Hello 348 brotherhood, For a while now, I've been having a problem with a small oil leak from the rear corner of the valve cover. I've been delaying tearing into the valve cover and the gasket job as it was an isolated leak and, frankly, I was too busy (and probably lazy) to tackle this. Anyhow, I noticed that the leak completely stopped after switching from Mobil 1 to the Shell Rotella T6 5W-50l. I cannot explain why this happened but I will tell you the engine seems to love this oil. I used to run it many years ago in my Audi A4 with great results and I'm glad I "rediscovered" it. I can also tell you that the engine seems to idle smoother and is quieter. To sum, up given the price of the oil and the results, I am probably going to stick with it as the default oil for the 348. If you are getting a seepage from valve cover gasket I suggest you try this oil as you may find it a cure like I did. Bart
The diesel oil right? I also run this in my 986 Boxster. IIRC it also has a high level of ZDDP which is necessary for our flat tappet cams. I don't like the idea of running a thicker oil just to cure leaks, IMO that just masks a problem, but there are other reasons to run it, and you are right that the thinner synthetics like the Mobil 1 recommended can exacerbate leaks as its easier for it to sneak past seals. I haven't had to do an oil change in my 348 yet, but I was planning on using this oil as well.
I think technically yes, the Shell Rotella T6 5W-40 is a "diesel" oil although I have heard about many people using it in gasoline applications with great results. BTW, there is a typo in my post. The oil is 5W-40 not 5W-50 so I did not put a thicker oil than, I think is specified.
Looking back through my records, my car has had Shell Helix Ultra 5W40 synth for at least since 1999.....it’s dry as a bone, no leaks at all. This is a European oil but some US places do sell it, including ECS Tuning (Audi/VW parts house). $36 for the 4 liter container. I’ll probably continue with this over time, but I’d be curious how different this is from the Rotella. https://www.ecstuning.com/b-shell-parts/helix-ultra-5w-40-synthetic-engine-oil-4-liter/550040755~shl/?gclid=EAIaIQobChMI6Pr73I-52wIVAcZkCh3m1gSrEAQYASABEgJILfD_BwE
Thanks for sharing, although high ZDDP, the shell rotella doesn't look particularly good in those test results. I use gulf competition and although the ZDDP levels aren't published it has really good test results on that blog.
One thing we should be careful about when finding info on ZDDP content (published or determined during an analysis) for any oil is what year they come from. ZDDP has been gradually reduced over the years so its content today will probably not be the same as, say, in 2014. One example is Shell Rotella T6 5w-40. The ZDDP content of this oil changed as follows (results of oil analyses, attached): 2014: Phosphorus 1157 ppm, Zinc 1310 ppm 2017: Phosphorus 1049 ppm, Zinc 1095 ppm Here's a picture of new (current) and old (~2015) Rotella-s T6 5w-40. So, if you can find the older stock, that Rotella will be fine; the new one? - I wouldn't use it in a flat tappet engine. Image Unavailable, Please Login
This might just be fuel added to the oil fire, but I have had similar oil usage/consumption issues in a turbocharged car and Mobil1 in 5W-30. At one point on a 45k mile engine, I was using 1.5 of 4.2 quarts in the engine in 3k miles. Once switched over to anything that was not synthetic, the oil consumption slowed down and then stopped all together. Interestingly, Rotella was also nominated as an oil to rectify this situation on this engine with mixed results. I have also had exceptional results with Mobil1 on a different vehicle (no oil usage, no leaks, inside of motor looked brand new at 125k, etc.), so this is not merely 'Mobil1 hatred'. This is a subjective opinion, but I think that the uniform oil molecule sizes of synthetic (while great for start up lubrication and tiny oil passageways) lends itself to exacerbating existing leaks and finding its way past solid seals (like the brass/bronze bushing oil seals in a turbocharger) leading to consumption. I have also read many anecdotal examples of oil leaks that were 'solved' merely by switching away from synthetics.
I also use Shell Helix Ultra 5W40 but with a +- 800 ppm ZDDP additive ( Cam Shield). My engine runs like a Honda engine. I think most modern oils are around 800 ppm ZDDP now.
The amount of reading on that blog is huge, especially if you get into his Q&A section. But ne thing he reiterates often is that ZDDP content has no real world correlation to his test results— he’s rated some low ZDDP oils highly and yet some high ZDDP oils are way down the list. Of course, you have to decide whether or not you buy into his methodology. The more I read, the bigger believer I’ve become. I wish there was a group effort behind the testing, but on the other hand I don’t know of anyone else who’s doing what he’s doing, and after reading a lot of what he’s written I don’t think he’s shilling for any particular oil company. And honestly, what he says makes a ton of sense, even though it doesn’t follow the stuff espoused on sites like Bob is the oil guy. But then again, I’ve never seen any of the self-proclaimed authorities on that site referencing their own quantitative research. Downside for me is I’ve got a good bit of Rotella T synthetic around for a couple of my street cars that I’m now wondering if I even want to use...
He spends half the time espousing how he’s right and the world is full of doubters. haha. Odd writing style too. I wish he’d stfu half of the time. Interesting research though.
This phenomenon is discussed quite a bit on the blog I linked above. He recommends conventional oil as a means of reducing oil consumption. Your experience is shared by a number of people who’ve written in to his Q&A section. According to his current ratings, Mobil 1 0W-40 is very, very highly rated, and Mobil 1 in general does pretty well. But some engines seem to burn a lot of oil when synthetic is used, in which case conventional oil often reduces consumption markedly. I don’t think there’s anything contradictory in that— it’s just a matter of finding the best oil for a given application.
The sealing issue could be something to do with the compatibility of the sealing materials with a given oil composition. I was reading another article earlier today I'll try and dig it out again.
