Ive been running 10w 40 castrol gtx since i got my motor rebuilt. it has about 2000 miles. Been hearing that it would be better to run shell rotella 15w 40 diesal oil. Is there any reason to not do this? Is it okay for cold start ups winter, i live in new jersey . Is this oil a snythetic oil? What is actualy better about this oil?

 

I'd stick with the 10-40. The 15-40 would be a little heavy for cold starts, in my opinion. Shell does make a synthetic, it comes in a blue jug, it's a 5-40 I believe. Good luck.

 

The Rotella 5W-40 is a semi-synthetic
and does a great job in my 7.3L PSD,year round.
Nut

 

probly should have said i have a 351 windsor

 

Diesel oil is actually better for gassers in some situations because of the special
additives,from what i hear. Correct me u oil guru's if i'm wrong.
Nut

 

It depends on which diesel oil you use.

Older CH-4 oils had a lot of ZDDP antiwear additive. Newer CI-4+, not so much because of newer diesels having cats.

Both still have lots of detergent.

Modern API SM gasser oils are extremely good,and I doubt that there is much benefit to running a diesel oil over an API SM gasser oil.

I would not run 10w-40. Substitute a 10w-30. Better yet, a straight 30w.

 

any other thoughts ?

 

I would stay away from the diesel rated oils for your engine. First, I would not suggest an oil that heavy. You really need to be using a 5w-30. The Pennzoil and Havoline oils are turning in the lowest wear metals. As far as a diesel rated oil, you MAY end up glazing the cylinder walls with the calcium used to neutralize the acids formed mostly in a diesel environment. It would be an extreme of overbasing. I have used it in all of my FEs but they are a little different breed of engine. If your engine starts using oil, it will most likely be due to the use of a diesel rated oil. As far as I am aware, the only fix is to hone the cylinders. Chose wisely, grasshopper.

 

That might depend on how the engine was rebuild. If newer alloy metal rings were used, oil usage might be OK with a multi-vis. If cast iron rings were used, a multi-vis might increase oil usage.

And yes, some engine rebuilders still use cast iron rings.

But you are correct, despite the concern over using a "thin" 5w oil, the viscosity at temp in a 5w-30 oil is just as good as a 10w-30. Plus 5w-30's flow a little better when cold.

 

has plasma pro moly rings, and dont rember all the exact names for the bearings but they where performance ones off summit racincs site.

 

You didn't say what type of cam you are using. If you are using a roller cam, then you should be fine with what you are using. If you have a flat tappet cam, then I would switch. Do a search on "flat tappet" or even "rotella" and see what you come up with. I have just gone through all of this myself with my 400 build and the flat tappet cam I'm using. There are numerous threads on this topic, but this thread should answer all your questions:

https://www.ford-trucks.com/forums/s...hlight=rotella

 

okay thank you and sorry i am useing a flat tappet from comp cams

 

After I had my 351 rebuilt, I switched it from 10w40/15w40 to 10w30. That was 3 years ago. Now I use the same weight oil for all my vehicles and equipment. If I lived where you do, I'd probably go for the 5w30.

 

Mine starts & runs just fine with Rotella 15-40 in it to as low as -20 here in Michigan. 7.3L with 369,000 miles so far.
Just about any CLEAN oil will do just fine in your engine. Just change it every 6000 -7500 miles.

 

Keep in mind that diesels require oil of a different viscosity than gas engines, most of the time.

In my '83 F250 with a 460, I now run either Castrol Syntec 0W-30 (aka GC) or Chevron Delo 400 Synthetic 0W-30, and like Horsepuller, I live in SoCal.

It's the "30" part of xW-30 that you need to be concerned about, not the "x", if you catch my drift. In other words, SAE 30, 10W-30, 5W-30 and 0W-30 are all the same viscosity at operating temp; the difference is in the viscosity at start-up temp, where the multi-vis oils will flow better.

The advantage of straight SAE 30 is that it contains no viscosity index improvers, which are long chain molecules that artificially make a lower viscosity oil behave like a higher viscosity oil at high temps. These long chain molecules are subject to mechanical shearing, and thus at some point they cease to perform their function, leaving the oil at the thinner viscosity at all temps.

The 0W-30s listed above also use few viscosity index improvers, due to the naturally high viscosity indices of their basestocks, and because of this they would also work very well in hot climates, particularly the GC, which is a very "thick" 30-weight. The Chevron is somewhat thinner, but has a much higher viscosity index (meaning even though it starts out "thinner," it thins less with heat and remains in viscosity grade) and a significantly better additive package, so it protects quite well in the heat, too.

Oils which use basestocks with naturally high viscosity indices do not require as many viscosity index improvers, and are therefore much less susceptible to "thinning out" due to mechanical shearing. Typically, such basestocks are true synthetics, such as PAOs (Group IV) or polyol esters (Group V), both of which need few (if any) viscosity index improvers to maintain both good flow at low temps and the desired viscosity at high temps. Group II+ and Group III basestocks also require fewer viscosity index improvers than Group I and Group II oils, but more than PAOs and polyol esters. Once broken down, viscosity index improvers can also contribute significantly to the creation of engine deposits.