What is a Good Synthetic Oil to Use?

I'm using Royal Purple 5-30 for summer. It has the older SL rating which means more zinc than the newer SM rating. The thinner oil allows your oil cooler to be more efficient.

If it leaks, does Royal Purple show up better?

Was just wondering about the "5" end of the scale. Not to thin?. I put that into my wifes Sonata and its like water! John

personally, I still stick with mineral oil. At our shop, we use Kendall GT1 20W50 mineral or Mobil 1 15W50 for all aircooled Porsches. Mobil 1 always for race engines. I was never a Mobil fan but I suppose it works.

I think I will use 20 W50 dino oil instead of the usual 30HD this Summer.

I don't know if that really helps or not. The dual-relief system, if I understand it correctly, has two plungers that regulate the oil pressure. The relief one, which I think is in the front of the case(front being front of car) bleeds excessive oil pressure directly back into the sump. The bypass valve OTOH is designed to divert oil away from the oil cooler when the oil is cold, thus helping warm-up faster.

But that system was built on the idea that oils were not multi-grade at that time. So if you put straight 30 in there, as it warms up and thins out, two things happen. The relief valve closes more to keep the oil pressure up. AND the bypass valve closes, sending oil through the cooler.

If your 20w-50 oil thickens up to approximately 50 weight as it gets hot, which I think is what it is supposed to do, then two things happens. The oil pressure remains relatively high, potentially keeping the relief valve open. But that also causes the bypass valve to stay open, preventing the oil from going to the cooler because based on the thickness of the oil.

I could be completely wrong, and Bob Hoover would probably be a much more authoritative source on this. But this is how I have come to comprehend what happens as the engine warms up with straight-weight versus multi-weight oils. As a further point of interest, the original owners manual I have for my 74 super does not mention multi-grade oils at all with the exception of SAW 20W-20. I have no idea what that was. Other than 20W-20, which may have been a typo, it just lists different temperature ranges, and the proper straight-weight oil to use from 5w up to 40w. It also mentions service grade SD or SE as being required for a VW engine.

Hope that helps.

Chris

The "5W" means that it flows like 5 weight oil when it is cold and I believe that cold is defined as 0 degrees centigrade. So if it is 70 degrees F (21C) then the oil would flow like 10 weight.

The "30" means if flows like 30 weight when it is hot (I believe 100C)

Unless it is cold outside and the oil is very thick from being cold, I do not see any problems with 20 W 50 affecting the oil pressure relief and control valves or bursting the oil cooler from too much pressure.

The following is from =91More Than You Ever Wanted to Know About Motor Oil=92 By Ed Hackett edh_at_maxey.unr.edu

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates.

Another way of looking at multi-vis oils is to think of a 20W-50 as a

20 weight oil that will not thin more than a 50 weight would when hot.

bursting the cooler is less of an issue than having a 50 weight rated oil... At operating temperature it can, and will in a healthy engine, cause the bypass valve to remain open, or partially open, and oil will bypass the cooler.. I used to run the 20-50 weight because everyone said it was what vw's "needed"... they also said it didn't need the thermostat, all vw's have shitty heat, and that it needed a relay or the starter wouldn't work... all those things have proven to be horseshit over the years...

I think I will stick with conventional non synthetic 10 W30 in all but hot weather and in hot weather I will use 30HD.

I don't understand that line of thought.... 10w30 is the same viscosity at operating temperatures as straight 30 weight oil... where the 30 weight is bettered by the multi-viscosity oil is at startup... at startup straight

30 weight oil is very thick...

You forgot the -009. Gotta have one of those if you want your ride to run correctly. Oh..and cut those pre-heat tubes off already...jeez.

:-)

Chris

Dont forget backing off the chokes!. Dont need them in Aust. After fiddling around with them for 40 years on and off I,ve found that the best setting is where the service manual says!. Know it all b..........s. John

You forgot the -009. Gotta have one of those if you want your ride to run correctly. Oh..and cut those pre-heat tubes off already...jeez.

:-)

Chris

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isn't that the truth....

Just go to Walmart and grab a jug of Rotella straight 30wt HDEO. It still has lots of the "old" additives that the big-rig trucks still use and it's cheap. IMO, the problems with synthetics in an ACVW are that 1. it's expensive and 2. chances are it's real benefit of extended oil drain intervals won't be realized in these motors since the oil will become fuel-contaminated in a short period of time. Get a jug of Rotella or Delo and you can change the oil twice as often which is really the best thing you can do for your motor. These oils also come in a 15-40, but 30 seems the way to go. Bill.

The Rotella T is also available in 10w30 which I've been using for years.

And I wish I could say that I've never had a problem with it. But I am now redoing my 1776 at ~25k miles because of pitted lifters, scuffed up cam lobes and loose lifter bores. :-\

Anyway, I've located a local speed shop that carries Brad Penn and that's all I'll be using from now on. I bought a case of their Penn Grade 1

10w30 on the way home today.

Max

That ounds good but, I like to buy my oil at the locals F.L.A.P.S./ Auto Zone.

Even there Rotella is only a couples of dollars more than Wallyworld.

I think I am going to stick with Castrol 10 W30 in all but hot weather and in hot weather use Castrol 30HD. How ever I might start using a synthetic-conventional oil blend. Does Castrol make a synthetic blend 20 W50?

I change it at least every 1000 miles and I do not mind paying more for the synthetic.

I was getting the 10w30 Rotella at Napa. They're pretty friendly. :)

Max

fuel dilution isn't what gets the oil the fastest, it's the engine case ventilation system that does... using outside, and unfiltered, air to ventilate the case puts contaminates(think moisture and dust) in the oil...