Detergent or Non-detergent

[Ts & As]

That is the question.

What is your opinion on using detergent vs. non-detergent oil? The original 312 engine has NOT been completely rebuilt since it ran fine when I took it off the road and it has 79,000 on it. (Somebody before me was into the heads). Good compression and did not smoke. Did have significant sludge in the pan which I cleaned out and poured gallons of Kero through the heads to loosen up anything that may be caught up in the ports. The car did have an auxiliary oiler from the oil sender up into the valve covers since the oil pump screen was buried in the pan sludge (which I have removed). Argument that I have heard is that detergent oil will attack sludge and clog up ports. I think if that was going to happen - I accomplished it already with the kero flush. Also with the PER 1 Filter - seems that detergent makes sense.

Now have 300 more miles on it (all non-detergent so far) I was thinking to change over.

Would like to hear what others have done? Also what SAE would you recommend?

 

[Winston]

You shouldn't really say detergent. It's the detergent/dispersant package. They get talked about together. The detergent cleans and keeps it clean. While the dispersant captures the dirt, suspends it and allows the filter to do it's job. You can use an engine flush, which there are a couple good ones on the market. Keep in mind, if you end up with some drips after that (even with the kero), it's because the sludge from the petroleum oil has coated the seals and hasn't been allowing the seal swell additive in the oil to get to the seal. Once you wash that off with the flush it takes awhile before the swell additives can work on the seal(if at all).Don't know how that theory works on rope seals though. Viscosity of oil should be chosen based on clearances. Fresh tight engines don't like heavier oils. SAE 30 or single grade oils are a thing of the past as far as i'm concerned. Generally, industry uses them in equipment that sits in a plant all day. Doesn't see cold temperatures. Multi grade is the way to go and it's especially helpful during start ups.

 

[Ts & As]

Winston - sounds lik eyou are in the business. So if I understand correctly - after a good flush - Modern SAE 5W30 multiviscosity oil should be good to run in the old 312. For now I am weening my way in with 50% non-detergent and 50% 5W30 and a brand new filter. Engine seems tight except for a slight drip from the access cover on the oil pump. Is that OK for the next 500 miles until I change to all modern oil?

Thanx
Tom R.

 

[Winston]

I like to read a lot (not an expert). . I would maybe use 10w or 15w40. And it would be a diesel oil. They have a more robust additive package to more better handle sludge,blow-by, heat, etc.. Synthetic would be better yet.

 

[sc1956]

Rotella 15-40 is a good choice.

 

[Ts & As]

Winston & Stephen Thanx

Is the Rotella you mention the same as described in the following article. It appears to by synthetic and designed for diesel engines.
http://www.thedieselstop.com/contents/getitems.php3?Shell%20Rotella%20Oil

I do have a small amount of blow by -maybe that will tighten things up a bit?

Tom R.

 

[sc1956]

Yes, I've always used the Rotella T. A good friend in Houston was an engineer with both Shell and Texaco, specifically in lubricants for 25 years. He now can't stand Shell as a company, but swears it's the only thing to use.