Engine oil flush

[Healeyalt]

Next week I'm picking up a 1976 with the orginal motor which supposedly runs pretty well, Its got around 80K miles on it (hopefully not 180K). Anyway, the first thing I plan on doing is checking the oil and changing it and the oil filter. I'm thinking of pulling the valve cover and oil pan first to clean out any "gunk".

Have or would any of you guys use somehing like Amsoil engine oil flush in these motors?

Or would this just open up a lot of leaks and other problems?

I'm sure down the road I'm looking at a rebuild, but I don't currently have the time or money so I'm thinking of changing all the fluids for now (antifreeze, brake fluid, differential fluid, etc) and cleaning things up as best as I can.

I appreciate any advice or experiience.

Thanks

Gary

[pwd]

A little trick an old timer taught me ages ago was to simply replace half your oil with kerosene and run it awhile. It will accomplish the same task for a lot less money. Most of these "oil flush" chemicals are "petroleum distillates," which turn out to smell a lot like kerosene.

[beermanpete]

I don't like the idea of those type of products. It seems like the solvents in them would degrade the protection offered by the oil.

Modern oils have a lot of detergent additives in them. Fresh oil will "wash" the engine and pick up most of the deposits that are easily dissovled. Change the oil after a few hundred miles if it gets dirty quickly.

[d240zx2]

"Back in the day (the '50s)" I used diesel fuel for the same purpose. Ran it for about 10 minutes to get things warmed up, dumped the oil, added the diesel fuel, ran it for 5 minutes at idle, dumped it. Fresh oil for 15 minutes and dumped it. New filter and oil and off we go. No issues with engines of that era. I wouldn't recommend it with today's engines and oils, though and beermanpete has a better solution than what I did 50 years ago.

[Zedyone_kenobi]

wow, you put diesel fuel in the crankcase! I wonder who was brave enough to try this first!!

[FastWoman]

I used to use Gunk motor flush periodically on my '75 Z from long ago. I did this from 80k to 120k miles, when I sold the car.

I gave my 168k 1978 Z one flush with Gunk, and it worked fine. The only problem (and the major difference between the two cars) is that my old '75 had occasional varnish (nothing unusual), while my more recently owned '78 looked like a caked up BBQ grill under the valve cover. I honestly didn't know it was that bad, or I wouldn't have so casually done the flush. When you liberate that much crap in the engine, you can block up oil passages and filter screens.

Fortunately I had no problems. Also there were no oil leakage/burning problems with any engine I've ever flushed. I've done this many times -- 2 280Zs, a BMW Z3, a Saturn SL2, a '66 Mustang, an '87 Ford Crown Vic, and a '94 Ford Taurus.

I've heard of alternative flushes, such as 1 qt of ATF, 1 qt of kerosine, and a couple of qts of diesel (never heard of a full crank case of the stuff). I've heard of no issues with those. The Gunk motor flush has high volatiles that cut the varnish pretty aggressively, unlike these other methods, but they all work.

For my BBQ grill engine, I've been running a diesel formulation of motor oil -- Chevron Delo, which is very high in detergent and also high in zinc. It's actually a very good/appropriate formulation for our Z engines. The Delo has slowly been cleaning up the remaining crap from my engine, which now looks fairly clean. I've also used an excellent detergent additive called Rislone. However, I think the Delo works better.

Edited November 3, 2011 by FastWoman

[Oiluj]

I've used kerosene in the crankcase to clean things up with good results.

My protocol was:

Warm-up engine. Remove 1 qt of oil & add 1 qt of kerosene. Idle for 15 minutes routine in the past on previous vehicles. Immediately change oil and filter, run engine at idle 10 minutes. Change oil & filter again.

Did that twice in 1 week on my previous Z's L-24 and it seemed to do a good job of cleaning-out the accumulated years of crud & gunk. Oil stayed lookng cleaner, longer than it had before. (of course, if your rings or valve seals are worn, oil will still get dirty pretty quick).

No evidence of ill effect on bearing surfaces found in tear-down of engine, (years later).

YMMV

[cygnusx1]

I recommend against doing anything. Just run modern oil which has excellent detergent properties, and the engine will self clean. Go ahead, next time your hands are dirty, use some fresh motor oil to clean them. You will see how well it actually works. Aggressive engine cleaning chemicals/procedures can cause particulate to come loose, and clog passages and/or become lodged in a bearing. 80K miles is almost within the break-in period for these L motors.

[Walter Moore]

The last car that I ever ran motor flush through apparently had not had an oil change in years. It was an old Chevy with a 305 V8 and a mechanical fuel pump. The motor flush carried crud around to so many places that the push rod for the mechanical fuel pump stuck and the car quit running periodically.

I had to "flush" that engine over and over and over to get it cleaned out before it ever ran half way right.

After that I never used it again.

If the engine is that dirty, just rebuild it. If you don't want to go that far, just put good oil in it and drive the thing.

[olzed]

Just change the oil and drive it --

I bought my 240 12 Years ago. Oil looked like tar. Changed of oil and filters every 1000ml or so and she's good.

[26th-Z]

There's no reason to flush the engine I'm hearing you describe. And I agree. You're just asking for trouble. Just change the oil and filter regularly and perhaps more frequently.

[rotorgoat]

I agree with 26th-Z. I've been running my 78 280 since 1980 with normal (seasonal) oil changes (Valvoline). It was in Alaska for 3 years then Phoenix since then. In Phoenix I'm running Valvoline racing straight 50W in the summer and straight 30W in the winter. I add one half qt of Marvel and one STP to top it off at each change. Never had any lube issues.