Unusual engine sounds

[lamb125]

Just checked the receipt for the last service I had done (early Oct 2010) and engine oil used was semi 15/40, I bought 1litre of Wlikos mineral 15/40 for top ups, but have since topped up with halfords semi 15/40 so in effect the engine, at worst, contains 80% semi and 20% mineral; I suspect that the ratio of semi to mineral is actually higher than that.

[jpennington]

IMHO - don't panic.

Semi-synthetic is a mixture of mineral and synthetic oils. That's what 'semi' means. The odd top-up with one or the other is not likely to cause a problem. Now if you are old enough to remember Castrol R vegetable oil - mixing that with mineral oil produced something like jelly. I did smell nice when it was burnt though.

FWIW this post describes my experience of synthetic and other oils, over 25 years in my bus.
viewtopic.php?f=37&t=79169#p7574811.
I very occasionally get tappet rattle when starting if it's due for an oil change and been stood for more than a week. Many years ago (around 1990) I had one tappet that took half an hour to stop ticking, but that was after 4 days parked in the open in February halfway up an Alp.

In my opinion it all depends on the amount of wear in the engine. Since yours seems to be using rather a lot, I guess cheap 20/50 changed frequently is your best bet.

good luck

jp

[lamb125]

I'm only a few miles from you...in Fareham. Would be nice to bump into you sometime, not literally of course!

[jamiemumt]

Ok lads and lassies, I have a 1986 petrol water cooled T25 high top. Engine has done 84.000 miles and I have a noise like a tappet sound from the offside of the engine. I have been reading some of the talk on engine flushes in this forum, and I am not sure if I should go for a flush or not. The noise did go away but has returned, but the van has been wintered, so not used since September. I am getting it ready for its dredded MOT, so what is the views on doing a flush to get rid of the noise, and will it help the emmission output. Also, if I should flush, what product do you suggest?

Cheers,
Jim.

[kevtherev]

You won't get rid of the noise unless you a) use it regularly or b) replace the tappet.

old hydro tappets will always be noisy after a period of inactivity.
Thicker oils help like 20/50 mineral

[T25Convert]

Hi,

You say you are topping up every 300 miles. I had the same issue when using semi-synthetic. Since going back to mineral it is amazing how much less oil it uses - apparently somtheing to do with the oil seals swelling slightly in mineral oil (although thats off the back of the oil can, so it might be marketing rubbish!)

Might be worth a punt though....

Cheers,

Alex

[lamb125]

Hi, yes I reckon it's roughly 300miles between top ups. I'm convinced now that mineral is the way to go. Well I'll see how it goes and report back

[lamb125]

Renewed my oil and filter today. Drained out the old semi having covered just over 3000 miles using it. Refilled with 15W/40 mineral, sounded as a sweet as on tick over. Will monitor for any extraordinary oil usage and get back.