Do you think 1 year and 6500km is too long to wait before oil changes? I did put in 2 extra Liters in that time. The oil was very dark and dirty when I drained it.

Techincally, you could take an oil sample and get it tested. Personally, I don't like dirty oil in gas engines unless they have a ton of miles on them. Can't get away from it with alot of miles. Although, my wife has an 09 G6 and I am amazed at how dirty the oil looks after 3000 miles.

I agree i really hate the oil comming out that dirty I only have 72K miles on it.

IS there any engine flush that you can use that are safe?

Modern oils, synthetics and dino are HD lubricants. The HD (not heavy duty) stands for high detergent. The oil is designed to help reduce sludge build-up by holding dirt particles in suspension so they don't settle in the oil pan and on other engine surfaces. The dirt and soot drains out of the engine during normal oil changes. Of course, everything has its limits. If the oil is overloaded with dirt and soot for a variety of reasons such as worn engine conditions , improper fuel mixtures ( bad injectors), contaminated oil or just plain over-extended oil change intervals, sludge will still form. Oil is supposed to look dirty but only a chemical analysis will show if it is too dirty. I've taken a lot of grief over using expensive synthetics and changing them at less than maximum intervals but in over 50 years of driving and servicing internal combustion engines, I have never experienced an oil related failure.(unless you count the time the overhead oiler on my 61 Falcon, kit supplied copper tubing, work hardened and broke off in the middle of a trip from Muncie, Ind. to Chicago and pumped all the oil out of the engine. Luckily I noticed the oil spraying on the windshield and shut the engine off before any damage was done. I walked 3 miles to a service station to buy 4 qts. of oil and drove the rest of the way with a vise grips clamped on the tubing from the oil pressure sending unit tee fitting. Never use copper tubing for oil, fuel or brake line replacement!)

I don't put many miles on my truck. I typically go 3 years and 5K miles before I change mine. Have never had a problem since 1984 with any of my trucks.

DEWFPO

I have put over 15,000 kms on Mobile 1 full syn in my 6.0. It was as clean as the day it went in though, so I didn't worry about it. That also was only about 4-5 months of service.

If in doubt, change it, but save some and get it tested, and you will have your answer for next time.