Anyone here still using 15w40?
- Thread starter 53' Stude
- Start date
Get yourself a 3V Ford with blown tensioner seals (ok, actually, no, don't do that) and you'll appreciate 15W-40 in a small V8 gasser
My father has been a heavy equipment mechanic since the 1970s and still works full time today. He uses 15W40 in EVERY diesel engine including his own personal 2017 L5P Duramax. I don't know that I've ever heard him talk of an engine failure due to maintenance.
Farmer friends 19’ Ram 2500 he bought. 80k
Some ROTELLA T5 synblend and Donaldson dad gave me 14 of. Old filter was Mighty. Chucked right into fire pit. Keeps crackhead neighbors at bay. He called and says running good. I girly 2 dozen fresh eggs to boot.
He asked me bout using 15w40; I said “people I know and talk to would cringe!” He said ok, we will do 10w30.
Some ROTELLA T5 synblend and Donaldson dad gave me 14 of. Old filter was Mighty. Chucked right into fire pit. Keeps crackhead neighbors at bay. He called and says running good. I girly 2 dozen fresh eggs to boot.
He asked me bout using 15w40; I said “people I know and talk to would cringe!” He said ok, we will do 10w30.
Kind of on the fence about 15w40 lately with temps in Michigan that can range from -19F to 100+ I’ve been using a lot more 5w40 the last few years. Starts are easier no matter what season. Last 15w40 I used was probably in August in the portable generator because it was hot and we went without power for three days. Rural King 10w30 HDEO in some of my other small engines because it’s cheap and gets changed every other year.
Still using 15w40 on pre updated 6.7 cummins trucks like 18 and older. No issues here. Any issues on those typically stemmed from lack of owner maintenance not the actual oil itself
On the 19 and up i use 5w40.
I think the main reason they were so adamant about the no 15w40 was the conventional vs syn/syn blend factor. They could have just said they want and require synthetic oil. There are 15w40 synthetic but just not as commonly found.
I do know there are plenty of small and or large aftermarket shops that still just pour bulk 15w40 in those 6.7s 19+
My shop I don’t see many hard part engine failures on diesels at all. Would say if I do it’s a poorly maintained truck with quite a few miles and the owner always acts surprised
Yet never seen an engine issue on one I have maintained from new
On the 19 and up i use 5w40.
I think the main reason they were so adamant about the no 15w40 was the conventional vs syn/syn blend factor. They could have just said they want and require synthetic oil. There are 15w40 synthetic but just not as commonly found.
I do know there are plenty of small and or large aftermarket shops that still just pour bulk 15w40 in those 6.7s 19+
My shop I don’t see many hard part engine failures on diesels at all. Would say if I do it’s a poorly maintained truck with quite a few miles and the owner always acts surprised
Yet never seen an engine issue on one I have maintained from new
Used Delvac 1300 Super 15-40 until about 180k in our Ford 6.0 diesel, then switched to Delvac Extreme synthetic 15-40 and it's at 255k miles and going strong. UOA consistently shows only 6ppm of iron. Very reliable truck...stock heads have never been off the truck.
I use 15w-40 T5 in my 2006 Duramax. We don't see weather outside of 0-100, so by the manual I could have my choice of grade, but they specify 15w-40 is preferred. I see little benefit to the experiment for a truck that gets very little drive time during the colder months. Even in the summer, cold starts are 80 psi at idle. Probably excessive but I don't see the problem in it.
I want the 40 weight hot. When we tow our camper in the big hills, oil pressure will drop as oil temp increases on sustained grade pulls. Below a certain point the piston cooling jets cut off and that's a situation that would pretty quickly lead to ventilated pistons while under load.
Someday I'll put a late model (2020+ L5P) oil cooler on the truck (twice the heat exchanger surface area) to remedy the issue, but I don't see a reason to go away from 15w-40.
There are lots of these older trucks on the road and the diesel truck community is especially resistant to change. I hope to see 15w-40 HDEO without the SN rating at Wal-Mart for a very long time.
I want the 40 weight hot. When we tow our camper in the big hills, oil pressure will drop as oil temp increases on sustained grade pulls. Below a certain point the piston cooling jets cut off and that's a situation that would pretty quickly lead to ventilated pistons while under load.
Someday I'll put a late model (2020+ L5P) oil cooler on the truck (twice the heat exchanger surface area) to remedy the issue, but I don't see a reason to go away from 15w-40.
There are lots of these older trucks on the road and the diesel truck community is especially resistant to change. I hope to see 15w-40 HDEO without the SN rating at Wal-Mart for a very long time.
Last edited:
There are also quite a few older diesels out there that spec 15w40 compared to the newer ones recommending 10w30. So probably why 15w40 is more popular.
I don't doubt the 10w30 is perfectly capable, my issue is availability. Not many 5 gallon or 2.5 gallon containers of 10w30 HDEO available, same with the gallon jugs. The 10w30 HDEO that is available is usually more expensive than comparable 15w40. My local TSC and WalMart are good examples. They have maybe 5 or 6 options for 15w40, but 1 of 10w30 HDEO and the 10w30 is significantly more expensive per quart.
My Harbor Freight 3500 generator manual says to use 15-40.
I use it my antiques (Willys jeeps mostly) instead of the various additives (zinc, lead substitute, etc.) and haven't had any issues. I originally found it with the "S" (spark ignition, it stands for, I think) in the rating but the last pail only had the "C" designation (Combustion ignition, ie diesel, I've been told). My '55 Willys plow truck parks in my shop, which is heated when I'm working in it, so it rarely gets below freezing in there for very long, as far as starting it, but since the thermostat keeps the operating temp at 180, I'm not concerned with the "too thick for cold weather" thing, and that's with a 6 volt system.
16+ year old equipment is not the majority of the HDEO market.
Average fleet age is somewhere around 11.5 last I checked. It went out a bit because of Covid. However, the majority of daily use (and thus oil volume) is newer equipment.
For over the road trucks likely yes, farm equipment definitely not.
Majority of HDEO volume is in operations that run “24/7” - HDEO, Mining, construction/yellow iron, power generation and large agricultural.
Sure, I myself have a 350 acre farm and a great 1964 IH 806 with a 1206 turbo. But my once a year oil change in it doesn’t mean much in the scheme of HDEO fleet usage. Let alone my CaseIH Maxxum 140 Pro can take 10w30.
The point is, 10w30 HDEO “should” be around 60% of the volume of HDEO out there right now. It’s simply the fact the consumers don’t want to switch, for whatever reason. Education, good enough, price, etc. as I mentioned earlier in this thread. By 2027 10w30 “should” be in excess of 75% of the HDEO volume, with other low viscosity oils such as 5w30 But; with current trends it’s going to be lucky to break 40%.
Easy as that. The antidotes of “well my old tractor..” are nice, yes. But not the primary consumer of HDEO products. On road > Construction > Ag > Power Generation > Mining - in about that order. Most large farms use new tractors. Heck even my 2008 Deere 2305 calls for 10w30. “Every day” hard use stuff - it’s getting harder and harder to maintain more Classic equipment.
I haven't used it in many years. Not even in my 1984 Oldsmobile with a 76 350 Olds or any of my OPE. We get cold weather here in Canada and I don't see a reason to use anything other than m1 0w40 that I buy on sale for $34 Canadian for 5 qts.
I run 15w50 in this beast!
4WD
$50 site donor 2024
Sharp !
Only due to Gov regs. Oil consumption has become alot more common in engines used under heavy loads since manufacturers have switched to lighter oils.
Similar threads
- Sticky