Oil Mix - 50:1 or 40:1 ?

[pferreira1970]

Hi,
I own a 1998 GG ec250…

When I mix the oil and gas I usually do a 50:1 oil ratio as mentioned in the motorcycles owners manual, but I notice many of you do 40:1 and other blends!!!

Should I be doing 40:1 versus the 50:1 as suggested in the manual?

Can you give me the pros and cons on 50:1 or 40:1 ?

Thank you,

Peter

[JEEPUSAURUS]

I have been running 50-1 for the better part of 20 years, when i was racing and having my engines done by tom morgan racing he recomended no leaner than 40-1, so i compromised and ran it at 44-1, Never had any problems with either one of these ratio's. As long as you are running a quality oil i don't feel that 50-1 is a bad thing, Heck one of the guys i ride with has been running cenex tc501 in his 97 wr 250 @ 50-1 since it was new and hasn't changed rings or piston in at least 6 years, still runs good. so it really is probably just a matter of preference, and if 50-1 wasn't good enough, the factory wouldn't say 50-1 in the manual.
Just my 2 cents.

[eff]

I run 50:1 full synthetic.

[WoodsRider]

Back in the old Smackover forum days Jim Cook used to preach that running a 40:1 ratio reduced piston ring wear. At the time I was using Mobil MX2T @ 50:1 and after a full season my piston rings were beyond the factory wear limits. After rebuilding the top end I switched to a 40:1 ratio. After a full season on the new piston and rings I tore down the top end and the rings were still within the factory wear limits. I replaced the rings anyway.

There's been some discussion about the 50:1 factory recommended ratio being more for reducing the *evil* smoke in order to meet Euro emission standards. Personally I'm sticking with 40:1 in my Gasser and 32:1 in my vintage bikes.

[Eric K]

More oil = better ring sealing and less wear.

My 2 data points...

Top ring end gap increased 0.006" in 91 hours at 50:1

Top ring end gap increased 0.001" in 49 hours at 38:1