So today i got around to another oil change, at about 16400 miles. (07 sport 4x4, 2.4l stick). I was about 4000 miles from the last oil change, longer than i have ever gone. Since the 2d change (1500 miles) I have always used Castrol fully synthetic 5-20w.
This time the oil was dirtier than I have ever seen it - not black, but you could see it easily on the dipstick. The dude at the chain place I patronized said it was so dirty I should flush the engine with his super flusher stuff. I declined the marketing ploy but then I got to wondering - does that stuff work, and should one have to do it on such a new vehicle?
Also was told that I should check the owner's manual for gear box change time, as the oil in my differentials looked "grayish" like "break-in" oil - manual does not mention any need to do that for a while...

I know the guy was trying to make sales, as he is paid to do, but does any of that make sense?

Don't recall what it says in the manual, but differential lube should last a long, long time, a lot more than 16,000. In all my other cars, including my old collector car, you're supposed to check the level of the oil about once a year, which is done by unscrewing a plug, and putting your finger in. It should be full to the level of the plug. If it isn't, top it up with the recommended lube, and find out where it went - out of a worn axle seal, probably. I'll bet the book recommends changing the fluid at 50,000. Also, it's normal for it to discolour with time.

Makes CENTS to the oil change guy.

Follow the schedule in the Owners manual.

Ignore both your Dealer and especially the oil change places that want to rip you off.

You don't need engine flushes or changing of differentials.

The only exceptions to the owners manuals would be if you were towing 2000lb's for thousands of miles.

If the strange color of the differential fluid is caused by water (from running through deep water) then you should change it.

You know what?...next oil change take it to the dealer and let them make the call.
I do know that for older engines, mechanics totally disapprove oil engine flushes as it could potentially dislodge some gunk from around an seal, and then you got yourself an oil leak.

Engine flush?! I've never heard of such a thing. It's not recommended in the maintanance schedule so I wouldn't do it. Heck, it doesn't even make sense to me.

Oil turns black, that means it's doing it's job. If you change it every 3 months or 3000 miles, you should never have to flush the engine. Even if you forget and go twice that long, you should never have to flush and engine.

"grayish" like "break-in" oil

They don't fill these things with "break-in oil" then not tell you to change it after a certain interval. Again, I've never heard of break in oil. Like a previous post mentioned, water mixed with oil can make it frothy or gray and if you suspect you've got water in your oil, you should change it and if you just don't know, I'd bring it to a reputable dealer and have them look at it. It is in their best interest to keep your drivetrain running if you have the lifetime warrentee.

I'd stay away from that service station and start looking around for someone you can trust because he gave you two bits of very questionable advice.

NEVER flush an engine - he's blowing smoke up your a$$!

The oil is darker because your engine is normal. Normal oil will be dark grey at oil change interval. It's nothing more than normal combustion soot scrubbed off the cyclinder walls by the rings. Doesn't hurt a thing, and the detergents in your oil keep it that way.

Ask the jacka$$ how much lube your bearings and valve train are gonna be getting while he and one of his punk coworkers run what is essentially paint stripper through your motor for 15 minutes!

The diff is fine. Gear lube is darker from the start, and they don't require the fine tolerances a motor needs to stay healty.

Here's a trick: glue a strong magnet to the bottom of the transfer case. It'll crab onto anything metallic in the lube. Did this in the Army and it worked great. Doesn't really need it, but it makes you sleep better!

I don't necessarily agree with many of these folks...I have a feeling none of them have had to deal with a motor with sludge...I had an 01 saab 9-3 that I learned alot about engine wear and sludge...After a ton of research on this and talking with many many performance gear heads they all agreed that BG products are awesome...They can be very hard to find and all garages I've found that have them won't sell them to you and say "they're for mechanics"...I wouldn't think after 16k miles you've got sludge but I tell ya what BG makes a product called "quick clean" that is amazing on minor to moderate sludge build up...I used it for the first time in my Saab and was floored as to how much crap came out of there...People can argue that some of that "crap" is good because it clogs leaks...Which, by the way, is an argument for not switching to full syn on high mileage motors...

If I were you I would do an oil change and let it idle for 20 mins and do another one and see what the oil looks like...Filter and oil...I'm sure you're fine but I don't have any idea how prone these motors are to sludge build up...You can never hurt anything by doing 1 to many oil changes...

They make magnetic drain plugs if that's your worry...like 3 bucks...

"Flushing" of various fluids is a complete dealer scam.

Not only are there specific notes in the user manual that such flushing is not necessary, but the situation has gotten so bad that Chrysler/Jeep has gone to the trouble of issuing a specific tsb ( http://www.wkjeeps.com/misc/Patriot/TSB/tsb_2600307.pdf ) which states:

"Chrysler Group vehicle fluid systems do NOT require regular flushing. These systems include: engine oil, transmission oil, axle lube, brake fluid, power steering fluid, and refrigerant. The only exception to this requirement are published in the vehicle maintenance schedules, e.g. engine coolant."

Not only do you have the "if it ain't broke don't fix it" possibility of something being damaged during the needless flushing process which would have been fine otherwise, ther is some possibility depending upon what process and if third party products are used that with this tsb out, of actually voiding your warranty. I agree it's a slim chance, but still Chrysler/Jeep does NOT endorse it.

16,000 miles? No flushing. No way.

Milky oil means water is present. Not that that's what you got, but in any case, milky = wet. Also, as far as break-in oil... my brother bought a new honda civic, and they had some additive in it, (probably helps gunk up the seals), and they said to give it an extra 50% long oil change interval before your very first oil change. Normally the rest of us think of getting rid of the first oil pretty quick to get rid of any shavings etc from building the thing... but that's all hype i guess. thinking of it, I suppose the oil filter would catch that all within the first hour of driving and then you're smooth sailing after...

If you are worried about cleaning the inside of the engine, you don't need to buy "engine flush", which as stated by some one earlier, is a harsh chemical to run through your engine. I've only ever recommended substituting a quart of engine oil for a quart of transmission fluid (on a 5 or more qt engine, use less on a 4qt or less engine). Trans fluid is highly detergent and you can safely drive several hundreds to a thousand miles this way. It works great for cleaning out lifters and getting rid of lifter tapping (due to dirt, not wear). I think the manual transmission has a 25k mile fluid change interval IF you're towing.

If you're changing the oil every 3k miles though, don't even worry about it. The manual states 6k mile interval for normal driving so your one 4k mile change is no biggie.

Go to Bob Is The Oil Guy forum and look at the used and virgin oil analysis. Most SM oils have alot of detergent in them already but it can vary. I would never get an engine flush at any garage or quick lube place, waste of cash and more chance of ****ing up your engine then cleaning it.

No such thing as break in oil in a new car these days--thats all gobbledegook--all oils are reccomended & ready to go off the prouction line..!!