20w40

So I know we can use 20w50, and that's what I use since it's all I can find, but I've thought that I would like to order some 20w40 at some point for my next oil change and use that instead.

Does ANYONE here actually use the recommended 20w40? Anybody have comments to make on the potential difference on that? Anyone able to explain what the "20" and "40" actually each mean? I know somehow the higher numbers mean it's more viscous than, say, 10w30, the oil we should use in colder weather (fluids are less viscous at lower temperature, so that makes sense), but why there are two numbers, and what the numbers are actually a measurement of, I do not know.

Just would love to educate myself, is all. Maybe chacal sells 20w40?

 

I buy the Mobil 20w40 at Advance Auto Parts or you can get it at Autozone. 20w40 means that the oil will not get heavier than 20 when cold and not thinner than 40 when hot.

 

Advance doesn't sell it where I live. Haven't found it anywhere here, actually. They only have valvoline 20w50 (and some of them have a Castrol one).

Did you mean not thinner than 20 when hot, 40 when cold? I thought lower numbers meant thinner...

Does it have to be motorcycle oil, or just have to not have friction modifiers and not be synthetic?

 

The higher the number, the thinner the oil.
Motorcycle oil, no friction modifiers. Some say that synthetic is great, hadn't tried any myself.

 

Wrong way round mate....90 weight= gear oil!

 

Your right! I'm going to sleep now, it's 5:13am here.

 

Multi-weight oils are formulated to "behave like" a thicker oil when they get up to temp; in other words, 20W50 is a 20- basis weight oil that when hot, behaves like (hot) 50 weight.

Automotive oils are formulated to SAE standards, ie: SE, SF, SG, etc. Motorcycle oils meet JASO standards. We avoid automotive oil because the latest automotive grades, by definition, contain friction modifiers. Ten years ago this wasn't the case, let alone 30 years ago.

I actually do run 20W40 in my 550s, although I generally use 20W50 in the hottest part of the summer, if the oil changes "stack up" in my favor.

 

My understanding of oil:

Oil viscosity is called weight. A higher number is more viscous. Of course the viscosity changes with temperature (high temperature is much less viscous).

The American Petroleum Institute has standards for the testing of motor oils. The standards include a low temperature and high temperature test.

A 20w40 oil has the viscosity of a 20 weight oil cold and a 40 weight oil when hot. This is accomplished with additive molecules that become more viscous when hot.

Those additives break down. Eventually that 20w40 oil just becomes 20w. I've read convincing articles that running the oil through the transmission of a motorcycle breaks those additive molecules much faster than happens when used in an engine only.

Synthetic oils need less additive to achieve the multi viscosity rating and degrade more slowly. Their chief advantage is the slower breakdown lets you extend the change interval.

A lot of people run diesel truck oil in their motorcycles (Rotella-T is probably the most popular). It's readily available in 15w40 so it doesn't thin out as much with wear as a 10w40. It has lots of zinc and other additives that are good for the engine but can't go into car oil because of catalytic converters. It's way less expensive than "motorcycle" oil.

 

that's a little backwards, link.
if you can't see your breath, forget the first #

 

Why don't we try to find 10W-50 and then we never have to change grades of oil up here in Canuckville @ fall.

 

I was briefly on some old Suzuki GS forums before this forum, and everyone there ran the diesel oil. Is that advisable for our bikes? That sounds ideal to me--give the engine some good stuff, cheaper, lasts longer...

 

this is what i put in all my bikes and most of the cars.
best part is i can have the wife pick it up, there is only one kind

 

I have an unopened 55 gallon drum of Citgo 500 Oil. It was ment for diesel engines 15 years ago. It had a diesel rating of CDII and a gasoline SAE rating of SG. It is 30W. Being a SG oil it probably has more zink in it than you should use in a late model vehicle with a catalic converter. It would be a great break-in oil for engines without a catalic converter. I have been thinking using it as a summer oil for my bikes. Any thoughts?