At 28,066 dealer oil change. At 28,778 dealer flushed engine to remove sludge build up and changed oil. At 30,835 miles inspection, dealer flushed engine to clean out sludge and changed oil. At 34,630 miles sludge clogged PCV valvue. Oil level dropped by 1 to 2 quarts. Oil light flickered. I changed oil. Will this happen again. Oil changed at 3 to 6 thousand miles since new.

First, verify that there is no oil leakage at the new sensor. I've had that happen a time or two.

If that isn't the issue, it could be a worn oil pump, or general engine wear and internal oil leakage exceeding the pump's capacity to maintain oil pressure.

Another possibility is a build-up of debris (sludge) on the pump intake screen. It may be tempting to try an engine cleaner oil additive to remove sludge, but I've heard of too many people blowing up their engines doing that. Cleaners may be helpful for a small amount of sludge, but a large blob of loosened sludge going through the pump and into the oil galleries is bad news.

It may be time to drop the oil pan and inspect for sludge, and perhaps also check some bearings for excess wear. I'm not familiar with Nissan oil pumps, but those I've seen from other makes can be disassembled for inspection, or the service manual may provide specifications for replacement wear tolerances. (Service manuals are usually not cheap, but you may be able to get your local Nissan dealer service department to give you a copy of the relevant pages.)

A full tune up ; plugs, wires cap and rotor ( if applicable,) air and fuel filter.

There are two main causes for sludge, not changing the oil and filter at regular times, and not running the engine long enough to get it hot.
You might want to get a second opinion from a shop other than the dealer. The dealer may have a sales promotion on engine flushes this month.

I doubt you have sludge in your engine since oil has detergent in it to prevent this. I would stay away from this dealer.

do this the oil is turning black due to sludge build up in the motor. change the oil and filter buy 1 quart of rislone come in an quart bottle like oil use this in place of 1 regular quart of oil. drive for about 250 miles then change oil and filter again this will remove all sludge build up in your engine. then your oil will stay clean for a normal interval with out turning black.
i use this in any car i buy and it always works.

It's listed in your owner's manual. Schedule A is normal driving conditions.
SCHEDULE "A"
7,500 miles (12 000km) or at 6 months
- Change engine oil.
- Replace engine oil filter.

15,000 miles (24 000km) or at 12 months
- Change engine oil.
- Replace engine oil filter.

22,500 miles (36 000km) or at 18 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.

30,000 miles (48 000km) or at 24 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace spark plugs.
- Drain and refill automatic transmission fluid and filter (4.7L).

37,500 miles (60 000km) or at 30 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Drain and refill transfer case fluid.

45,000 miles (72 000km) or at 36 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.
- Flush and replace engine coolant at 36 months, regardless of mileage.

52,500 miles (84 000km) or at 42 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if not done at 46 months.

60,000 miles (96 000km) or at 48 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace ignition cables (5.2L/5.9L).
- Inspect PCV valve, replace as necessary.
- Replace spark plugs.
- Inspect auto tension drive belt and replace as necessary (5.2L/5.9L).
- Drain and refill automatic transmission fluid (4.7L).

67,500 miles (108 000km) or at 54 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.

75,000 miles (120 000km) or at 60 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Drain and refill transfer case.
- Flush and replace engine coolant if it has been 30,000miles (48 000km) or 24 months since last change.
- Inspect auto tension drive belt and replace if required.

82,500 miles (132 000km) or at 66 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if it has been 30,000miles (48 000km) or 24 months since last change.

90,000 miles (144 000km) or at 72 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace spark plugs.
- Inspect front wheel bearings.
- Inspect brake linings.
- Inspect auto tension drive belt and replace as necessary.
- Drain and refill automatic transmission fluid (4.7L).

97,500 miles (156 000km) or at 78 months
- Change engine oil.
- Replace engine oil filter.

105,000 miles (168 000km) or at 84 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if it has been 30,000 miles (48 000km) or 24 months since last change.
- Inspect auto tension drive belt and replace if required.

112,500 miles (181 000km) or at 90 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Inspect front wheel bearings.
- Inspect brake linings.
- Flush and replace engine coolant if it has been 30,000 miles (48 000km) or 24 months since last change.

120,000 miles (192 000km) or at 96 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace ignition cables (5.2L/5.9L).
- Inspect PCV valve, replace as necessary.
- Replace spark plugs.
- Inspect auto tension drive belt and replace as necessary.
- Drain and refill automatic transmission fluid (4.7L).

Thanks for using FixYa -a 4 THUMBS rating is appreciated for answering your FREE question.

I'm betting that this is the 2.7L engine. If it is, you may have caught this in time. There is a very good possibility that the oil pump intake has become plugged with sludge. You will have to have the oil pan removed so that the pick-up can be cleaned and the engine flushed out. After that you must use synthetic oil. This was a huge problem, lawsuits galore. Google: "2.7L sludge" for more info.

Sounds like you've got sludge. The best way to deal with it is to change the oil. Flushing with an oil cleaner is dangerouse but faster. The cause of this isrunning too long without an oil change, engine overheating, and antifreeze leaking into the oil. Lots of really short trips where the oil doesn't reach full operating temperture. Change the oil with a good cheap oil including the filter. Run the car for about a week 200 miles and change the oil again, filter and all. do this again untill when you go to change the oil it's not exactly black solid like the first time you changfed it. Another cause of sludging is the car does'nt warm up fast enough and not hitting the full operating temperture, it could need a new themostat. Overheating can cause problems too. Is the cheak engine light on? If it is you need to research the problems and get them repaired because everyuthing effects everything else.

Absolutely - the 1.8T engine is known for sludging issues. If they diagnosed oil sludge then your engine is covered no matter the mileage. The oil sludge builds up in the 1.8T no matter how well cared for it is, and the sludge can block the oil pickup screen on the oil pump (it's an extremely fine mesh), causing oil starvation and taking out the engine in the process.

Go to www.audiforums.com and do a search there for "oil sludge" and the information will come up. You can learn all about it there. But if your engine has the sludging, and you have receipts proving the oil was changed at the proper intervals, you will get a new engine free of charge - one of the members there is an Audi technician and I remember him posting that he'd changed out a 180k mile engine under warranty due to sludge.

It is a well Known problem within the 2.7 L family ...
Here is the deal Go to the dealer get a Mopar oil sending unit.
once under the vehicle look to behind oil pan about center ways and take pigtail (wire) off sensor then remove unit .
once removed if alot of sludge is there clean area very good then install new unit and inspect wire if it connection even looks bad cut wire and add new wire (MAKE SURE TO USE HEAT SHRINK TAPE OR LIQIUD ELECTRICAL TAPE TO SEAL WIRE COMPLETELY. >>>>NOT JUST ELECTRIC TAPE<<<<)
Ok now thats done plug wire back into unit .
Note: 2.7 L engines also have sludge problems and need to have engine flush and oil pan dropped clean oil pump screen and pan then start useing synthetic oil you should be able to go about 10,000 miles useing synthetic and you will have to only change filter 2 or 3 times . this should solve issue and help extend life of motor. SB