PCA0891

I would like a recommendation on the best possible engine oil for what is now a Boosted Engine and living in Hot Nashville Tn. I currently have Castrol GTX SEA 20W-50 running in the car. This oil was added last summer after the purchase during my original tune up and prior to Supercharging so now it's running a bit hotter anyway.

I have just passed the 2000 mile point since then and I would like to change it out prior to heading out to SITM.

Would love a couple of idea's and reason's why.

Thanks in advance

GregBBRD

20/50 Prayer.

These engines have excessive oil pan temperatures, stone stock. Adding all that extra load and heat, from the supercharger, is just going to make this worse. Add in high summer temperatures and you will "see" oil pan temperatures over 280 degrees.

You need another oil cooler.

On top of that, you need an oil that has the proper amount of Zinc and Phosphorus to keep the cams and lifters from "touching each other" and increasing the oil temperature, from friction (not to mention destroying those parts). The "necessary" amount of Zinc and Phosphorus that are need is "assumed" to be 1200ppm. I consider that to be a minimum number, for proper protection. (The 20-50 Castrol that you are using are probably below that 1200ppm.) You can add an additive to bring up the ppm of the Zinc and the Phosphorus (Torco, for one, makes a product called ZEP which is a great additive.....there are others.)

There are oils that can not be found at Walmart, which might be better for the 928 engine. Brad Penn and Torco come to mind, instantly.....there are others. I personally use Torco in all of my 928 engines....from the stock ones to the mega dollar strokers.

The final thing to think about is viscosity and "multi-grade" oils. While the oil manufacturers would lead you to believe that all oils "exchange" or "loose" oil temperatures equally....don't try to tell this to any of the people that really know....like Nascar engine builders. You will never find a multigrade oil in one of these engines....they think (and seem to know) that multi grade oils are much poorer at "letting go" of heat....and use "straight weight" oils, instead.

Which brings up a story.....a few years back, I had the opportunity to go work for a "beginning" Nascar team. Our entire team had the combined knowledge of one of the guys that brings the water to the guys that change tires on one of the bigger teams. We were "fish out of water"....in a huge way.

Anyway, we were "fighting" oil temperature....300 degrees on "short" practice runs. One of the mechanics from one of the "big boy teams" wandered by and looked into our garage. The first thing out of his mouth was "You guys having oil temperature problems?" Of course, this question got our complete attention....and our garage fell silent. Anyway, he pointed at the multi-viscosity oil that we had "stacked up" ready to use and said "Get rid of that **** and go over and get yourself some straight 50 weight....it cools much better."

Needless to say, we did that, instantly....and that single thing cured our oil temperature problems.

Several years have passed since then....but I can tell you this....the last time I did this, on a "high oil temperature race engine"....this was still true and straight weight oil reduced the oil temperature, significantly.

Kiln_Red

Any of Greg's comments sound familiar, Robert?

What is the ZDDP in the oil you are running now? I am not familiar to it.

LexVan

A very good 20W50 weight oil with high zinc (1,700) and phosphorus (1,600) is Mobil V-Twin. Many of us on the 993 and 993 Turbo Forum run this oil. Easy to find. About $11/quart.

Kiln_Red

I wouldn't have any issue with that recommendation if it weren't for the fact that Robert is running high flow cats.

BC

Can a 50 weight oil be used when the temps are between 60 and 100?

Seems feasible.

LexVan

Then look into Joe Gibbs DT50 15W50.

Speedtoys

So he'll only gt 80k out of them, not 100k.


That's what bothered the OEMs..slightly less use.


And..depending what his cats are, they may only work for a few years at all..most of the low cost ones are not very long life.

redpathtribe

Using Mobil 1 15-50 here in Phoenix, where it doesn't get much hotter. While you can buy this at Walmart (most of the time anyway), I think it still meets Gregs criteria above.

This leads me to ask Greg a dumb question... Here in Phoenix where during the heat of the summer it doesn't get below 90 deg. F even over night, would it ever make sense in a street car to run straight 50W to improve engine cooling and reduce heat (and wear?)?

PCA0891

I have 150 CPI cats from Roger I would think they are of a good or bst quality I can't remember the manufacturer.

However now that I have gone to a Historic Tag I no longer need to deal with emissions. Depending on the Cat or No Cat thinking it may change soon anyway.

I need to buy the best available oil for the conditions at which it will be driven. Who cares about the cost of 9 Quarts of oil when it comes to the life of my motor.



I like Greg Browns thinking and have looked for a source for Torco oil.

I have found a local source however now I need to know what weight if there are choices. I will PM Greg.

