Best Oil

[opnea]

I got an old machine and i’m not sure whether i should run a little thicker. It’s almost 35 years old. Might go 20w-40 

[Mech]

Thick oil doesn't help bikes with roller crank bearings, they need good oil flow, not pressure. I'd stick with the manufacturers recommendations for your temperatures.

[Gwbarm]

Good point Mech! I usually run a thicker oil in an engine that has been sitting for years on first start up to get everything oiled and lubed up and turning again, run it for a while to hopefully get the inside cleaned up  good, thicker seems a little stickier than thin, probably not, but thats what i do. Then change back to manufacturers grade after running for a month or so.

[Mech]

Thick oil helps in a worn engine that has white-metal/shell bearings, but it doesn't help with roller bearings, and if it's in a cold climate it can get pumped slow at startup and it can even strain the oil pump.

I think people have heard that thicker oil helps in old cars.. and so assume it will help in a bike as well.

[puskinelis]

I wouldn't experiment with different specs way off, but minima difference might improve. I would recommend use fully synthetic instead of Half-synthetic that will help for sure. Mine oldy moldy honda foreman 450 OEM recommendation 10w40 half synthetic, but I use fully synthetic, I think it's especially good for this bike for example as it uses oil cooler. And it heats up and cools down every second trhough cooler, which synthetic oil doesn't loose it's spec, but half synthetic might burn or downgrade a little more.

Edited March 8 by puskinelis

[Gwbarm]

I still use conventional oil in my old worn bikes, i use fully synthetic in my autos, but my expierience with synthetic in older engines is that it seems thinner than dino oil of the same grade and in older worn bikes they tend to use more oil if switched to synthetic. I dont race or really abuse the engines but i have still noticed using more oil if switched to synthetic, i have never really understood the reasoning behind half and half oil and never used it. 

[Mech]

Modern car engine's have minimum amounts of oil in their sump, extreme temperatures in the engine and under the bonnet, especially if they have a turbo, they have incredibly fine clearances everywhere, shell bearings, high stresses, require high oil pressures from cold to hot, and they rev high, and from cold often. They also have stringent emission requirements.  They need good oil, and synthetic oils are particularly good with the high temperatures.

Bikes on the other hand, even air cooled bikes, are low temperatures, low stress, roller bearings, mild power, low oil pressure, generous oil capacity, few emission requirements. They have very simple and low spec requirements for their oil compared to car or truck oil. In my opinion mineral oil is plenty adequate for them.

[puskinelis]

9 minutes ago, Mech said:

Modern car engine's have minimum amounts of oil in their sump, extreme temperatures in the engine and under the bonnet, especially if they have a turbo, they have incredibly fine clearances everywhere, shell bearings, high stresses, require high oil pressures from cold to hot, and they rev high, and from cold often. They also have stringent emission requirements.  They need good oil, and synthetic oils are particularly good with the high temperatures.

Bikes on the other hand, even air cooled bikes, are low temperatures, low stress, roller bearings, mild power, low oil pressure, generous oil capacity, few emission requirements. They have very simple and low spec requirements for their oil compared to car or truck oil. In my opinion mineral oil is plenty adequate for them.

I agree. Especially modern engines with EGR system are contaminated after a few hundred of km or miles. But engines which doesn't have EGR like bike engines are always clean brown even after thousands of kilometeres. But! I wouldn't agree that bikes do not need synthetic, because with the car you usually drive with no rush, on low RPM so engine and oil doesn't stress and degrade. With the bike you go full throttle and then stop, full throttle and then stop, it's play thing. Also you don't change engine oil so often so longetivity of synthetic wins there again.

Edited March 8 by puskinelis

[Riki]

I think castrol makes best oils