Oil blackening quickly

[tomti]

Hello all,

I've had our Minor serviced in preparation for a French honeymoon, and many things that were once bad are now much better (steering, braking etc.). I had it all done by Richard Plant near Oxford and he was immensely helpful.

However, something is bothering me. The oil was changed and the filter replaced, as one would expect. During the replacement of the filter, it was found that the previous person had put it back together incorrectly and therefore the engine had been running on unfiltered/poorly filtered oil for an unspecified amount of time. I'm now very glad I decided to get it serviced as soon after buying it as I did - damage was doubtless done but hopefully not too much.

The thing that seems worrying to my untutored eye is that, on checking the oil levels and topping up as I have been doing every trip or so since we got the car (there's been a fair bit of motorway involved in the last couple of months by necessity), the new oil as seen on the dipstick is already very dark indeed - black, in fact. There isn't any sludge on the rockers, though.

I am no expert by any stretch, but I'd have expected the oil to stay more transparent for at least a bit after being changed. We've done perhaps 500 miles since the service at most.

Is this normal or should I be concerned? Should I change the oil again before doing 1000 miles across France?

Any advice gratefully received.

-Tom

[bmcecosse]

As you suspect - it's cleaning out all the rubbish that has accumulated over the years - especially with no filter on the car.... Yes - I suggest you change the oil and filter again. Ideally - sump off and scrape out the worst, but I guess you may not have time for that. Wilko 20W50 is fine - no need for anything fancy, but don't expect it to last 'for ever' - change it frequently!

[tomti]

Thank you - definitely no time to take the sump off right now but I will do my damnedest to fit in an oil and filter change before we leave on Friday. If time gets tight I might have to take the bits with me and do it on the other side of the Channel before we get too far!

-Tom

[dalebrignall]

just give it a oil and filter change i used to find that after 700 miles the iol had gone black it shows its doing its job .thease are old engines and the oil wont stay clean for long i tend to change my oil every 2000 miles .

[lambrettalad]

a spin on kit is worth while,makes changing the oil much easier,nothing to put in incorrectly,

I drive mine between one and two k per year,so I change oil every year at MOT time,using wilco as a flushing oil ,as its good and cheap,the refilling using either wilco again and any number of mineral 20/50 oils ,this year i'm treating "froggie" to Fuchs Classic

Have a great honeymoon,you will be able to tell your grandchildren about your romantic honeymoon in France with you moggie oil filter and tools

[JOWETTJAVELIN]

Perfectly normal for the oil to start darkening after a few hundred miles. Why I don't know - probably to do with decades of use and engineering tolerances being a lot larger than nowadays.

[MarkyB]

There could easily be half an inch of sludge in the sump mostly made up of carbon.
Modern oils contain detergents which will clean it and hold it in suspension, a lot more so in oil designed for diesel engines.
Scraping the sump out will improve matters a lot visually but that isn't really the way to judge if the oil needs changing.
Americans get their oil analysed, I rely more on the look, smell, and feel between the fingers.

[David53]

My engine was fully stripped, acid bath cleaned and rebuilt with all new parts when I did the resto a few years back. I have since covered about 5,000 miles. The sump was dropped about 1500 miles ago and scrubbed clean. My oil gets dark after about 500 miles, and totally black by 1000 miles. I think it's normal though why it doesn't happen on modern cars is beyond me.

[bmcecosse]

Simply because they are built to much tighter tolerances with negligible oil consumption, and no contact between the combustion products and the oil.

[David53]

I would suggest a complete oil change and grease of all nipples before you take the car on any long journey. Costs very little and worth it for peace of mind.

[JOWETTJAVELIN]

Agree David. Fresh oil is cheaper than an engine rebuild.

[C6Dave]

I would change the oil and filter annually and if it's going to be in the garage for a lot of the winter, change it before you put the car away so it's not sitting full of contaminates.

I also change the oil and filter on my modern diesel annually, as oil if far cheaper than a blown turbo...............

[MarkyB]

I suspect that there is more to modern cars longevity and lack of oil consumption than just better tolerances although they must play a part.
Presumably design and materials have changed along with lubricants and fuel but I've not had any reason to rebuild anything even slightly modern so cannot really say.
Has anyone here opened up a reasonably modern engine to know what the differences are?

[JOWETTJAVELIN]

I wouldn't dare, Mark! Talk about jam-packed engine bays. However I once saw an Audi block at my local garage and there seemed nothing about it we wouldn't recognise. I suspect a lot of modern engine technology is more fuel delivery, combustion and top-end related, rather than the bottom end.

How they work on such thin oil and don't generally use much is a wonder though.

[bmcecosse]

Tight tolerances.better material for the rings/coating on the bores/better bearing material (Al/Sn) and close tolerances on the crank dimensions - and better oil pump and filters! Also no doubt the oil is better - and much more expensive !

[rayofleamington]

Presumably design and materials have changed along with lubricants and fuel but I've not had any reason to rebuild anything even slightly modern so cannot really say.
Has anyone here opened up a reasonably modern engine to know what the differences are

Cylinder bore tolerances, piston ring design, piston heat distortion (lack of), piston design, valve stem tolerances & heat distortion (lack of) and valve guide tolerances and sealing method... all of which reduce oil consumption and reduce carbon entering the oily sie of an engine.

[MarkyB]

piston heat distortion (lack of)

So if we could find modern pistons and rings then re bored to a tighter tolerance it should take us part of the way there.
Better ring sealing would mean less crankcase pressure and lead to less leaks from elsewhere too.
< Puts thinking cap on> Where is there a database of piston sizes?

[bmcecosse]

Yes - but the block expansion/contraction with heating/cooling will come into it too. And valve stems/guides/seals... and improved air and oil filtration!

[JOWETTJAVELIN]

As the A-series is a tough engine anyway (803 excepted!) we should all be OK. 100,000+ miles is common before major attention is needed. It all depends on how it was looked after in the past, which is the worry.