DrKFM

I understand the CD requires oil changes and top off of Adblue every 5K. Since it is based on the same engine as the Volkswagen and Audi I do not understand why the increased number of services. Those vehicles requires every 10k as does the European maintenance schedule for the Porsche CD. That last document appears when you Google the CD

Any thoughts?

Needsdecaf

Been discussed. Likely Porsche's fear of liability due to IMS failure and other issues.

fincher

Porsche is likely concerned because diesel fuel in the US is not of the quality found elsewhere. I use 8oz of Power Diesel with every fill up on my Touareg TDI. No issues. Lots of discussion, debating and oil analysis, etc. on various forums.

grohgreg

An important quantifier that puts our diesel fuel in the "low quality" class - is cetane. The cetane rating is in indicator of how complete the fuel will combust. The higher the cetane rating, the more complete the burn. Our diesel fuel cetane is typically rated in the 40-45 range, with an occasional offering of up to 52 in very selected areas. That said, it's a globally accepted fact that diesel engines operate most efficiently on 50 and above. In some places it's refined with as high as a 60 rating.

When the burn is not complete, particulate matter is left behind. Hence the particulate filter in our exhaust systems. Those particulates are what still come out of older diesel exhaust as black smoke, and leave dirty residue on tailpipes and bumpers. Particulates. In newer diesels, particulate filters trap this crap, which periodically gets burned off with injections of DEF (AdBlue) and diesel fuel.

But here comes the part that I don't quite understand yet. It is said that small quantities of that diesel fuel works its way back to the oil pan, diluting the engine oil. Just how much and how fast varies with the way the car is driven; slow urban driving makes the particulate system work harder than fast freeway driving. But for warranty and liability reasons, Porsche defers to the worst case scenario. Hence, the 5000 mile oil change.

I do very little urban driving - plus I add Power Service to boost the cetane rating in the fuel tank - so the 5000 mile interval is likely too short for my CD. My plan is to change at 5000 as recommended, and send a sample of the used oil in for testing. The cost of the test is no more than a 2-3 quarts of C30 oil. From the results, I will then have a basis upon which to customize my own oil change interval.

Regarding the AdBlue top up; usage rate is also tied to how the car is driven. Slow urban driving uses more than fast freeway driving, the latter often yielding 15,000 miles and more from one AdBlue tank. My last car used AdBlue, and by 17,000 miles I still hadn't added a drop. So technically you can drive until the car gives you the "AdBlue Low" alert, at which point you still have about 700 miles worth left in the tank. But Porsche again goes worst case, recommending you top up the AdBlue tank at each (5000 mile) oil change. I too will top up, but only at whatever interval my oil test results dictate.

//greg//

gnat

Your only issue there is your warranty. They can't void it for not having the dealer change the oil (one of my locals wants 625!!!), but they can void it if you can't prove that you had it done according to their guidelines.

I agree 5k is ridiculously short for synthetic, but as long as the warranty is in effect (and you care about it) then you need to change it that frequently regardless of how good it still is.

Unless/until they change their guidelines again.

grohgreg

Your argument has merit, were it not for the oil analysis results. Given the cost - compared to that of C30 oil - the tests will pay for themselves in oil/filters not used. Plus they constitute black and white documentation of the state (and date) of the oil removed. Besides, I'm hoping Porsche is working behind the scenes to update the engine oil quality sensor system for US-spec CDs that will accommodate the lower quality of our fuel.

//greg//

Needsdecaf

Greg, what's the cetane additive that you use? Have you been using it since day one?

fincher

I will chime in if you don't mind... I use Power Service white bottle in the winter and the silver bottle the rest of the year. There are other brands such as Amsoil, etc.

Greg is a knowledge guy and I remember his contributions over on Club Touareg.

DrKFM

Newbie to the board. You guys are awesome,,,,what got me going was the 395 for the 5K service and 485 got the 10K and I am good for 15K a year, But what needs to be done needs to be done, The porsche plan is 2900 for 3 yrs 40K and looks like it is priced right as long as you keep the car.

grohgreg

Power Service, used it for years in 4 cars and 5 tractors. Getting a diesel generator tomorrow, will use it there too. White jug in winter only (contains anti-gel component), silver jug during the other 3 seasons. That said, Amsoil has recently introduced a cetane booster, I'll be test driving that as soon as I buy some.

//greg//

Slow Guy

Curious as to how you would know that the cetane additive is actually boosting the cetane. Is there a (consumer) way of testing it? I know next to nothing about diesel but my thought would be it's more a refining issue than a lack of additives issue.

Hopefully vehicle mfgrs are pushing the oil cos. to improve the quality of their fuels but considering the stink being raised over the push to lower the sulfur in gasoline I'm not sure it will have much effect.

grohgreg

You are correct, it's a refining issue. Most of the #2 diesel in this country has a 40 cetane rating. Cut rate stations and truck stops pretty much sell it just the way it comes off the truck. Name brand stations like BP, Shell, Exxon, et cetera likely use additives in their underground tanks to bring up the cetane number to corporate minimums. Amaco stations are few and far between around here, Shell (46) is more common. To that I add 12 oz Power Service to my 26.4 gallon tank. That's supposed to add an advertised 5 numbers, bringing what's in my tank to an equivalent 51 cetane rating.

I copied the attached list from another turbo-diesel site, and carry it in the car for those days when there's neither a Shell nor an Amaco in sight. And I don't know of any consumer test to determine cetane rating. It would be nice if stations would put it on their diesel pump like they do octane on gasoline pumps. Until then I go on faith that this list is reasonably accurate.

//greg//

steve_Cayenne

Time to find a good Indie. Probably less than half the price, and warranty cannot be legally declined if they did the work properly per maintenance schedule. This is my first Porsche, but always used Indies on my last few BMW's and they were as good as the dealer. Even had thick German accent to boot, don't find those kinds of mechanics at a dealer

All due respect grohgreg, although you may well be technically correct in circumventing the shorter maintenance schedule by using cetane additives, and monitoring oil quality results ... I would happily decline your warranty claim in the off-chance case of an engine failure, if I worked as a bean counter at Porsche

gnat

The issue, however, isn't one of the date (unless you are an ultra low miler) or oil quality as far as the warranty terms go. The terms are based on you following the MFG recommended service intervals.

I'm all for fighting for the principle of something and I think if it you had such documentation for every oil change you could probably win a legal battle over them trying to void the warranty on the engine, but that's a lot of headache and pain compared to just changing every 5k until the warranty is no longer valid.

Now using such information in a class action against them given what dealers charge for an oil change (as most owners will just let the dealer do it for various reasons) and that the same engine in the Cayenne's siblings have a longer interval might be a different story altogether. I'm not advocating anything though.

Slow Guy

Curious, around here all former Amaco stations were rebranded BP right after the merger (dumb move PR wise IMHO, I thought the Amaco brand had higher value for us in the US than BP and certainly after the Gulf fiasco). Just questioning how old that data might be.