I have just purchased a 99 2500 Suburban with 100k miles. Upon closer inspection the vehicle has not been maintained as claimed. I went to check the oil and it was a dark balck and gray color. Immediately I changed the oil using 15W-40 and installed a K&N oil filter hoping to clean up what crap was hanging around in the engine. After the change I restarted it, let it idle, then drove it around the block. Nothing major. I checked the oil 5 minutes later and it was already that black and gray color again. Any suggestions on what I need to do to clean it up? Does the color of the oil suggest anything abnormal going on? Thanks.

The oil should be black, but not gray. It's getting black again about immediately after you change it, that's normal.

I've been running 10W40 and later 5W40, and I'd recommend a good 5W40. Both types are worn out after about 8kkm.

If you switch from mineral oil to synthetic oil, the synthetic oil will loosen dirt from inside the engine, so change it early for the first 3--4 times after the switch. Then, it takes somewhat longer before new oil becomes that black.

Use oil filters from Delco or Purolator.

Hello Budroe--Olee is correct on the color, it's ok when black--the color really has nothing to do with the condition of the oil. The only thing that can absolutely tell the condition of the oil is oil analysis!! If it were my motor, I would first flush the engine with Amsoil engine flush!! It's cheep--it costs about $5.00. by flushing the motor you will clean it out-remove all the crap thats in there due to lack of oil changes, it sounds like!! I would then replace the oil and filter with Amsoil 15-40 diesel and marine and an Amsoil oil filter SDF24!! Run it about 3000 miles--take a sample of oil and have it analylized through oil analyzers. Good luck to you!!

Greg Carter Vermont

Where can you get the Amsol motor flush, oil and filter. and how do you do it. I talked to a guy a little while ago and he suggested putting a quart of tranny fluid in and that should clean it up. He maybe as carazy as an outhouse rat but Id thought Id mention it. I guess im used to changing oil in gas motors with the oil staying clean for 3k miles. Where do I go for an oil analysis? Sorry for all the questions but Im just trying to learn.

Budroe---Please dont use that home remedy that guy suggested--What you need to do, is find an Amsoil dealer in your area--it's possible to find Amsoil products in a parts store-but i dought it! They are usually sold through an independent dealer-check the yellow pages. If you cant find it around you, there is a supporting sponcer on here who can help you!! His name is Greg landuyt --Lubication Specialist LLC--his phone # is 1-888-306-4255--tell him Greg Carter sent you--tell him your problem and what I suggested you do!! He is an Amsoil dealer and will have everything you need at a good price!! This is the best thing you could do for that motor--at least you will clean it up and if something is wrong the oil analyis will help pin point the problem!! Let me know how you come out!!

Greg Carter Vermont

www.lubespecalist.com sells sample kits and bypass filtration kits Kennedy still may be selling bypass kits as well haven't checked his site in a while, but rather than the amzoil kit alone with high $$$ amzoil filters, get the kennedy adapter that allows running Baldwin filters on the amzoil bypass kit. Chevron DELO or Shell Rotella 15W-40 is standard oil recommended by many, synthetics are fine but why pay extra if quality dino oil meets-exceeds factory specs, with bypass 7500 mi interval is possible, no problem, 3000-3500 mi stock filtration is a good interval. I've just sent in a 10,000 mi extended interval sample to see how effective bypass filtration is, I'll probably be settling on 7500 with bypass on mine for my change interval. but for $$$ buy in bulk 15W-40 $33 for 5 gal Rotella is good bang for buck. More info on oil in FAQS

budroe,
you have PM

I was wondering if you're engine is using any antifreeze? If your oil is turning gray in color it usually indicates water in the oil.