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MG MGB GT V8 Factory Originals Technical - Flush engine at oil change.


I'd like to solicit the group's opinion about using an engine flush at the oil change.

I've just added the stuff and drained the oil. It seemed like a good idea, with the Rover having a reputation for slugde build-up.

Now I'm not so happy about the idea of there being a load of 'treated' oil in the oil cooler and associated pipe work and whatever is left in the sump.

I'm contemplating taking the sump off and cleaning it out and attempting to drain the oil cooler. (I want to re-seal the sump anyway.)

What is in the engine flush? is it just a light fraction of oil - it smelled like diesel - that will evaporate off, or is it something like detergent that will break the new oil down.

Am I being paranoid?


Nick Wilson

Might wanna just yank the oil cooler. I did; no regrets.

I wondered about that too, once I started to use flushes. I think it 'boils off' quite rapidly as I have noticed a slight level drop a few miles after refilling that I hadn't noticed before I started flushing. Don't know what the capacity of oil cooler and pipes is, but I reckon any remaining flush is pretty 'diluted' by the other eight (or nearly so) pints.

Paul Hunt

Thanks Paul,

That's the sort of answer I wanted!
Nick Wilson

If you care enough to flush at oil changes, surely you care enough to do it 'properly' ;-)
- just disconnect an oil cooler pipe and pump or syphon the old oil and flush mix out. If the car is jacked up at the 'right' angle then the sump should be clean inside after flushing and draining.
David Smith

I asked the same question about 25 years ago and was told that flushing oil is for post surgery only - not recommended for regular use - the advice which has consistently kept my 1800 and 3500 engines clean came when they first introduced multigrades; buy simple and cheap oils with a good detergent rating and change every 3000.

You may have to modify this if you have a more modern version of the V8 but change frequently.

forget the oil cooler - pressure has already recirculated the remnants of the flush - the bottom of the sump will tell you something about the condition of the engine but again only needs to come off after work on the engine.


Thanks for your input Roger.

Do you have a specific recommendation as to brand and variety of oil?

I use plain old Castrol GTX in my Wife's Golf and in my motorcycle. They have 140k and 65k, respectively. Both are changed every 3k. The Golf is not showing any signs (touch wood) of wear, yet.

I bought Castrol Magnatech (not sure about the spelling) after ages of dithering. I couldn't bring myself to buy the cheapest oil for my lovely V8 - but at the same time I'll never know if it makes any difference.

My descision to use a flushing agent was based on the 3.5's reputation for sludge build-up. Perhaps this is only a problem if oil change intervals are extended??

Nick Wilson

Clive Wheatley strongly recommends the use of a flush (Forte) to keep the hydraulic tappets clear. I use 'ordinary' GTX (there are at least three different types now, it seems) in both my MGBs. Funny how when it first came out I sneered at it as a boy-racers oil, now it is a classic.

Paul Hunt

Jesus! Paul,

I thought Castrol GTX had been available forever. ;-)

Nick Wilson

I have never flush an engine and always have had clean long lasting engines even in racing conditions. Some flush liquids actually have chemicals that destroy the bearing surfaces.
Roger has the best advice.

I change the oil on all my cars every 3K miles but I also use a quart of ATF (Automatic Transmission Fluid) for about 100 to 200 miles prior to changing the oil and filter.
ATF is the best lubricant/cleaner there is. The problem with ATF is that it foams when use on an engine, otherwise it could be used as an engine oil.
ATF is use to clean aircraft parts etc. If you have use flush on your engine, next time try a quart of ATF before you change oil next time, and see the black stuff that will come out when you drain the oil. If you know of anyone who has noisy hydraulic lifters, tell them to put a quart of ATF and the lifters will be quiet again in matter of a few miles.

ATF Dextron II has more cleaning agents than others.

It is also a great penetrating oil and even better when mixed with some Kerosene. 50/50 It's also a great air tool lubricant.

ATF can also be used on solvent cleaners to prevent dryness of the hands.

Now! Change the colour, put it on small pints, name it, and sell it.

Don't forget to share the profits.


Bill Guzman

Nick, it has, believe me, it has ...
Paul Hunt

modern oils clean anything, even your engine. My B sprung a leak and dumped over a quart of oil on the concrete garage floor. I spread a layer of clay absorbent to soak up the oil. The absorbent did just that. The oil carried with it the dirt from the garage floor. The area that was sullied with oil is now noticeably cleaner than the surrounding area. I recently pulled down the bottom end of my wife's 89 taurus SHO engine which had the oil changed about once a year. After 78,000 miles the engine looked brand new. Not a sign of sludge or carbon deposit anywhere. If someone showed you the insides and told you it was a new engine you would not be able to prove him wrong.
Barry Parkinson

There are a range of little Companies which make oil for the big boys - I am away from my garage at the moment otherwise I would give the name of the one I use which also makes Duckhams - but over the years I have used comma and halfords own brand.

Useful tip about ATF - particularly if your engine has a murky past. But ATF is quite expensive here and I might not keep up your regime once I felt that all was well.

Best wishes R

This thread was discussed between 27/11/2000 and 30/11/2000

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