise that happens on startup sometimes (there's a TSB for this, it's common). It did not. So I may go back to the Motorcraft next time. We'll see.
I get less marbles in a can with 15w40
i just have to watch my cold weather temps and is a block heater below 20 degrees which is rare
Lead Driver
Joined: Dec 2020
Posts: 8,641
Likes: 2,435
So Fritz is thinking because of the 40w, and you are thinking maybe because of the 5w......5w40 does covers all possible severe duty temperature scenarios. I think they say if you operate in -10f or over 100f then that is severe duty. But why call for 5w40 for low speed operation, towing, idling, dusty conditions, if the vehicle is not operated in an area that sees those kind of cold or hot temperatures.
Laughing Gas
Joined: Oct 2014
Posts: 962
Likes: 114
From: Middle TN
2015 6.7 towing a 5th wheel camper. We tow about 6k miles a year and then 5k without the trailer.
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
I did my first oil change at a dealer and they recommended 10w 30 which is what I have been using all along. Talking with a friend and he uses 5w 40. I do see in the manual that it is recommended for severe duty, towing a trailer.
should I switch to 5w 40 or stay with 10w 30.
Thoughts
Thanks
Run the 5W-40 and reasonable OCI's, and forget about it.
Laughing Gas
Joined: Oct 2014
Posts: 962
Likes: 114
From: Middle TN
Because 5W-40 and 15W-40 are the same viscosity at operating temp. The 5W-40 will flow better in cold weather and cold starts.