You will find different opinions on using engine flush from every mechanic out there. Some say never use it no matter what. Others put it in at every oil change.
So why the difference in opinion? What are the pros and cons?
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| Valvoline detergent-based engine flush. |
First, what happens to your oil, as it circulates round the engine?
1) As most will already know, the oil is there to maintain a 'safe' gap between metal surfaces so they don't wear each other away. When the engine starts, oil is pumped around all moving parts and keeps everything moving nicely, but it's not an instant transition. The first couple of seconds will be spent trying to build oil pressure and flow — and that's just one of the reasons it's not a good idea to rev a cold engine.
2) Because most oil contains detergents, it's constantly cleaning the internals as it flows, holding the dirt particles in suspension. This gets transferred back to the sump and is filtered before being sent round again. And on it goes... until it can hold no more.
3) The oil is also subjected to pretty severe conditions during engine operation. There's high temperatures in the cylinder head and block/barrels, and part of its job is to move that heat away from the combustion process. Oil coolers help to keep the oil at a constant temperature, but the oil still needs to be able to work in both cold and extremely hot conditions.
4) In a lot of bike engines the oil is also being squeezed to oblivion between gears and clutches too, picking up metal particles as it goes. A magnet in the sump plug is great for holding any steel or iron filings until the next oil change. Clean it every time it's out.
5) In a final act of humiliation, the oil is subjected to combustion gases and unburnt fuel that bypass the piston rings. These mix to form dirty carbon particles which are left around the engine internals, or circulate in the oil. And you're supposed to keep running that same abused oil for thousands of miles.
6) After a while, your oil, or its additives, break down (and that's another story all by itself), and there's more chance of metal-to-metal contact; this obviously equates to engine wear, be it in bearings, cylinder walls, pistons etc.
Yes, your oil is busy every time you start your engine!
What hope is there?
To start with, you can change the oil and filter at the correct intervals, worked out by the manufacturer for the country you live in. Keep on top of that and you'll probably never need to reach for a bottle of flush. That oil will always look nice and clean in your sight glass, and probably look pretty good as it runs out of the sump too.
Every time you remove the oil, you take with it all the dirty particles and tiny pieces of metal that have collected during each engine operation. This is how you look after the engine, keep it clean inside and get years of reliable use.
Lazy owners.
But then we have the situation where the oil hasn't been changed regularly. Old bikes suffer the most. We've all picked up something cheap, checked the basics and found black, dirty oil with loads of shiny, metallic particles floating around in it.
But recently I found the same thing on a 2012 GSXR750. The bike itself was like new, with low k's on the clock. But it didn't look like the oil had ever been changed. Even after an oil and filter, it still wasn't what you'd expect. So we decided to flush it. I was very surprised at the oil contamination. It looked cleanish, but seemed to have a fair few metal particles in it. Since the flush though, it's looked good.
Engine flush.
There's two kinds of flush on the market (unless someone wants to enlighten me). Detergent-based, and solvent-based.
As the names might suggest, the detergent is slightly easier going than the other and will not harm the seals in an engine if left in for longer than specified.
But the solvent version is going to shift more carbon build-up, and is fine on seals if only used for the ten minutes running time specified.
Once added to the oil and engine started, it'll begin to break down the carbon deposits around the engine. They'll circulate with the oil and also begin to wash down into the sump. And this is what everyone gets their knickers in a twist about.
DANGER!
If enough of this debris can fall into the sump, it's entirely possible that it will collect at the oil pump pick-up (a metal gauze), and block it.
Needless to say, if this happens, there will be no oil pressure and major damage will ensue. In scenarios like this, the sump really needs to come off first, and everything cleaned and inspected. This might be something you have to do a couple of times, and also why the old guard say you can't use engine flush — but the engine is pretty much knackered at that stage if you leave it, so why wouldn't you give it a whirl?
More often than not though, you'll find the thicker, dirtier oil will just drain out and bring the rubbish out with it. Even if you have to go and do a few miles first, and then flush again it's preferable to replacing the engine.
It's never going to make a worn engine perform as new, but it might get you a few more years before a major rebuild or replacement.
In case you haven't seen the carnage that goes on inside your engine when you neglect it, the pic below is typical of an engine that has missed a few oil changes. The carbon build-up is horrendous and only the parts that scrape each other are kept clean and visible. For this Captiva, it was all over.
Those of you that are used to working on cars will have seen some pretty bad situations under the rocker cover. A lack of oil changes has ruined many an engine because the build-up prevents the oil getting to where it needs to go. On a side, if you ever look at buying a car, take off the oil filler cap and check inside for deposits on the cap or in the engine. If there's a lot of build-up, it's not been looked after and will probably fail. Colder countries suffer less, but Australia is very harsh on engine internals and oils.
Back to bikes.
If you've seen my post on the sump removal of the GSX, it wasn't pretty. My oil pump wasn't pumping properly and years of using, what looked like, the same oil had taken their toll on what was in the sump — thick gunk.
Half the battle in a situation like this is to remove the sump and clean everything out. The oil pump can then only pick up clean oil and circulate it everywhere, flushing loose deposits as it goes. When I put it back together the sump, and its galleries, were like new, and the oil I refilled it with stayed clean once started. And it wasn't like the rest of the engine was dirty anyway, the top of the cylinder head, camshafts etc. were all nice and clean.
But I wanted to run a flush through it to wash out the engine's oil galleries. I'm using a solvent-based cleaner from Valvoline because I've heard good things from guys who actually use it and have seen how it performs. One of these fellas experimented by spraying it on stripped engine parts and he said the thick, hardened grime which is hard to budge with a scraper, just melts and starts to run down the engine. High praise indeed.
Ten minutes of running the motor and it was off with the exhaust ready to drain the oil. The oil looked clean, but contained a lot of shiny, metal particles. The filter is new so once the chamber was cleaned out, it went back in. New 20/50 semi-synthetic was poured into the GSX and hopefully all is good. It should be 10/40 admittedly, but the temperatures up here are pretty high and this oil contains additives to soften seals and reduce oil burning. I'll see how it goes.
It's hard to see in this picture, but the oil had a lot of glistening particles suspended in it. Hopefully thats not a complete piston floating in there...
Conclusion.
Do you need to flush your engine? If it's serviced as the manufacturer intended, with quality oil, and everything looks good then I'd say you're wasting your time and money.
But if you've missed just one oil change, and you can see black deposits forming inside the engine then yes, it's time to do it.
Engines put up with a myriad of abuse from cold starts, over-revving, overheating etc., and the oil carries a reminder of every single occasion with it.
For me, I'm about to find out if the mid-size GSX has been saved or not (and it's more about that for me than anything else). At least now it has a fighting chance.
More soon...
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