Austin did everything right when preparing the upper half of my motor now I need to take car of the rest...

bronto

I had low pressure issues during summer trips to Fresno. Switched to Royal Purple and they are gone.

GregBBRD

I personally run 20-50 Torco TR-1R in virtually all of the engines I do. If the customer "has" to have a synthetic, I run Torco SR-1, in those engines.

I still have Mobil One and Castrol 20/50, for the customers that don't want to change.....but I add in the Torco additive....even if they don't want to pay for it.

I have run straight 50 weight in race engines....with great results. Not very often in street cars....but one of these high compression 928 engines with a supercharger added on is under way more stress than most pure race engines. The downside to straight 50 weight is obvious....it's 50 weight when it is cold, too. Warm-up becomes important.

Best thing to do....add an oil pan temperature gauge and monitor. Keep changing things until your oil pan temperatures are under 250 degrees, with a synthetic and under 240 degrees with dyno oil.

ptuomov

Since this is about cooling and lubing a boosted engine and I've been thinking about those recently, let me expose my ignorance and weigh in. Huge caveat lector! I am honestly writing what I think is going on, but that doesn't mean that I am not wrong.

Hotter the oil returning to the sump, more heat it is removing from the engine. Oil returning to the sump being hot is good from the cooling perspective, within reason. Holding the friction constant, that heat is removed from the engine components.

Holding the oil pressure constant, lighter/lower viscosity oil is better from the cooling perspective. That is because less oil gets bypassed by the pressure regulator and more oil flow actually makes it thru the engine. More oil flow thru the engine usually means better cooling, and higher oil temperatures. It also means higher average oil temperature in the oil cooler, and more cooling effect.

I say hotter oil is good within reason because if oil gets too hot it starts to break down. You don't ideally ever want oil to get above that critical temperature. The best place to measure the temperature is in my opinion as close to the entry to the oil galleys, say with a sandwhich plate on the 928. The peak oil temperature is going to take place in the engine bearings, and you can approximate the peak temperature of the oil inside the engine with the oil temperature at the galley entry plus 40 F degrees. That's the number to look at, temp+40F, where the 40F comes from study by Ford Motor Co.

For example, suppose that you run 5W30 Castrol GTX, API SN that some people have measured to start "breaking down" at 280F. If the oil temperature going into the oil galleys is >=240F, then the oil is degrading as the lighter compounds vaporize. I would go and change the oil frequently if going over that sort of temperature readings. New oil still lubricates and protects well even at those temperatures, it just doesn't last very long in that "new" condition. I think the temperatures at which lubrication starts suffering immediately are significantly higher than temperatures at which oil starts ageing faster.

If you have a good oil cooler that both flows a lot of oil and also gets a lot of air flow even in traffic, then I think you should have a good shot at keeping the oil temperature at reasonable levels at the galley entry.

In terms of camshaft and lifter wear, it is my understanding that the whole additive package matters. There's no way to just look at one number and to say that this will protect our valvetrain well. (It may be possible to look at a couple of numbers like Zinc and say that this oil is probably _not_ going to protect... but I can't do it.) The only way to do this is wear test, which of course in this context means observing other people's failures. Therefore, I would stick to oils that both
(1) have given good wear results for others and
(2) the additive package hasn't been dramatically changed since those results were observed.

Finally, I would be very careful with additives that are generic. Different oils have different existing additive packages that react differently to different additives.

Again, a huge caveat lector and think with your own brains warning.

For some interesting reading:
http://www.speedtalk.com/forum/viewtopic.php?t=30483
http://www.speedtalk.com/forum/viewt...hp?f=1&t=31363
http://www.speedtalk.com/forum/viewt...hp?f=1&t=32279

Tony

always wondered what temp to look for. Ive had a pan gauge on for a while here in Vegas.

I would like to add an external cooler as to not have the hot oil temps transfer to the coolant on days like this.

.a hot day in Vegas. as you can see...I dont trust the needle on these cars anymore.

GregBBRD

I'm certainly "estimating" at what I think oil pan temperatures should be. I figure that the oil is going to leave the pan, get pumped through the oil cooler, and then to the bearings. I figure that at 240 or 250 degrees, the oil can still be cooled down by the water in the radiator....perhaps not, by the looks of your two gauges, Tony.

Very interesting.

Makes one wonder if the water temperature is high because of the oil being cooled down by the water. Porsche did "justify" that they removed the oil cooler from the radiators in the later vehicles because the radiator was not able to deal with the thermal load from cooling the oil, as the power output went up.

Do you know if your '87 has the piston sprayers or not? The 968 engines seem to universally have very hot oil/low oil pressure and some people suggest that this is the result of the sprayers.