I have 2 new one gallon motorex oil 10-50w full synthetic that was for my ktm 530 exc and since I sold my ktm, I was wondering if I can use the 50w? I understand once I switch to full synthetic, I can't go back. I have about 5000 miles on my 09 klx250 right now.

 

You can't go back to regular oil after running synthetic?

 

I have the same question as dan888. I would like to see some written proof you can't switch back. If anybody has a link to that information I would like to read it. Anyways, If you look in the manual there is a chart of acceptable oil weights for given operating temperatures. I think your safe, at least in the summer.

 

The owners manual should have a temperature range for different weights of oil. I can't remember the details off the top of my head, but basically if it is above freezing, you'll be fine.

 

From the Mobil 1 website...

"Can different synthetic motor oils be mixed together?

Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way."

Although it isn't specifically talking about Mobil 1 for motorcycles, the same rules apply. Changing back to conventional oils will result in more frequent oil changes...

 

You can switch back and forth at any time. It is a myth that you can't.

A 10w-50 oil is perfect mix for hard driving in any season. 10w-40 also for any season. 10w-30 recommended for winter use or colder climate (below 70*F). 20w-50 for summer use or warmer climate (above 70*F).

The 50 weight oils provide the maximium proctection for hard, off-road driving. The 40 weight oils provide the normal protection for normal driving. The 30 weight oils provide better startup protection and thinness at cold temperatures.

 

I guess I was given the wrong information by a trusted mechanic regarding the switchiing back. Thanks for inputs guys!

 

I use Rotella-T 15W50 I have never had any problems. The KLR guys swear by the stuff...I do to I guess.

 

ok, with the 10-w50, its not weight, its the rating at temps. the numbers are call the SAE rating, i will find some more links on this.

now the ratings assume that the air temp has a relationship with engine, this is true, as on a cold day your engine stays cold, and on a hot day your engine is more likely to over heat.

so the wider the better, if you are in a colder climate then you would go for a lower temp oil and if your in hot climate then a hotter rated oil. the reason why you warm up your bike besides the expansion from heat, is to warm up your oil, if you have ever done an oil change on a hot bike compaired to a cold bike, the oil is thinner in the hot bike and thicker in a cold bike.

so when your bike is to cold for the oil rating, oil is thick, slow to move and dense, engine to hot for oil rating then it will be very thin, poor lubrication properties, and not removing heat properly.

there was a question of mixing oils, never mix oil, the additives in them to produce the wider operation temp may not mix etc but in saying that its better to mix oils and get home and then do an oil change.

hope it helped

 

this was sourced form http://www.volvoclub.org.uk/engine_oil_history.shtml

eg. 10w50. this is the rating for the second number.
so as you can see this oil (10w50) has a viscosity of 16.3-21.9 at 100°C

Viscosity of Engine Oil
Viscosity @ 100°C

cst SAE rating

16.3 - 21.9 = 50

12.5 - 16.3 = 40

9.3 - 12.5 = 30

5.6 - 9.3 = 20

less than 5.6 = 10

"This system worked very well and is still in use today. SAE 30 became accepted as the standard for engine oil, giving reasonable film strength for the white metal bearings of the day. This weight oil was usable down to around minus 10° centigrade before it became too thick to move round the engine, which covered use in the majority of situations around the world."

ok now for the 1st number out of our example (10w50)

Low temperature rating
Temperature at which oil is usable

25w = -5°C

20w = -10°C

15w = -15°C

10w = -20°C

5w = -25°C

0w = -30°C and below

so our oil (10w50) has a minimum working temp of -20°C.
our klx must have a ablest a SAE rating of 40 so an SAE rating of 50 is fine

all the tables are from http://www.volvoclub.org.uk/engine_oil_history.shtml
that will tell more than what you want.