If the car is well maintained, the oil flush is probably worthless.

I just worked on a 91 740. The car had an extensive maintenance history with one shop, including a very thorough going-over at 171K when it was sold to the last owner. A friend of mine bought it and asked me to look it over. I replaced a slightly leaking valve cover gasket. Under that cover, I swear that engine looked brand new. Everything was golden in color and shiny. There was no sludge, no chunks of anything hidden in the corners, it was just nice and clean. No evidence that anything was needed other than another oil change when the time came.

This car had 301K on it. That's miles, not kilometers.

Do the regular maintenance, clean the flame trap, clean the throttle body, replace the seals and gaskets that need it, and give the snake oil to your friends who drive Buicks. They won't really notice whether the engine fails at 135K or 140K.

--
::: Rob Bareiss, New London CT ::: 92 244 M47 211K ::: 90 745GL M47 273K ::: 88 245DL AW70 190K ::: 84 242DL Project ::: 70 VW Bus ::: 70 VW Pickup Project ::: 71 VW Notchback :::

You'll risk washing away any non-intrusive crud that is keeping old seals from leaking. Do you have any desire to open a leak in a rear crank seal that is leak free?

Greg Mustang
www.volvoclassic.bravehost.com

My std. procedure with a 'new' used car is to immediately change the oil and filter, using 5W30, and drive it for about 100mi or so and drain it hot. Change the oil and filter and resume normal change intervals with your usual choice of oil. I try to only buy cars with a maintenance record and/or which show evidence of good maintenance, so there's no need for chemical flushes. If your engine looks dirty just shorten the interval between oil changes a few times.

Here's a GM TSB from Nov. 2003:

"... GM does NOT endorse or
recommend crankcase flushing for any of its gasoline engines. Analysis of
some of the materials used for crankcase flushing procedures indicates
incompatibility with GM engine components and the potential for damage to some
engine seals and bearings. Damage to engine components resulting from
crankcase flushing procedures is not covered under the terms of the New
Vehicle Warranty."
--
Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD and 89 745 (LT-1 V8); hobbycar 77 MGB, and a few old motorcycles)

Personally I wouldn't do it. Who knows what you might break loose?

If you want to do some light cleaning then perhaps try a heavy duty/fleet motor oil in the 10W-30 or 5W-40 grades. Chevron Delo is available (but hard to find) in 10W-30. Shella Rotella T Synthetic is available in 5W-40 at a reasonable (for synthetic) price at most WalMarts.

I'm no fan of putting solvents in an engine and then running it, which is what most motor flush products are.

Do 1,000 mile interval oil changes with one of the above oils 2 or 3 times if you want to do a general light cleaning.

John

I've heard stories of those fast flush's dislodging large chunks of sludge and clogging up the oil pump or the oil passages.
Although I've never had any experience with them, thats what I've heard....Folklore? Perhaps.
Here's how I flush an engine:
Get 3 quarts of any 10w30 oil
Get 2 oil filters
Get 1 quart of Marvels Mystery oil
Get 1 bottle of CD-2 engine flush

Drain all old oil and remove old filter.
Pour in Marvels Mystery Oil and CD-2 detergent
Top off with 2 3/4 quarts of 10w30
Install new oil filter.

Drive for 1500 miles then replace just the filter
Top off oil again with rest of 10w30. Drive another 1500 and change oil again.

At this point take a look into your oil cap hole. If things still look cruddy, add a half quart of Marvels Mystery oil and top off with 10w30 and new filter.

Monitor the cleanliness of the engine. Marvels works wonders! CD-2 helps it out alot too. The CD-2 is heavy in detergents as well. You want to change the filter half way through because I can guarantee its getting plugged with crud being removed from the internals of the engine. I've been doing this to every car I buy for years now with great results. I did it to my wifes when we bought it last year. The internals of her engine head had a "coffee" colored film all over it. I used this method and after just 3000 miles the internals are a nice silver aluminum color again.
I am currently doing this on my 240 I have right now as well. I have only driven 200 miles using this, but I am starting to see results when I peer through the oil fill cap.

The oil viscosity is thinner for awhile when doing this, but thats ok. The oil circulates much better to get into every nook while doing this process.

Just my method. Others may have other ways as well. But I stand by this method.

If the flame trap needs replacing, you should consider cleaning out thebreather box, underneath. I just did mine and it was full of crud. It wold certainly be hard with the manifold in the way. Here is a useful link http://www.brickboard.com/FAQ/700-900/EngineSealsBeltsVent.htm#Crankcase_Ventilation_A_Treatise