PegasusCapital

The January 2017 issue of Corvette Magazine has an excellent article about the direct injection system in the C7 LT1 and LT4 engines. It does a good job of explaining how the DI system works and what the benefits are. There is also a good discussion of valve coking and what GM has done to eliminate/minimize the problems. (This should re-open the ongoing, never-ending discussion regarding catch cans.) Finally, there are recommendations from GM regarding the use of Chevron Techron and a special synthetic oil I never heard of.

jdarc1

Where can I get this issue ?

ExRedRacer

Thanks for the tip. Interesting article.

jdarc1...You can find it online.

Patches

https://www.corvette-mag.com/issues/...n#.WCuLzE0zWUk

jdarc1

Very interesting article indeed.

Maxpowers

Very interesting!

Cirrus8

So, who knows what the NOACK rating is for Mobil 1?

Patches

Approx. 9% by weight (5W-30)

propete

Nice article , thanks for sharing the link.

ExRedRacer

From the article:

"....you need an engine oil with the lowest NOACK rating you can find. The NOACK test is a measure of an engine oil’s volatility. The lower the NOACK, the less likely it is that the oil will coke and form deposits.

With that in mind, consider a full-synthetic oil that exceeds Dexos requirements. An example is Driven Racing Oil’s LS30, which has a lower NOACK number than Dexos mandates and is the only premium, full-synthetic oil formulated specifically for GM Gen III, IV and V V-8s with cylinder deactivation and cam phasing....."

What's the NOACK rating of Driven racing Oil LS30?

Zymurgy

From the Petroleum Quality Institute of America:


ASTM D5800 - 08 Standard Test Method for Evaporation Loss of Lubricating Oils by the Noack Method

Noack volatility determines the evaporative loss of engine oils. This test is important because the operating temperatures of an engine will typically drive off the lighter ends of a lubricant while in service. This effectively results in increasing the viscosity of the lubricant to a more viscous (thicker) level and, as a result, fuel economy goes down due to an increase in parasitic load.

The evaporation loss is of particular importance in engine lubrication. Where high temperatures occur, portions of an oil can evaporate. Evaporation may contribute to oil consumption in an engine and can lead to a change in the properties of an oil. Oils failing to meet the volatility limits will struggle in many oxidation tests including the sequence IIIG engine test which is a critical and sometimes formulation defining test. This test is impacted by many factors including the Noack volatility. Anti-oxidants can improve oxidation control but cannot prevent evaporation of the base stock leading to rapid oil thickening.

Tron1

Had my 1st oil change (at 2370 miles) 3 weeks ago, and used Pennzoil 5w-30 Ultra Platinum, Dexos certified, instead of Mobil 1 5w-30 mostly because of the 6.6% NOACK to reduce the oil coking of intake valves. I have not yet purchased a catch can due to possible warranty issues.
I read the article in Corvette mag but it did not specify the NOACK number of Joe GIbbs LS30 oil.

Tron1

According to the PQIA the NOACK of Mobil 1 5w-30 is 10.1%

Seadawg

They lost me in the article by recommending Tier fuels to help with valve step coking. Fuel never should get to the valves stems in these engines, should it?

What am I missing?

Foosh

Just found this reference, which may be of use to some.

Foosh

You must have missed the section that suggests the LT1 design provides some fuel back wash.

This is one of the most encouraging articles I've read, and it made me feel more confident that GM engineers were keenly aware of the need to address the DI valve deposit issue.

ExRedRacer

Very informative.

I guess I'd be more impressed if the study had been performed by an independent lab instead of being done by Amsoil, whose oil just happened to perform the best in most tests.

EDIT...Never mind.

I just reread the article and the tests were indeed performed by an independent third-party lab. Now excuse me while I go look up my nearest Amsoil distributer.

Foosh

ExRed,

On page 2 under "Methodology," they say, "Testing was completed February 2013 by an independent, third-party lab." At any rate, Mobil 1 is one of the better performers in all tests, but one.

Mobil 1

The Mobil 1 was the "extended performance" version. Would like to see the difference with the regular Mobil 1.

Foosh

Amsoil Signature Series is not a Dexos-approved oil. Hmmm . . .