Forum

[PeteF]

Many mechanics will tell you that modern engines and oils don't need flushing oil and I sort of accepted that.
I just changed mechanics for the car and van however (I don't like doing cars) and surprise, surprise, he strongly recommends it.,
Looks like they will be flushed from now on. It's also got me thinking about it for the bikes.

[Dennis C]

I have a Toyota car, the oil is still clean looking when changed, I have a Triumph Sprint ST 955, just changed the oil at the advised 6000 miles it looked as good as new, I have three old British bikes, Triumph, BSA, Royal Enfield, every one has very black oil in a few short miles, all my old Brit bikes over more years than I care to remember have had black oil. All modern multigrade oil is a "detergent oil" and cleans as it goes that is why all by bikes are fitted with oil filters to catch the crap which the oil keeps in circulation and no longer stays in the sludge traps. flushing oil?, your choice, personally I don't think it does any good like it used to with old non detergent oils, but even back when oil was pretty poor and non detergent you risked the flushing oil pulling all the crap out of the crankshaft sludge trap and dropping it straight through the big end/s.

A real can of worms no?.

[papasmurf]

Given the past threads on here about how much oil is left in an Enfield engine at oil changes, (around .7 of a litre,) personally I would not dare use flushing oil in an Enfield.

[jefrs]

2cvandy - my Volvo clocked up 335,000 miles before being written off by a truck whilst it was parked. The engine ran sweet as a nut and the oil came out looking like new because it had regular annual oil changes of full synth. The oil in my C5 looks like new having done a mere 750 miles. If the oil changes colour its detergents are picking up debris and carbon, diesels are notorious for this. Despite not looking discoloured the oil will gradually lose its lubrication properties as the engine mills it until it is water thin. Once the oil is used up then it is time to change irrespective of what the book says.

[jefrs]

Papasmurf - the purpose of flushing is to fetch out the sludge and metal crap the regular oil leaves behind, hence repeating the flush two or three times. If you're getting 700cc left in the motor then it might be beneficial to flush with regular oil to remove the thin flushing oil (it also has extra detergents). The C5 holds 2.75 litres. Some cars have to be tipped, some don't have a drain plug and the sump has to be dropped of, or sucked out of the dipstick tube by a pump; you can see why I gave up servicing modern cars.

If the regular oil comes out clean without grit then it doesn't need a flush.

I only suggested reducing the service interval for this motor which has developed metal filings, mainly so the oil can be inspected.

In theory one can drain the oil for inspection, sieve it and put it back in. I think that's a bit risky and would use new oil.

[papasmurf]

Jefrs, I suspect the only way to get all the oil of an Enfield engine is to take the engine to bits and rebuild it.

[jefrs]

Papasmurf - the first one I had emptied its oil all by its self. Usually 1/4-pint squirted onto my boot whilst pulling it onto its stand.

[PeteF]

Yes, modern petrol car engines don't seem to mucky up the oil like they used to.
This is not true about diesels however. The oil looks pretty mucky after a couple of thousand miles. I suppose they have more blow-by because of the higher compression ratio.
Just because oil is looking clean when it's changed is not a reason to leave it in though. I've always had car oil changed at 10,000 miles regardless of what the book says, and at least annually regardless of mileage.

[2cvandy]

Hi jefrs, my C5 has covered just over 170,000 miles so far, but I've never drained clean oil out of it. Mind you, my C5 is a Citroen 2.0 litre diesel ! Joking aside, I spent over 30 years running a small fleet of taxis and mini-buses, and 3 - 400 k miles was by no means unusual. Always serviced according to the manufacturers recommendations, never used a flushing oil, never drained clean oil out of any of them, and never wore out an engine, it was always the bodies / interiors that wore out first. My point was simply that klutz shouldn't be worrying too much about all this stuff. He'll read on t'internet of people who change the oil every 1,000 miles and have bikes that run superbly, but who's to say they wouldn't run just as well with less attention? If the manufacturers spend time establishing a service routine for their vehicle, I see no reason to assume I know better. My 1987 Transalp has 72,000 on the clock so far with nothing but what Mr Honda recommends, and I think she'll soldier on for a while yet.

[PeteF]

2cvandy.
Interesting observations from your fleet experiences BUT
Those vehicles would have an almost ideal life, running all day everyday just about. When I was at work I never (we almost never) had a problem with the 10 cars I got through but I did anything up to 250 miles a day. Short journeys were almost non existent. We used to change them at 120k and I can never remember ever having an exhaust system or battery replaced. These were workhorses, usually overloaded and thrashed.
Tyres I did get through