What oil grade to use

[Red-Duc]

I went to a local dealer to get some belts and oil the other day and He said I should be using 20-50 in my bike instead of the 10-40 that I normally use, What grade oil is correct as I always understood 10-40 was correct

[Shazaam!]

If you look at the Owners Manuals recommendations you'll see:

SAE 10W40 for S4, 748R, ST (from 2002) 998/748 (2002) All newer bikes but still with old engine designs.

SAE 20W50 for 748/996, ST, (up to 2001) All older bikes

If you look at the Manuals temperature to viscosity chart, it is identical for all bikes so that has not changed but the recommended viscosity has changed. It could be because some time ago Ducati was sponsored by AGIP and they sold 20W50 oil. Now sponsorship is Shell and they sell both 10W40 oil and 20W50 oil.

ST4 and S4s engines are more or less identical except for camshafts and the S4 does not have an oil cooler. This means that the oil will run hotter in a S4. Still, Ducati recommended 10W40 for the S4 and 20W50 for the ST4; maybe they were too lazy to update the manual for the ST4.

The more interesting is the 748. When it was later included along with the 998 in the Manual, it suddenly went from 20W50 to 10W40 without any changes to the engine.

[ts-ts]

Heh.

Looked up this in my 1997 900/750/600 Supersport owner's manual, which (to my surprise) stated: "AGIP 4T SUPER RACING", with no mention of viscosity.

Looked up in the Haynes manual for these bikes ("2-valve V-twins '91-'96"): "Oil type: AGIP 4T Super Racing, or any good quality fully-synthetic motor oil. Oil viscosity: SAE 5W/40"

My oil level sightglass has stayed clogged up with emulsified water far as long I've had the bike (3 years), and has never cleared, even after long runs on hot summer days (left the bike to cool down with the oil filler cap off). I'd like to know if any particular oils (AGIP?) are better than others, when it comes to not keeping condensation emulsified in the engine?

[Shazaam!]

After a long ride at temperature, the crankcase ventilation system should have pulled off any water in the oil caused by simple condensation. You're seeing more water than that so I'd suspect that it's probably coolant that leaking past the water pump seal.

[ts-ts]

I'm not sure if the SS & Supersport section covers more bike models than I know of; but my '97 750 SS is air-cooled (luckily!).

But then again, the British version of "hot summer days" may not reach up to the standard required . . . .

I'd prefer to flush out the emulsified condensation with the old oil before filling the sump with top-of-the-line synthetic oil, but then again, perhaps high-tech additives in the latter is required to solubilise the condensation?

[chrisw]

This is still available from M&P at £24.99 delivered

http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=110890441982