Half price oil at Morrisons UK

[simon duval smith]

Morrisons supermarket petrol stations are having a half price sale of all their Havoline lines this week:

5 litres of fully synthetic 5w - 30 Energy (works really well in the diesels and actually has cut my fuel consumption in petrol engined cars by about 3 per cent)
was £16.99
now £8.49

15 - 40 part synthetic down from ££14.99 to £7.49

Premium 15 - 30 which I use for bread and butter cars
Down from £9.99 to £4.99

I don't work for Havoline or Morrisons I assure you, just delighted not to pay £50 a gallon for the rather overrated Mobil 1... or similar synthetic!

[Jamie]

Are they any good for wet clutches?

[simon duval smith]

Well I always used a semi-synthetic (Fuchs Silkolene Sport 4) in my Baghira with the 660 Yamaha wet-clucth engine with no problems at all.

[Linegeist]

I use fully synth in my Skorpion with no clutch problems at all - even at maxi chat there's no slip. I think you'll find that synthetic oils aren't more slippery - they're just tougher and don't break down as quickly inside an engine.

[Anders]

Opening can of worms... pfft...

As long as the oil is formulated for motorcycle engine use, i.e gearbox and wet clutch, it does not really matter if it is semi or fully synthetic given that is meets the API requirement specified by the engine manufacturer.

I for one only use fully synthetic as it generally can be found at a price close to the semi stuff, and as stated before it does not deteriorate as fast as the semi or dino oil.

5W-30 seems a tad thin for a big single, 10W-40 would be more suitable, or even heavier oil unless you ride in really low temp conditions.

[Linegeist]

Hi Anders,

I remember reading a while back (on the Honda CX/GS Owner's Club IIRC) a piece by a pretty clever type, that the lower viscosity figure for fully synthetic oils was rather meaningless as, by definition, they are all very 'thin'. It went on the say that their real 'strength' lies in their ability to maintain viscosity at high temperatures while resisting shear at a molecular level for extended periods compared to their lesser cousins.

I'm very interested as to why a thick oil is more desirable in a big single.

Y'see, I've always been of the view that the greatest loadings in an IC engine are generally found at cam lobes, small end and big-end bearings.

Cam loadings are going to be the same on a single as any other engine, and the oil pressure at the big-end is going to be largely dependent on centrifugal force and flow rate once the engine's running. Given that our 660 engines are high-revving (for big singles) I'd have thought that, provided enough oil's present AT the bearing gallery at the time of load application (thin oil arrives quicker when cold), the centrifuge effect of ther spinning crank will immediately ensure a nice cushion of oil to keep metal to metal contact at bay.

I've a horrible feeling someone's going to tell me I'm talking out of my exhaust port here .......... but that's how I learn.

[Anders]

True, the lower value is pretty meaningless unless you ride and start your engine att freezing point or lower.

The higher value tells us the viscosity roughly at operating temperaure for the oil and this is the most important value.

Wide range multigrade oils should be avoided in mororcycle engines, but I think there are no such olis specifically formulated for motorcycles, an example of this would be a 0W-40 oil.

The way these olis work is that they have heat activated thickeners in them, the polymer chains are rolled up in ball of twine like shapes when cold and untagled when warm. The mechanical wear on the oil in the gerbox and clutch destroy the thickeners making the oil to thin faster than regular multigrade, this is not an issue in car engines however.

Thick oil in big singles is good for the case when you put power on at fairly low revs as the power pulses are far between, at higher revs it is not a problem. It is also well known that a good recipie for engine failure is to run the engine at power on low revs.

Also the bearing gallery is specifically designed to work best with a specific viscosity range, producing a good load resistant oil film, too thin oil will result in metallic contact regardless of ample supply.