SAE 40

[Matt97]

Very interesting, blows the theory of thinner oils being the ultimate out of the water.

 

[userfriendly]

Oil Fairy tales 101;
Back in the day, 15W40 was a wildcat grade. Likely achieved by mixing SAE 50 and 10W30 together. As time progressed, 15W40 became thicker almost to the point of being 20W50. About the time this board was started, one of the majors flunked the 15W specification which was not as stringent as it is now.

 

[jeff78]

Surprised you can still get SG oil.

I run VR1 SAE 40 in a (modern) liquid cooled shared sump motorcycle. It's not recommended for wet clutches, but I haven't had any issues in 2 years. The VR1 data sheet says this is an SN oil, but the bottle only says 'Exceeds API SL'.

Monogrades don't (can't) shear, which is a major plus on shared sump engines or any engine that is known to shear oil heavily. If freezing starts aren't a concern, I don't see anything wrong with running a monograde.

VR1 has a big fat slug of ZDDP in it as well.

VR1 SAE 40 UOA

 

[Matt97]

SG grade popular over here on monogrades. Later specs on monogrades are rare, almost as if being reserved for other grades

 

[jeff78]

Originally Posted by Matt97
SG grade popular over here on monogrades. Later specs on monogrades are rare, almost as if being reserved for other grades


Ah, did not see your location.

Have you done any used oil analyses on these oils? I'm curious to see what their additive packs look like.

 

[Matt97]

They work well on older Diesels, SA has 50ppm diesel with 500ppm still availible. I wouldnt use in modern engines, there i stick to the manufacturers grades, my main usage of SAE 40 is clients older vehicles which have older design engines that are now burning or leaking oil to an extent. The 40 helps alot in this regard while decreasing valve train noise.

 

[caprice_2nv]

I'd like to try a good straight 30 weight in my 76 350 Oldsmobile in my summer daily driver. I always assumed they were old school, out of date nothing special oils. I've used everything from 0w30 to 15w50 in it and discovered while oil pressure is higher with thicker oils anything with a 30 weight (5w30 or 10w30 synthetic or conventional any brand at all) the valvetrain is silent while I hear some very minor tapping with thicker oils.

I can buy a 5 gallon barrel of 30 weight delo or other equivalent for $3 a QT. I'm looking for the lowest wear but if straight 30 conventional cost less and gives the same wear I'll switch from synthetic.

 

[Matt97]

Try it. The Api grading will be more than sufficient, plus the cost will work out more favorable. I've never understood the mantra of using a higher spec than what the manufacturer calls for , nor the obsession with miniscule differences in analysis results.

 

[caprice_2nv]

So far my experience has been the cold number had no effect on the noise in my car, just the second number. I haven't done any uoa and have no other metric to go by other than sound and oil pressure. Oil pressure is slightly low with 30weight oils but the engine is silent.

I need to get a good place for a used oil analysis kit that also tests for fuel dilution (since both my cars are carbureted). The winter car I'm going to keep running a 5w30 synthetic or 0w30 synthetic but I can run a straight 30 weight in it for summer time also. The 305 doesn't need to last forever because I'm swapping a 5.3 in the next couple of years.

The Oldsmobile I'm going to run the 350 as long as I can before it needs work.