Here is a post from techspeak on the other forum..I dont know enough about oils so Ill just let you read it.I hope he dont mind me pasting it here..he seems to know what he is talking about.
Techspeak
Having people tell me what I'm qualified to- and not to- say is not really a good way to get me to open up. Asking me for clarification would have probably worked better.
That said, that list of car manufacturers comes directly off of Mobil's website. Note the wording "Mobil 1 technology has been selected as original equipment.." the "technology" sure, the viscosity grade, no way! Mercedes AMG and Porche for sure would never put 5w30 in their engines, ever. That line is purely a joint marketing strategy and nothing more.
In my experience, Mobil 1 30wt's (5w30, 10w30) tend to consistently show high Iron wear levels in oil analyses, because it's on the very thin side of a 30wt. In fact M1 30wts specifically tends to shear down to a healthy 20wt by oil change time. 20wt (9 cSt and lower) is BAD news for turbo's and the engines they feed. Oil shear happens when long-chain polymeric viscosity improver molecules break apart permanently. Thin EC oils with wide spreads (0w50 would be an example of a wide spread) tend to rely heavily on Polymeric VIIs to get that spread. Without VIIs in most modern EC 30wts, they would in fact be 0w5 weight oils. WAY THIN, but at least without the VIIs they would be shear stable. High heat and shear cause EC oils to drop in viscosity. All oils carry a HTHS specification (high temperature high shear). Energy Conserving oils are designed to meet a target economy rating, by producing less drag internally. The problem with these EC oils is they have low HTHS ratings because they are loaded with Polymeric VIIs. Automakers are pushing for the thinnest oil they can get away with now days, so that they can meet the Corporate Average Fuel Economy (CAFE) specified by the EPA. It's been a good and a bad thing. Good because it's forced oil slingers to increase the quality of their base oils and use better VIIs. They want to be sure that their cars can make it through warranty on 5w20 [or turbos on 5w30]) These modern 20 and 30 wt EC oils are just fine for the average consumer, low output, NA engine, but can be fatal to high output, high heat turbos and the engines they feed, especially when modified. So yeah, thats the bad part. Grab an owners manual from North America and one from Europe or Japan, for the same vehicle. The North American manual will say ONLY 5w30 (turbo) or 5w20 (NA) recommended. The EU/JP manual will show a wide range of viscosities, tailored recommendations for the ambient temp and operating conditions. Why the difference? The EPA and CAFE. SO to protect your investment as a turbo enthusiast here in NA, you'll need to know a little about your oil selection. Hope that helps someone
I forgot to mention one other very important thing about the DISI engine: fuel dilution.
During the end of the intake stroke, the direct injectors fire,and apparently there is a phenomenon in gas DI engines whereby fuel has a tendancy to adhere to the cylinder walls. Since the fuel enters the combustion chamber from high pressure, its latent heat has the cooling effect. This is good for atomization, but bad for vaporization. Remember the fuel doesnt sit on the hot intake valves and it enters the process much later than traditional port EFI, giving it significantly less time to vapourize. The result is that some fuel gets washed down the walls, past the rings and into the oil. This is becoming a prominant issue with turbo gas DI engines.
2-4% fuel dilution in the oil is commonly seen in used oil analyses for this engine. Normal engine fuel dilution is usually in the range of 0-1.5%. Therefore fuel dilution can be considered higher than average. Gasoline Direct Injection engines like the 2.3L DISI and the BMW 335i, have been just mutilating oils, from both mechanical shear AND moreso fuel dilution. After a lot of thought, I personally would use a non-synthetic 15w40 HDEO - Heavy Duty Engine Oil . 15w40 is designed for severe service, and is generally not marketed to consumers as a result. 15w40s are affordably priced (ie not a RIP OFF), extremely robust and can be changed out every 5K without a problem. It's low content or absence of VII's can handle high fuel dilution better than even most common synthetics! In fact I invigte anyone to run one oil change interval of M1 5w30 and then one run of any 15w40 and compare the used oil analyses! I would honestly put money on the 15w40, without a doubt. The similarities between the DISI engine and a diesel are striking. Both are subject to high fuel dilution due to DI, both experience very high crankpin forces PER rod journal and have high temp turbos.. the exact conditions 15w40 was designed for. If it's not winter where you live, you change your oil every 5K and you have lots of mods on your 2.3 DISI, then 15w40 is THE smartest choice IMO. That said, it's time to pander to implanted psychologies; I know people have bad psychological associations with 15w40 and non-synthetic oils, so then lets talk synthetics.
