Quote:
Originally Posted by Rekraps
Also, and this will cause a tremendous amount of heartburn with my fellow 1M owners, the need to change oil, or interval, is nowhere near 5K miles unless you are running the car hard (tracking). For years I used AmsOil synthetic in my heavy duty diesels and had the oil analyzed by the company. Assuming street use (yes you can drive it fast) and normal filter replacements at ~5K miles, the synthetic oil is still very good at the 20,000 mile mark. The whole notion of changing oil super frequently is just a waste of money, even though it makes us feel good. If you want to challenge this notion, submit samples of your motor oil for analysis. The results will surprise you. Synthetic oil is absolutely the best thing to ever hit the market.
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I hear what you say but past experience is really not a good indicator or case study on some issues. I have also heard people say things like I ran 30K mile intervals on my E90 328 and it lasted 200K miles. There are a lot of variables from viscocity, different grades of synthetic oils to lump all into a one category.
The biggest change from your past experience is that our cars are now direct injection. Just that fact alone nullifies past experience from port injected cars. The fuel is directly sprayed into the combustion chamber on top of the piston during the compression stroke. At this time the piston is low and the oil covered cylinder walls are exposed to a gasoline spray. The oil has to be able to withstand being diluted by gasoline and after combustion, the piston scrapes the oil from the walls along with any unburned fuel. Over time this unburned fuel mixes with the oil. The longer the interval, the more fuel that ends up in there. Another difference is that your diesel probably had an aluminum piston with a cast iron cylinder. Our cylinders use a newer process whereby metal is fused into the aluminum block. These are two variables that need to be accounted for.
There are many factors that come into play now. If the injectors get mucked up and are not atomizing, you could get more a spray on the walls and more unburned fuel. As rings wear, you get more blow by and fuel again to mix with the oil.
This is why Synthetic oil is so critical to direct injected motors. Organic oil would break down faster when mixed with fuel but synthetic can still dilute too.
So depending on the age and condition of the motor I wouldn't go as far as calling a lower oil change interval on a semi collectible car a waste of money.
Personally, I have my interval of ~7500 miles or 12 months whichever comes first on the 1M. On my normally aspirated port injected 330i running synthetic oil, I would go up to ~10K miles or 12 months whichever first.
Finally, the really tough part is this. Are you willing to run 15K intervals on your 1M for the life of the car and perform oil analysis and let us know how it goes at 120K miles? That would be great way to validate that it's a waste of money. Personally, I'm not willing to do it on my 1M because direct injection is relatively new on BMWs with the first ones coming out about 12 years ago. So we should start seeing pretty soon how these cars hold up with 15K oil change intervals. We probably won't see it among 1M owners but among the general population of 335i and X35i cars as they hit 120-150K with regular owners that used 15K mile intervals. You might eventually be proven to be correct that it makes no difference but that data is only coming in now as BMW engines with DI and new cylinder lining are reaching old age. But 8 years ago and even 3 years ago, i was not willing to go with 15K interval with my baby because of these two key variables that are often overlooked.
I am rooting for you to be correct but I will not feel I wasted money by being prudent based on the data that was available in the past. Just like when I had to buy powdered formula for my infant son. I went to Walmart in the middle of the night to get regular Similac but right next to it, they had Similac Plus! Man, I agonized....maybe if I go Similac Plus that might make the difference? So I went Similac Plus.... I probably wasted a few dollars but don't feel foolish for trying.
So fingers crossed!!!