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That is only sometimes true. It depends on what type oil is used. That is because synthetic oils slow down the burn rate and castor oil speeds it up. So if your engine needs a faster burn but you switch to fully synthetic oil then it will slow it down. I recommend synthetic/castor blends or 100% castor products for race bikes. If your engine needs a slower burn then you should use a full synthetic product. The higher the RPM the quicker the burn has to be which is why squish velocity has to be higher for high RPM engines. High compression quickens the burn but causes too much pumping loss on high RPM engines. The higher the exhaust port is, the quicker the burn has to be because that gives less time for the burn to complete before the descending piston opens the port.
"But I've been told that more oil helps the rings to seal better"
To a degree that may be true if you were dumb enough to break in your new rings with synthetic oil. You have to use mineral oil to break in rings. Synthetic oil is too slick. It doesn't allow the needed friction to let the rings wear down to conform to the cylinder. If the rings are sealing good and you are using synthetic oil at 32/1 (in an engine reving no more than 10K) then you are causing excess viscous friction, which is friction due to high viscosity in an engine that doesn't get hot enough to lower the oils viscosity enough.
"But all the previous tests showed that more oil produces more power"
Maybe they did but we don't know:
1) if they correctly compensated for the change in gasoline % by jetting changes
2) what type oil they used on what type engine. If they used castor oil on engines that needed a quicker burn then of course they got that result.
3) whether or not the engine they used had been properly conditioned with mineral oil during break in.
Newest Test Showed More Oil = Less Power
I tested my air cooled 48cc for uphill speed with Motul 710 (2/3 synthetic) at 55/1 and 35/1 after correcting jetting (main jet and needle height) for the different ratios % gasoline change and found that more oil gave less speed. My engine doesn't have a squish band and so obviously needs a faster burn, not the slower burn that more synthetic oil provided. My next test will be with mineral oil vs mineral oil and castor oil blend.
There Is No Blanket Rule That Excludes Oil and Engine Type
This topic is more complex than what we thought it was. It's not just about how much oil is used.
There Is No Rule That Applies To All Engines Other Than "MATCH THE OIL TO THE ENGINE"
This is the only intelligent approach.
"But I've been told that more oil helps the rings to seal better"
To a degree that may be true if you were dumb enough to break in your new rings with synthetic oil. You have to use mineral oil to break in rings. Synthetic oil is too slick. It doesn't allow the needed friction to let the rings wear down to conform to the cylinder. If the rings are sealing good and you are using synthetic oil at 32/1 (in an engine reving no more than 10K) then you are causing excess viscous friction, which is friction due to high viscosity in an engine that doesn't get hot enough to lower the oils viscosity enough.
"But all the previous tests showed that more oil produces more power"
Maybe they did but we don't know:
1) if they correctly compensated for the change in gasoline % by jetting changes
2) what type oil they used on what type engine. If they used castor oil on engines that needed a quicker burn then of course they got that result.
3) whether or not the engine they used had been properly conditioned with mineral oil during break in.
Newest Test Showed More Oil = Less Power
I tested my air cooled 48cc for uphill speed with Motul 710 (2/3 synthetic) at 55/1 and 35/1 after correcting jetting (main jet and needle height) for the different ratios % gasoline change and found that more oil gave less speed. My engine doesn't have a squish band and so obviously needs a faster burn, not the slower burn that more synthetic oil provided. My next test will be with mineral oil vs mineral oil and castor oil blend.
There Is No Blanket Rule That Excludes Oil and Engine Type
This topic is more complex than what we thought it was. It's not just about how much oil is used.
There Is No Rule That Applies To All Engines Other Than "MATCH THE OIL TO THE ENGINE"
This is the only intelligent approach.
