Here's a good question. Why is 10W40 so bad? I know people say that since it has a larger spread than a 10W30 (30 points instead of 20) that it can break down a lot faster and cause sludge, ect... But my arguement to that would be this: almost all Honda, Kawasaki, and Suzuki motorcycles recommend 10W40 motor oil for their motorcycle engines. Now remember that an oil for a motorcycle must lubricate BOTH the engine and transmission, operate in higher temperatures, operate in a higher RPM range, and most are air cooled. Also, like my brothers Honda, the motorcycle has no oil filter. On top of all this the manual for the Honda recommends changing the oil every 4 months or 4000 miles.

It seems to me that oil for motorcycles would get a pretty good workout. Plus no oil filter and a longer OCI and you get the picture. I just can't believe the bad claims of a 10W40 if it has to be used in these conditions without breaking down. What do you guys think?

Oh on a side note I have another good question. My car manual says you can use 5W30 from 32F and anything below (for really cold weather as in -10F, -15F, ect...) It recommends not using the 5W30 above the 32F mark. It also states you can use 10W30 from 0F - 100F+. My question is why can't you use 5W30 when its 80F outside? They are both 30wt. oils when at operating temp. It seems to me the 5W30 would only be icing on the cake - better flow on start up. Is it because the 5W30 can shear down more than a 10W30? Someone please comment on this. Thanks everyone.

 

actually the streetbikes have oil filters and alot of the fourstroke 4 wheelers and dirtbikes do to, I assume you are talking about a 2 stroke dirtbike? I've never seen an oil filter on them. I guess thats why they recomend changing the oil after every 3 races...atleast thats how I do it. Maybe the two stroke bikes dont have oil filters because oil only has to lube the bottom end, you have oil in the gas to lube the piston and all that. The other day I was driving my aunts van when I stopped at the bike shop and noticed the van was ticking a bit. The oil was low and there werent any gas stations or anywhere to find car oil so I just threw in several quarts of Silkolene 20W50 motorcycle oil, no problems yet

 

No the motorcycle is a 2003 Honda Rebel with the 250cc 4-stroke engine. It is a street bike but it has no oil filter and recommends 10W40 with 4 month or 4000 miles oil changes. Also this bike is mainly ridden on the highway at 55 - 65 mph. Now for a 250cc bike this is pretty hard on it. The RPM's are getting pretty darn high when your going 65 mph and you have a 200 lb. person on the bike. Anyway I don't think a 10W40 can be as bad as some people say if the oil has to go through this without shearing down and sludging up.

 

Honda has recommended 10W-40 for 30+ years. After seeing oil tests in Motorcycle Consumer magazine, you would be better off with a 15W-40 oil like Delo or Rotella, or a synthetic. The reason is that those transmission gears shear down conventional 10W-40 in less than 2000 miles.

It is also important not to use an "energy conserving" oil in a motorcycle with a wet clutch. The friction modifiers cause clutch slippage.

On your second question about 5W-30 vs 10W-30 in hot weather, while both are indeed the same viscosity at 100C when new, conventional 5W-30 is more likely to oxidize, shear and evaporate at high temperatures than a similar 10W-30 because of the thinner base oil used.

Jim

 

I wasnt aware than the Rebel didnt have an oil filter...you learn something new every day I'd use motorcyucle oil in the bike. Try something like Maxima 10W-40, 20W-50 even Honda's very own motorcycle oil like the GN 4.

 

Currently using the Honda GN-4 in the bike but it's pretty darn expensive. I don't really think that motorcycle oils have that much better of an additive package or base oil than the manufacturer tries to tell us. There have been many people that have used Castrol GTX 10W-40 and 20W-50, and Mobil 1 15W-50 for years and years in their bikes without a problem. But I guess thats a topic for elsewhere.

 

cocnerning motorcycle oil...
here is a thread from the past you can refer to:
https://www.ford-trucks.com/forums/s...d.php?t=112348

FWIW - I use Shell Rotella 15-W40 exclusively in all my motorcycles now.
I'd imagine others (ex. Chevron Delo) would do just as well.

 

i wonder why Yamaha reccomends 10-30 instead of 10-40? for the summer they reccomend 20-40. also i use the much-to-epensive yamalube, anyone have any eperiene with it?

 

as for the yamalube my brother uses it in his r-6 and hasn't had any problems. with two strokes the oil in the gas lubricates the crank bearings and the piston. the only oil you have to put in the bike is the tranny. i'm not shure about the honda rebel but take a look on the bottom of the crank case there should be a drain plug and another big plug about 2 inches in dia. if the big plug is there thats where you will find the oil filter eleament. it's not a canister type. as for dirt bikes and four wheelers most newer ones come with oil filters the older stuff didn't. in my bike (kdx 250) i changed the oil once a season (summer) untill i started racing then it was once every 2 races. if you ride in deep mud or water change your oil more often bottom ends and trannys aren't cheap. if i remember right the yamalube is syn.

 

i belive yamalube is paritially syn but not completey beaue of the clutch slipping issue with dirtbikes. im very happy with it also and i dont have to hange it but every few months. i notied that yamha says to hange the oil every 3000 miles on mine but i do off roading moslty and the oil gets dirty much sooner than 3000 miles so i end up haning it every few hundered miles.

 

Auto manufactures don't recommend 10W-40 because of the spread between to 10 and the 40. To make a multi viscosity oil, oil manufactures add a polymer (plastic) to a base oil. In the case of a 10W-40, the base oil is a 10 weight oil, or something close to it. The Polymer are coiled shaped pieces of plastic that uncoil as the oil heats up. When the oil is cold, the polymers are coiled and short which is similar to a low viscosity oil. As the oil heats up the coils start to uncoil and become long, simulating a higher viscosity oil. In order to achieve a 10W-40 weight oil, a lot of these polymers are added. Over time the polymers break down. In the case of a 10W-40 since it contains more polymers then a 10W-30, the effects of the polymers breaking down are more pronounced. In other words, 10W-40 viscosity breaks down much faster then other oils. And since most auto manufactures "recommend" leaving you oil in the crankcase for 5,000 to 7,500 miles (varies with mfg'er), 10W-40 oils just aren't up to the task.

 

Another factor has also entered here.

That is that the weight designation is now used to specify oils which are designed for emission control and/or energy efficiency (eg.: 5W20), even if their absolute viscosities would fall into existing categories.

The 10W40 oils, particularly synthetics and blends, are probably now able to handle the spread, but the Feds don't want them used for other reasons.

 

Changing the motor oil on a 2 stroke huh. I think you would have a hard time with it, unless we are talking about the transmissions lubraction here.

 

And what might those other reasons be?

 

I would think fuel mileage would be the largest reason.