Not "dirty" as in blowby and sludge buildup. There will be moisture condensed in it, and there are some additives that wear out based on a combination of time, heat, and mileage. Once the oil has been hot from a single drive cycle, some of those additives start to break down. Moisture will be a bigger problem if you do mostly short-trip driving where the engine doesn't see much mileage once it's fully warmed up. If you remove the oil cap and find water droplets on it or a white, cream-like substance, that is water and you need to spend more time at highway speeds. That water does not lubricate engine bearings and cylinder walls.
Another point to keep in mind is there is going to be blowby past the piston rings, and those hydrocarbons result in sludge in the oil. The only effective way to reduce that is by driving at highway speeds for a sustained period of perhaps 20 to 30 miles. That gives enough time for the hydrocarbons to vaporize and be drawn out and burned. Sludge will tend to melt too and get carried away by the oil and deposited in the filter.
Related to that, pistons in particular, and some other internal parts do not fit properly when the engine is cold. They have to heat up and expand, then they fit very precisely as designed. That's why 99 percent of internal wear takes place when the engine is warming up. It's also why you'll find very high-mileage engines of any brand when they're used extensively for highway use. Most blowby occurs during the warm-up period, so when the dealer heard you say how little mileage you'll be putting on every year, they legitimately want that oil changed much more often than what is recommended for normal driving.
My first concern is the 5,000 mile intervals. That is reminiscent of what Ford pulled in the late '80s with their advertising. They listed their oil change intervals at 7,500 miles to make their cost of maintenance appear to be lower than that of their competitors. It wasn't until after you bought the car that you found out all the deceptive things they pulled. That 7,500 mile interval was only for "normal" driving conditions. If you drove on any dusty roads, in rain, at highway speed, at slow speeds including city stop-and-go driving, or any short trips, you fell under the "severe use" category, and the standard 3,000 mile oil change interval. It was not possible to meet the conditions for "normal" driving.
I have a '93 Dodge Dynasty on which I plan to change oil every 2,500 miles because I drive it very seldom, and never in winter. It will be due for its second oil change in 1,200 miles, which should be in the next four or five years! This is just as hard on oil as the stunt I've been pulling with my '88 Grand Caravan daily driver. That oil hasn't been changed in over 13 years and 80,000 miles! This is obviously abuse, but there's more to the story.
The other thing you have to consider is the warranty on your engine and the things that are your responsibility to keep it in effect. This is part of what a high-level national trainer calls "customer-friendly business practices". Every manufacturer has their own requirements on what you must do. According to the instructor, Hyundai, Toyota, and Chrysler were at the top of the list of manufacturers with customer-friendly business practices. I know from working at a Chrysler dealership there was no requirement that you had to have the oil changed by the dealer to keep the warranty in effect, but not all dealers will tell you when that is the case. GM, VW, and BMW are at the bottom of the list, and while I don't know this for a fact, based on all the other ways GM has found to separate owners from their money after the sale, I would suspect they DO require you to go back to the dealer for oil changes so they can prove the maintenance was done. They have so many other tricks to force you to go back to the dealer;... I doubt they would let this legitimate reason slide.
In years past it was also common for dealers to want to do your first oil change so they could check for metal chips and other signs of pending problems. I don't remember hearing that at the dealership, but that might be an excuse you are given. The oil comes out too hot to touch, and any metal chips are just going to end up in the "drainmobile" along with all the other gasket material and gunk. Metal chips would likely go unnoticed anyway.
Early engine failure today is very uncommon on almost all car brands, yet, if that were to happen to your vehicle, wouldn't it be nice to have all the required oil changes documented in the dealer's records? If warranty coverage ever becomes a battle between you and the manufacturer, and the dealer thinks you're right, they're going to be your advocate in the argument, and that carries a lot of weight. Chrysler allocates warranty dollars to every dealership every year for paying for repairs that technically aren't covered by the warranty, or the car is just out of warranty. The dealer has sole discretion on whose bills get paid and whose don't. You know they aren't going to waste those limited funds on crabby customers who have unreasonable demands and aren't going to be satisfied no matter what. My dealer spent those dollars on good customers who had a problem that really shouldn't have happened. I don't know where Nissan sits on that customer-friendly business practices scale, but as a general rule, while they are on the lower end of all Japanese manufacturers, the Japanese overall are typically near the top, and European manufacturers are way down at the bottom.
I suspect too, if you look at the maintenance intervals in the owner's manual, they will list oil changes and many other things as "XXX miles OR XXX months, whichever comes first". Since they're offering to do this service at no charge to you, take advantage of their generosity and follow their recommendations.
Wednesday, March 25th, 2015 AT 7:06 PM