Oil Issues

[BajaRon]

Good stuff!! Just a couple of points to clarify..The bottom viscosity number is what we should worry about. The high number is only what it's been stretched to behave like and this number diminishes as mileage is added. Other issue is that these "close" tolerance Rotax engines are using fairly significant oil between changes. Most folks write these off due to operator dipstick errors because of the dry sump but they do actually use significant oil for low time water cooled engines. Could this be a sign of too low a viscosity oil being used?

This 'bottom viscosity number' issue is true for oils that need viscosity modifiers (additives) to keep them from getting too thick when cold. But it is not accurate for True, Full Synthetic Oil. True synthetic oil does not need viscosity additives because it does not thicken much when it gets cold (as does standard oil or fake Group III synthetic oil).

There are very good articles regarding this on the web. Here is a portion of one. I have edited it to make it shorter. You can read the entire article here; http://www.upmpg.com/tech_articles/motoroil_viscosity/

What about synthetic motor oils? Do they need Viscosity Additives?
Group IV (4) base oil (synthetic) is chemically made and does not need Viscosity Additives. However, in recent years Group III (3) based oils have been labeled "synthetic" through a legal loophole. Group III (3) "synthetic" motor oils must employ Viscosity Additives being petroleum based.

Group IV (4) PAO based synthetics make the best motor oils. They are compatible with petroleum based oils and fuels plus they have better seal swell than petroleum. Typically PAO based motor oils use no Viscosity Additives yet pass the multi-grade viscosity requirements as a straight weight! This makes them ideal under a greater temperature range. One advantage of not having to employ Viscosity Improving additives is having a more pure undiluted lubricant that can be loaded with more longevity and performance additives to keep the oil cleaner longer with better mileage/horsepower.

How do I know what motor oil is a Group IV (4) based PAO synthetic motor oil?
Many large oil companies switched their "synthetic" motor oils to the less expensive/more profitable Group III (3) base stocks, including Castrol Syntec.

 

[flybuddy]

Good info---what about oil loss? What do you think the cause of high oil consumption might be with these engines as there are quite a few folks that have pointed to this as an issue.

 

[BajaRon]

Good info---what about oil loss? What do you think the cause of high oil consumption might be with these engines as there are quite a few folks that have pointed to this as an issue.

I don't have a good answer for this. The Rotax does seem to use more oil than you would expect but the amount seems to be all over the map. Some use a lot, some not so much.

The obvious answer would be oil getting by the rings. But there is more than 1 reason this may be happening. I wonder if lugging the engine might increase oil consumption.

Overfilling may be the cause in some cases too.

The type and viscosity of oil can also be a factor.

I've used 10w-40 Amsoil in my Spyder since early on. It's got 31K on it now and on our recent 6,000 mile round trip from East Tennessee to California I used a total of less than 1/2 quart. I did not change oil so I don't think that's too bad for that distance. Several days we traveled all day in triple digit temperatures as well.

 

[bruiser]

My phaser device doesn't use oil. It uses phased ion dilitium crystals. :roflblack:

 

[BajaRon]

My phaser device doesn't use oil. It uses phased ion dilitium crystals. :roflblack:

Really! Does it look like this?