I bought my bike used and the seller said he used synthetic oil... So is it correct I can NOT switch back to regular oil?

Also is mobil 1 synethic in a 10w40 the same for cars and bikes, or do I need to go to a bike shop to get special oil?

 

You can go back to using non-syn oil and it's ok.
Do not use oil suitable for cars in bikes. There arefriction reducers in car oil that will harm your clutch - make it slip. You don't want to use oil that has moly additives.

 

That's not quite right!

The onlyauto oils you cannot use are the oneslabelled as Enery Conserving. Any other auto oil is fine as long as its the right viscosity for your environment.

 

I have also heard (from sources I'm inclined to trust) of 'friction modifiers' used in some car oils that can make your clutch slip... this is in addition to the energy conserving stuff. car oils without this other stuff are ok for bikes... but why save a couple of bucks on a 3000mi event? You get pro honda oils for something like $17.
Again as far as I know, synthetic oils only last longer, since they're synthetic and dont lose their composition over time. They dont really have any other effect.
Also, 10w40 is great for 'normal' temperatures, but if you live in consistently hot / cold climates, then you could use other viscosities too... a 10w40 is viscosity 10 (low) when cold and 40 (high) as the engine heats up. If your ambient temp is consistently high then, you could use 30w40 too...

which brings me to a related question:
What happens if you slightly over-fill oil? My bike was on it's side stand and the oil-level window was empty... so I kept putting oil untill all my 4 quarts were over (I think the recommended is 3.6 or something). Then I straightened the bike and the oil went above the high mark, in fact filled up the whole window. I didnt drain the extra oil... does this cause the bike problems?

 

True, some you can use, but I never would. The Energy Conserving AND ones with Molybdenum Dimulsifide will render your clutch useless. As far as the motor/tranny is concerned, they'll all work. It's just because of the wet clutch that you don't want to use the other stuff.
I also don't see why people want to cheap out and run pennzoil, castrol, etc ^ when you can spend just a few bucks more and you'll get exactly what the bike left the factory with. I also see people running different weight oils too - when the bike's internal tolerances can only effeciently handle a specified viscocity.

 

So it WOULD be ok to switch back to the GH4 or what ever it is that honda sells?

Also is the car mobil 1 synthetic suitable for a bike or does it had the modifier stuff?

 

I think the mobil 1 for cars has the stuff you don't want in it, but I could be wrong.

Stick with GN4 or HP4

 

Also if your stuck on using Mobil 1. They make a motorcycle oil. I think its (dont quote me here)
MT4XT. This is specific to the 4 stroke engine. They also make a racing motorcycle oil. You can get this stuff at your local parts store, or at least AutoZone for like $8-$10 buck /per quart.

 

Where are you guys getting your information???? Even the Honda's HP4 synthetic oil has molybdenum in it.

Mobil 1 15W50 auto oil with the gold cap (replaced the one with the red cap)
- 97 F3 sold at 78k miles and its still going strong (I'm friends with the new owner)
- 05 600RR currently at 18k+ miles

That oil is fine for bikes as long as the viscosity suits your needs. One of my buddies has a 96 F3 that's going on 85k+ miles and he uses some cheap *** supermarket dino auto oil.

For me, its not an issue of cheaping out as you so eloquently put it. I refuse to pay$8/quart (or however much they wanna rip you off for) for a dino oil when I can get a synthetic oil for much cheaper that will do the job. Is the motorcycle-specific oil better? That's a debate that'll never be resolved in either of our lifetimes. But even if it is better, that's not to say that an auto oil isn't sufficient.

I am, by no means, telling you how to spend your money. But I'm presenting here some real data that says auto oil will work fine (again, assuming its the right viscosity and not Energy Conserving). Can you do the same???

Are you serious???????? Generally speaking viscosities operate within a certain range. And many viscosities overlap, especially the mulit-viscosity oils. The bike is not designed to only efficiently handle a specified viscosity. That's a load of BS! Nobody designs an engine around a specific viscosity. A viscosity is chosen for the engine, not the other way around.

 

um...look at the oil for bikes...some have molybednum in it!
i too use car oil...and based on personal research and experiene, i'm convinced that as long as it's not labeled energy conserving then it will do the job...as far as synthetic car or dino car...synthetic will last longer. just change regularly before your 10-40 turns to 10-20 or something and you will be fine.

yes, everyone is entitled their opinions, but please support with facts and not gimicks, etc...so when there are facts for snake oil...i will buy tons.