"Synthetic" as a word used in the oil industry means very little
There are 3 main types of "synthetics".
Group III - Now the most common type of "synthetic", these oils are what Castrol Syntec got a bad rep for being years ago, very highly refined crude oil. They call it synthetic because they think it's no longer mineral oil because it's been refined so much. In reality, it still is mineral oil... just highly refined mineral oil. The high prices, however remain the same, because now highly refined oil is called "synthetic". Mobil 1 had gained a lot of ground by playing on Castrol's while they continued to tout themselves as PAO synthetic. Guess what? Mobil has slowly switched over their common EC consumer grades to Group III base stocks The price hasnt budged. The consumer thinks that since he's still paying more, it must still really be synthetic. What they don't know is that the oil's have fractioned in cost to produce, but still retail for the same exuberant price. It's rumoured that Mobil 1's heavy duty grades are still PAO. No GC test has been done on those grades though. Pennzoil Platinum hasnt been too bad in the DISI engine, interestingly.
Group IV - Real syntheitc! PAO. Polyalphaolefins. One of the older, common synthetic fluids. This is what all Mobil 1 and many trusted names used to be. This is what AMSOIL, Royal Purple, Lubro-Moly and most European oils are. PAO oils are not as cheap as Mobil 1 or Castrol Syntec (or Pennzoil Platinum, or Q-[insertnamehere], or Valvoline Synpower ... hmm funny how all the most trusted names are Group III... great way to exploit that trust huh?) That is why the little guys oil costs more, because they havent sold out with a cheaper formula at the same price yet.
Group V - includes all other synthetic fluids, including not so common ones. One of the major Gr V oils is POE or Polyol esters. These are some of the best, most expensive oils to make. This is what Redline is made from mostly, thus the price. As it's still priced slightly higher to M1 per quart, Redline costs well over twice as much to produce per quart. Redline 5w30 would easily outperform mobil 1 0w40 at 'emergency' temperatures. That speaks volumes about base oils.
How does this apply to anything? Well my estimation is that energy conserving, low HTHS, low cSt oils ("synthetic" or not) are being shredded apart in DISI turbo engines, being mechanically sheared as well as diluted in fuel breaking it down. As the fuel diluted woefully inadequate lube hits the turbo bearing section, it hits the hottest section in it's travel, breaks down completely at this point where it seeps past the turbo seals and continues to cook in the exhaust gasses. The result is sludge and exhaust smoke, much of the smoke burned off further by the cat (if still installed) or just going out the back without a cat.
If you're smoking or consuming oil, get RID of the thin Energy Conserving oil! Try 15w40, you will not be disappointed! If 15w40 sounds too gross, then try any "European formula" synthetic oil. They come in 5w40, 0w40, 10w40. Many are duel rated for gas/diesel. A good oil for this app can also be identified by ACEA A3 rating. You'll notice that some PAO oils, even 0w30 will have ACEA A3 rating, but Mobil 1 5w30 wont, even though the 0w30 has a wider spread. Again that speaks volumes about base oils used and the oil's performance.
sharkdriver - If you had to stick with M1, go with the 10w40. Should be slightly more shear stable than the M1 5w40
diablospeed - 5w40 is just fine, a perennial fav. among the euro boys. all else equal 10w40 should prove more shear stable.
javanc - PP 10w40 would be just fine. Even though PP is a Group III, it has performed above average for a GIII and they don't charge as much as the competition for GIII
predator - 5w40 shouldnt be so hard to find. It's worth the search though, especially if you do get a UOA on the 5w30... I'm not psychic but the Cu and the Fe will be elevated, i can tell you this now
smakdown - yes AMSOIL has recently added a 5% surcharge to their orders. I wont say anything about that price, but at least they'll sell you a PAO Gr IV oil
But to all you guys who arent in winter now, I still highly recommend 15w40... it's tough oil, designed for the condition, designed for industry by industry, tougher add pack than any consumer API SM oil and it's not "consumer" priced (not a rip off)... doesnt get any better than that IMO! Do back to back UOA and convince yourself!
