rebuild running cooler on 5 30 syn than 20 50 reg oil

p914 · 09-24-2007, 04:13 PM

So my rebuild is done and is finally tuned and dialed in. 2.0 liter to 2.7.
The oil temp averages 240 running on 20 50 regular oil and averages 217 on 5 30 synthetic. Seems like the 20 50 would run cooler as the 5 30 would be to thin.

The rings seated fine so I see no issue there.

Thoughts? Ideas?

I was thinking about a different oil cooler with a fan but if the synth runs cooler, why get one? Would the thinner synth eventually have a problem? I tried with both regular gas and premium.

Funny thing is the engine seems to run smoother with the 20 50.

hardflex · 09-24-2007, 05:35 PM

Synthetic is supposed to less friction, which would explain the lower temps. I noticed the same drop in temps when I switched to synthetic.

Maybe a heavier wt synthetic would be in order?

p914 · 09-24-2007, 06:26 PM

I was thinking 20 50 synthetic as my next step. I saw some Royal Purple on sale for $5 qt

djpateman · 09-26-2007, 08:08 AM

Brad Penn, a successor to Kendall GT, is supposed to have the best performance of the conventional oils. It does have the additives that an air-cooled engine requires, especially our vintage engines.

I guess the oil temperature begs the question: is the engine running hotter with the lower oil temperature, or running cooler? If the oil cannot pick up the heat as efficiently the oil temperature will be lower, but the engine runs hotter. Higher temperature oil should expel more heat from the cooler, all else being equal.

hardflex · 09-26-2007, 08:18 AM

I have heard that argument put forward. All I can say is, I was running conventional oil in my Yamaha xs850 and could feel the heat radiating off the motor as I rode it. Changed to Synthetics and it was noticeably lower.

Tobra · Tobra's Garage

Synthetic oils have a lower specific heat as I understand it, less heat carrying capacity.

Trade off is lower friction

NOTASIX · 09-26-2007, 09:31 AM

Synthetics are not created equally.. Some have bad properties of dissipating heat, but they generally operate better at higher than conventional temps.

I'd say if you are having better results with a 5-30 oil than a 20/50 that your running clearances are tight, maybe a little too tight.

p914 · 09-26-2007, 11:29 AM

Quote:

Originally Posted by NOTASIX

Synthetics are not created equally.. Some have bad properties of dissipating heat, but they generally operate better at higher than conventional temps.

I'd say if you are having better results with a 5-30 oil than a 20/50 that your running clearances are tight, maybe a little too tight.

The synthetic was running cooler at 217 than the rd 20 50 running at 240.

Here's my question to Amsoil and their response below it.
Question:
Hi, I recently had my 75 Porsche 914 aircooled 2.0 liter engine rebuilt and have about 1000 miles on it. I first put in 20 50 regular oil for the first 500 miles so that my rings and bearings would seal and seat. The engine is running smooth and no oil leaks, but the engine temp is running at 240 degrees. I next put in Mobil 1 synthetic 5 30. The engine temp ran about 217 degrees which is ok but i wanted it to run cooler around 190-200 degrees.The engine was bored out to 103mm to a 2.7 liter size and has 78mm stroke. (stock is 71) I also replaced the fuel injection system to a SDS 4E and there is a mild cam in there. I would like your thoughts about using your (TSO) Series 2000 Synthetic 0W-30 Motor Oil in the next 100 miles. Is there another weight I should consider or will the 0W-30 be acceptable? Let me know if you have any questions so you can advise and I'll do my best to answer them. I'm not a mechanic but do understand a few things. Thanks Eddie

It is normal for an oil that is too thick to run at hotter temperatures as the thick oil makes the oil pump work harder, creating heat and the thicker oil does not transfer the heat as well. I think you will be pleased if you change to AMSOI< 0W30 oil, but do not try to keep the oil temp under 200-210 degrees as this will allow moisture to accumulate in the oil and contaminate it. (Above 200 or so, it boils off.)

Thank you for this opportunity to respond to your question(s). As always, please feel free to contact us again if we can be of further assistance.

Valve clearance?

NOTASIX · 09-26-2007, 03:39 PM

There is nothing wrong with an oil temp of up to 220F, I actually prefer my oil temps between 210 and 220 for many reasons.

There is more to an oil selection than simply the temps they provide, go to the LN Engineering site and read the article on oils that I have been assisting Charles Navarro with for the past 20 or so months.

Some oils today are liquid death to our vintage engines, so far the only oils that I allow to be used in my engines are Royal Purple Max Cycle and Brad Penn. I have mandated the use of Brad Penn in all my engines built pre 2000 and post 2004 not running composite lifters.

More than likley the guys at Amsoil won't be of much assistance- they do not work with aircooled engines daily and don't know the differences our engines have compared to watercooled counterparts as well as they should- no oil company does.

p914 · 09-27-2007, 10:51 AM

So I tried Amsoil 2000 synth 0W30 and it runs at 240.
I put the Mobil 1 synth 5-30 back in and it runs at 217 again.
I'm thinking a synth 5-30 or maybe even a 10-30 will be the ticket for now.

Tobra · Tobra's Garage

If it is a fresh rebuild you should check the valve clearances again, it is not that much of a PITA and could potentially save you a world of hurt.

I like regular oil in air cooled cars, but am sort of wasteful and will do changes q2000-2500. I figure it is doing more than just lubricating so it gets burned up carrying away heat. I don't drive it enough and am doing it by time over mileage. (Just paid some bills, so that is changing soon)

Synthetics don't burn up as fast, more refined, if you think about how they make it. Like the difference between a drum and disc brake, fully machined vs hunk of steel, so to speak.

p914 · 09-28-2007, 07:08 PM

Quote:

Originally Posted by Tobra

If it is a fresh rebuild you should check the valve clearances again, it is not that much of a PITA and could potentially save you a world of hurt..

Thanks
Just had the valves adjusted a week ago and they weren't tight at all. Clearances were good and in all was in good shape. I'm going to run it without a cooler if the synth 5 30 keeps that temp at 217. I think that's optimal right now.

Tobra · Tobra's Garage

The stock system is more than adequate for the car, you doon't need an external cooler IMHO, unless you have changed some things to get more power. If you go from 95 to 195 hp you will be making more heat, thermodynamics thing of some sort...

p914 · 09-29-2007, 09:30 AM

Quote:

Originally Posted by Tobra

The stock system is more than adequate for the car, you doon't need an external cooler IMHO, unless you have changed some things to get more power. If you go from 95 to 195 hp you will be making more heat, thermodynamics thing of some sort...

Read the first post it tells you some of the mods we did. It's probably about 150HP now or more.