Switch from 5w30 to 10w40

[mrKiKaZ]

I want the definitive answer to whether it is okay to switch from the manufacturer recommended 5w30 to a 10w40 motor oil?

I recently put a turbo on my 2006 Scion TC and plan on tracking the car, should I switch to 10w40?

I'm sure this topic has been discussed several times, I've read that due to the tight tolerance and clearance of modern engines that it is best to stick with what the manufacturer recommends, however the car now has a turbo... please clarify for me. I have noticed the oil pressure at idle when completely warmed up has dropped about 2 psi. Currently using a 10w30 synthetic oil.

Just FYI, I also used to be supercharged and always used 5w30 with great success, however usually with my oil analysis reports, it would come back that the 5w30 oil has sheared down to a 20 weight oil.

 

[A_Harman]

Does the turbocharger have a water-cooled bearing housing?
How much boost are you running?
Has the engine been modified internally?
Is there an oil cooler on the car?

Switching from 5w30 to 10w40 isn't necessarily going to give you better protection. 10w40's in general are just as prone to shear as are 5w30's. For turbocharged gasoline engines that get track use, you need an oil that is highly resistant to shear and oxidation, and can handle a turbocharger heat soak in case of a hot shutdown. In cases like this, I like Red Line 5w30. It has the HTHS of a light 40-weight oil.

 

[mrKiKaZ]

No water-cooled bearing housing.
6.5 psi
Stock motor
No oil cooler currently, I do have one from when I was using a supercharger, need to work on extending the oil lines as the charge pipe for the intercooler is now in the way.

I really like Motul's racing motor oil, how would you say Redline compares? I like how you say it's like a light 40-weight.

 

[A_Harman]

I think the Red Line 5w30 will work fine for a low pressure turbo on a stock engine.

Red Line & Motul are both ester-based oils, and are similar in specs and performance. Redline is made in California and is cheaper less expensive.

 

[mechtech2]

Monitor the oil temperatures.
When using boost, the turbo'd engine will get hotter.
Normal driving can use the 5-30, but for track and hard driving conditions, ane X-40 will probably be needed.
Mobil 1 0w40 is an excellent turbo oil.

BTW, there is no "the definitive answer".

 

[bourne]

Before you switch to 10w40 how about you give rotella t6 5w40 a shot in that engine.

 

[mrKiKaZ]

Originally Posted By: A_Harman
I think the Red Line 5w30 will work fine for a low pressure turbo on a stock engine.

Red Line & Motul are both ester-based oils, and are similar in specs and performance. Redline is made in California and is cheaper less expensive.


I've heard great things about Redline and I did check prices, definitely cheaper then the Motul racing oils, will definitely give it a try, so you feel the 5w30 is suitable for track use?

Originally Posted By: mechtech2
Monitor the oil temperatures.
When using boost, the turbo'd engine will get hotter.
Normal driving can use the 5-30, but for track and hard driving conditions, ane X-40 will probably be needed.
Mobil 1 0w40 is an excellent turbo oil.

BTW, there is no "the definitive answer".


Sad to say that I don't have a oil temp gauge, I already have so many gauges installed, really wasn't looking forward to installing a oil temp gauge. It wouldn't be easy as I would most likely have to tap my oil pan, I'm already using an oil filter sandwich plate to run my oil cooler lines.
I am sure 5w30 would be suitable for daily driving, still devided on whether to use a 40 weight for track use. I really wish there was a definitive answer.

Originally Posted By: bourne
Before you switch to 10w40 how about you give rotella t6 5w40 a shot in that engine.


I've heard great things of Rotella's 5w40, I believe a lot of subaru guys use it.

 

[bluesubie]

Originally Posted By: mrKiKaZ


I've heard great things of Rotella's 5w40, I believe a lot of subaru guys use it.

That's because it's robust, cheap, and you can get it from Wal-Mart. 5W-40 was also the requirement in the owner's manual in severe conditions up until 2010. Many were using German Castrol (Syntec 0W-30) but it can be hard to find, depending on your location, and you have to catch it on sale.

Any 30 weight that is not Resource Conserving is usually more stable. I would probably go with a robust 30 weight in your application instead of a heavy 40 weight.

-Dennis

 

[A_Harman]

Yes, Red Line 5w30 is suitable for track use. I've run it in my Camaro on track for a season without trouble.

Mobil 1 0w40 is also a good oil, and has manufacturer approvals for turbocharged engines.

RedLine 5w30 and Mobil 1 0w40 spec's:
HTHS: 3.8 3.8
Flash Point: 252 C 230 C

The HTHS spec is the critical one to look at for track use. It gives and indication of the film thickness at high temperature and shear stress conditions. Since HTHS is the same for the two oils, they will give the same film thickness at high temperature conditions.