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Author Topic:   Fuel-Oil Mixture for Newer Yamaha Two-Cycle
fittongr posted 04-01-2009 11:26 PM ET (US)   Profile for fittongr   Send Email to fittongr  
[For a] 2006 Yamaha 25-HP two-cycle, what is the proper mixture of gas and oil? [When I] bought the motor, the dealer said to use a 50:1 mixture. [When I] showed him the 100:1 sticker on the side, he said it was mislabled. [The] owner's manual says 100:1, but [I] wonder if [Yamaha] is just trying to get better emissions. [Would] it be better for my motor to run at 50:1? [Would] it last longer at 50:1? [Thanks]
Clark Roberts posted 04-02-2009 07:05 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
100:1 is correct ratio! I have had 4 of these engines and always used above ratio and put on lots of hours. Two of my engines were oil injected so not a concern. Now, 50:1 would be ok, I think, but a waste of oil! Beam me up... Clark... SCN
TransAm posted 04-02-2009 07:25 AM ET (US)     Profile for TransAm  Send Email to TransAm     
I would use the manufacturers recommendation of 100:1. If 50:1 were acceptable, it would say so in the manual. Will 50:1 cause your engine to blow up? Probably not. But you will likely be fouling plugs more often and receive decreased overall performance, not to mention the extra expense of the oil itself.
jimh posted 04-02-2009 07:55 AM ET (US)     Profile for jimh  Send Email to jimh     
With such a high ratio of gasoline to oil, be sure to use good oil to lubricate that motor.
Tom W Clark posted 04-02-2009 09:15 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
If you use the motor quite frequently, the 100:1 ratio will be fine. If you use the motor infrequently, I would hesitate to use so little oil.

OMC went to a 100:1 gas/oil ratio in the late 1980s for their non-VRO models. The motors ran fine and used only half as much oil. But a problem developed when a motor was not used very often.

There was so little residual oil left on the cylinder walls, corrosion or rust would begin degrade the cylinder surfaces of motors left unused over along period of time. Motors run daily, or near so, did not suffer this problem.

OMC went back to the 50:1 recommendation and recommended the motors sold with the 100:1 stickers and manuals do the same as well.

Again, motor that were used a lot and spent little time between operations were not affected.

fittongr posted 04-02-2009 12:09 PM ET (US)     Profile for fittongr  Send Email to fittongr     
tom, thanks for the reply, solid information.
Tohsgib posted 04-02-2009 01:43 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Tom is dead usual. I usually ran my Yamahas with 75:1 just to be sure. 50:1 is probably overkill.
weekendwarrior posted 04-02-2009 04:29 PM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
check the manual to see if it specifies a specific oil or specific type of oil for the 100:1 mix.
TransAm posted 04-02-2009 04:36 PM ET (US)     Profile for TransAm  Send Email to TransAm     
Virtually all Yamaha manuals (I have yet to see one that doesn't) will specify Yamalube. They may also suggest that other TC-W3 rated oil is acceptable.

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