Oil viscosity

[Tufftrax]

Just changed my 1981 350 Sport's engine oil in preparation for winter lay-up and used Castrol GTX as recommended in Morini handbook.

However, I did not appreciate that Castrol make a 10W/40 and 15W/40 grade GTX and used 15W/40 as that was all that was available from my local Halfords.

My bike is not going to be used in cold weather so will the 15W/40 be OK or should I have used 10W/40 or does it really make no difference?

Not being particularly mechanically minded I thought I'd ask fellow owners for their words of wisdom!

Thanks in advance,

Keith

[Daddy Dom]

My extremely mechanical reply would be "what's 5w between friends?" And if winter lay-up means you're not using it, you should be fine.

Someone who really knows will be along in a Bologna minute, I'm sure.

Cheers,
DD

[EVguru]

The people who wrote the handbook were not fortune tellers. Don't take what's in the book as gospel. Many people have been injured or killed becuase they insisted on using the tyre pressures in old manuals, rather than what the tyre manufacturer recommended for the tyres made NOW.

The original oil specified by Morini was Castrol 20w50, pretty much the best oil available at the time.

The late oil specified by Morini was Sint AGIP 2000, which is semi synthetic 10w40 and considerably better than old 20w50 in terms of lubricity and engine protection.

I used Halfords own brand semi synthetic 10w40 because it's quite cheap (particularly when they've got a deal on) and almost certainly far better than a 20w50 of 30 odd years ago.

The semi/full synthetics tend to cling, rather than drain down and protect the valve gear on Morinis that are only used occasionally.

[72degrees]

I used Halfords own brand semi synthetic 10w40 because it's quite cheap (particularly when they've got a deal on) and almost certainly far better than a 20w50 of 30 odd years ago.

The semi/full synthetics tend to cling, rather than drain down and protect the valve gear on Morinis that are only used occasionally.

+1

[3potjohn]

What's all this about a winter layup-it was about 30 celcius in Gravesend today.

[HoveActually]

As a very new owner its very likely I don't know what I'm talking about but here's my 5 penny's worth anyway.
Not knowing what oil was in the bike (or when it was last changed) when I bought it, I put in some Rock Oil Semi synthetic 10w40. Cheap from WEMoto especially since I live on their doorstep.
Gear changing which had been OK now became horrible, notchy, false neutrals, etc.
I only did 100m with the 10w40 oil and quickly changed to Millers Classic Mini 20w50.
This is the stuff! http://www.millersoils.net/1_Millers_frame_CLASSIC.htm
Absolute magic - now done 200m and gear changing is like a modern Suzuki which means near perfect. I know I should wash my mouth out but I'm as pleased as punch over what may seem bloody obvious to experienced classic bike owners.

[72degrees]

Presumably that was once the motor was good and hot, because I don't see how 'thinner' oil at low temperature should affect gear changing. When I had the Voxan I used Castrol RS 10w 60 full synthetic as they are prone to very hot running and premature cam wear. You can't get the recommended Motul 15w 50 (Voxan) oil in the UK. The dealer in Limoges who supplied the bike suggested it. When I was asking Castrol about it they *claimed* the classic mini owners swore by it - so you pays your money and takes your choice.

One question mark over 'car type' synthetics in engines not designed for them is the clutch (no problem on the dry clutch Morinis) and starter sprag clutches (again not an issue). All I can say is that the tuned 375 lump in my 2C (which I've owned for 30 years) seems just fine on 10w 40. Though if I thought it was going to get a really sustained thrashing in hot weather I might go for that 50 upper range to be on the safe side, but I''d still go for synthetic over mineral.

[Ralph]

I have always used 10/40 semi synth in my early Strada
no problems at all the gear box is as good or better than
any modern bike I have ridden and I cant remember the
last time I had to adjust the tappets.

[MickeyMoto]

Castrol Magnatec 10W/40 Semi Synthetic in Halford -

4 litres £17.99 instead of £28.99