V10 CENTAURO

bising wrote:

Was wondering whether our bikes share the same engine oil used on cars. Referring to TIPS, those names mentioned, eg Castrol GTX, are common engine oil for cars. Comments? Tks

Oh good - an oil thread!

Yes in principal - with some minor reservations about the actual specification being more suitable for our 'old fashioned' Guzzi OHV engines.

Why? - Conventional modern motorcycle engines have the engine and gearbox combined in a 'unit' construction. Therefore they must use specialist oils which can deal with the lubrication needs of the engine and also provide the extreme pressure (EP) values required for the gearbox cogs - and often the clutch assembly as well in bikes without dry clutches.

On the face of it this sounds like a good situation - only using one type of oil - until you realise that dedicated motorcycle oils can be much more expensive and almost invariably require changing at more frequent intervals.

As Guzzi engine and transmission assemblies are seperate entities - much the same as old style car assemblies - they can use oils which are formulated to function best in the different units. As you have noted, multigrade 'car' oil in the engine and EP oil in the gearbox and rear drive box. Benefits are lower overall costs of the oils and vastly increased service intervals - for the gearbox and rear drive at least.

I'd add that I feel more than happy that the gears are running in oils designed specifically to give higher shear strength, (85W-140 in my case), than engine oil multigrades.

Something else to consider is that it is being reported more often that the latest synthetic multigrades may not be the best selection for the older design of pushrod type engines - do a search on the forum and elsewhere for the reasons why - so cheaper semi-synthetic or dino oils might be better in our Guzzis with subtle differences between the hi-cams and other 2 valve engines of the same era. I'm sure that some recommendations will follow.

There's a lot of what I think is marketing and regulatory silliness going on with engine oils right now... the bike manufacturers have taken to recommending exorbidantly expensive oils, probably because they are in fact better at handling high temperatures, but equally (I believe) because they have marketing arrangements with the oil manufacturers. They have to get their oil for new bikes from somewhere, and I'm guessing they get it that oil for free if they write the right oil recommendation in the owners manual, and put the right sticker on the crankcase...

I was recently confronted with the spectre of a liter of motorcycle oil on a gas station shelf in Italy for 24 Euro... or roughly 37 US dollars per liter! Around $150 for an oil change! Total insanity from my point of view, and not something I'm going to get involved with. I've run my Guzzis for 100's-of-thousands of miles on what is now $3/quart 20W-50 car oil, and with all the hype right now I choose both the bike to ride and the oil in its crankcase with a certain level of critical thinking... Every bike is different, but marketing in the motorcycle industry has gone off the rails, and into orbit, in alliance with regulations that push towards oil viscosities closer to water than what the engine really wants: 5W oil, regardless of its stability in modern synthetic multigrade form, was not invented because your engine likes it.

That's the way I look at it, and act on it