Bored and curious

[hooligan24]

On another car forum there was a thread started about spun rod bearings. The motors in question are modified and built/tuned Turbocharged 2.4L's in the Neon SRT4. Most were in the 350-420hp/400+tq. After a bunch of people were trying to figure out what caused the problems, I decided to ask the question, "what oil were you using?" The 1st two responses were "Mobil 1 5w30". I for one wouldnt use M1 5w30 in a 400+hp 4 cylinder motor, but that is just my preferrence.

I try to choose ACEA A3/B3 API SL/SM motor oils in my mostly stock 2.4l. Was I wrong to tell them that M1 5w30 isnt the right choice for these high HP/TQ motors? I tried explaining the HT/HS ratings and showed them the break down of the different ACEA specs, but they continued to tell me that the oil had nothing to do with their spun bearings. I also got the, "well, my 500hp cobra did just fine on M1 5w30 back in the day", "oil had nothing to do with it" answers. I tried telling them at a minimum, they should be using an ACEA A3/B3 with an HT/HS of 3.5 or higher. I then recommended M1 0w40-5w40, T6 5w40, M1 high mileage 10w30/10w40, Redline 5w30-10w40, and GC 0w30.

Am I right to think that the M1 5w30 wasnt up to the task of the extremely high pressures and probably caused the spun bearings?

Another note: their data logging showed nothing out of the ordinary when the spun bearings accured. Tunes were in check.

 

[addyguy]

Hard call.

Like you, I wouldn't use something as thin as M1 5W-30 in a modded 400-HP 4-cylinder - I just wouldn't trust it. Also, I believe there HAVE been issues with turbo Subaru(?) engines spinning bearings with M1 5W-30, but don't quote me on that.

On the other hand, lots of HP turbo/supercharged engines use M1 5W-30 w/o issue - the 260HP Ecotoc turbo in the Cobalt SS, and the supercharged 632HP 6.2 V-8 in the Corvette come to mind.

It will probably come down to an individual issue with each engine, not a general trend....

 

[d00df00d]

Doesn't that car spec Mobil 1 0w-40?

 

[gathermewool]

+1

I think it has more to do with the engine and how it was driven, though oil can't be fully relieved of responsibility. I also think that most (at least those out of warranty) will quickly fess up to things like running the sump low, over-reving, etc; however, there are always those who will say that they had done nothing out of the ordinary to cause failure. All we have to go on is some one's word and, depending on their status on the forum, that's usually good enough.

Spun rod bearings have and do pop up on the Subaru forums every so often. A lot immediately attribute spun bearings, cracked ring lands, and excessive oil consumption to the use of M1. While I myself wouldn't ever use regular M1 5W-30 in my turbo Subie, there are plenty who do and have with out any incidents over many miles.

My guess is that M1 is adequate for a DD or even moderately spirited driving, but may not hold up well when pushed to its limits in a stock or modified engine. As far as oil consumption, who knows. I think a motor that consumes oil will consume no matter the oil, in most cases. A less volatile oil might go longer between adds, but motors, IMO, don't gulp and then sip after changing oil brands.

 

[hooligan24]

stock engine specs 5w30.

just curious, is those 632hp corvette specs at the flywheel or to the wheels? Almost all SRT4 owners get power to the wheel readings.

Not saying M1 isnt up to the task at, just trying to learn more.

I used this explaination to the "500hp cobra" guy.

500hp cobra:
62.5hp per cylinder (500/8)
100-108hp per liter. (500/4.6 or 5.0)


For the Vette:
79hp per cylinder (632/8)
102hp per liter (632/6.2)

400hp Neon
100hp per cylinder (400/4)
166.6hp per liter (400/2.4)

I dont know if it correct to assume, but to me it looks like the 4 banger would be seeing higher pressures and stress compared to the other beast's