I've seen many posts on here about people running 15w40 in their 4.0's I was just curious about how this works out .. I own a 2000 with 205000 miles and im wondering if the thicker oil would be good for the old motor or not .. Any advice would be appreciated

 

I've tried lots of different types of oil, and have yet to be convinced that there is any noticeable difference between 10w30, 10w40, or 15wXX in a car or small truck. If it is cold, go for lighter weight. If it is hot, consider heavier.


Just don't use a fram oil filter ><

 

I ran a lot of rotella t through my old 97 4.0.
I also ran it in my CBR and my klr650.
It made things simple. And cheap.

 

15-40 and a tired 4.0 go together like peas and carrots.

 

I run 0w-30. If you don't believe me switch when it's cold out and then you'll believe me.

 

Yeah, if battery has a hard time spinning engine over its time to use a thinner oil. I use 15-40 and do not have that problem at 10 degrees.

 

I had excellent luck using Delo in my 1996 with 200+ on it.

 

I have a 1990 4.0 renix running mobile 1 full synthetic I change often though seems to like it..

 

For 10 deg the factory recommends 5w. Just saying. Not sure why you'd run 15w.

 

10 degrees is a rare occurrence where i live, maybe once or twice a year. My engine is tired with 4 psi oil pressure with 15-40. It has had low pressure since I bought it 4 years and many miles ago. I bought a spare engine and decided "what-the-heck I am going to run 15-40 Walmart oil in it till it blows. Well it still runs like new (except 4 psi) and I am still waiting......

 

Don when I bought mine it had 220,000 on it and sounded a little loose on the top end for sure and made the same decision as you did. Have almost all the new parts and a fresh block in the shop waiting and waiting..............The damn thing just keeps running on now after 3+ yrs and I wondered if it would make it a month till it blew.


I run Rotella in it also a 5w40 and NAPA Gold filters. My DD's the 04 GC with a 4.7HO and the 13 Lincoln Town Car, 09 E-250 High Top Conversion Van all get Castrol 5W40 full Syn and NAPA Gold or Wix filters.


The only high mileage car I have ever ran full syn oil in is my 2004 GC "Overland" with the 4.7HO motor it has 208k and does not use a drop of oil between changes 6mo/6,000mi. It was an one owner car with all service records done on it at a Jeep dealership from day one. It was spotless inside/out.

 

That is why I tell people not to freak out with low oil pressure on a high mileage engine. My motto is "If it ain't knocking,keep rocking".

 

15W-40 is designed for diesel engines. It does not provide good cold start protection in a gasoline engine. So, if you use it, will your engine blow parts through the hood? No. It's just less than optimal.


5W-40 is a no-brainer solution. It will give you excellent cold weather start protection. It will give you excellent operating temperature protection in warm or very hot weather.


Last week, Walmart had Shell Rotella 5W-40 T6 (that's full synthetic) on sale with a $5.00 rebate. You might check to see if that offer is still available. It's outstanding oil with plenty of zinc for the flat tappet cam. Be aware the Rotella T6 comes in 4-quart jugs. I bought two jugs and used most of it with a Motorcraft FL1-A filter which gives an extra 1/2 quart of oil capacity.

 

So what is the difference between a gas and a diesel engine? If anything a diesel with its high compression is even more critical. It is the residual oil film on bearing surfaces that protects an engine on cold start ups. That film is still there with 15-40, probably more so.

 

I always used to catch the rotella t6 rebate offers. They run them quite often, and it's a great way to snag some super cheap, high quality oil. I had like 10 gallons at one point.