Engine oil level.

[Twin Pinzies]

I have noticed over the years that my Pinzgauers run far better when the engine oil level is at the 1/4-1/2 mark on the dipstick. Before, I would routinely fill them to the 3/4 mark after changing the oil but now I shoot for the lower end of dipstick. Since doing this, I have killed some annoying "gremlins" that were plaguing me (as soon as I lowered it).
Has anyone else noticed this? Why would this happen anyway?

Note: My trucks only run in the summer months with 20W50 conventional oil. They climb and descend STEEP grades every day... over rough terrain... loaded... at elevations between 9,000 ft.- 13,000 ft. if that helps make any sense.

[ka]

i just started to wonder about oil weight. book only states 15w-50. so 20w-50 is ok? even in winter?

[Twin Pinzies]

I don't use my trucks in the winter so I have no idea how 20W50 would do. Probably badly! It's the best for summer use IMHO.
I was really wondering if anyone else has ever noticed that these trucks run better with less oil in the crankcase.?!?

[ka]

well i can tell you mine seems to run normally (the same) with very different levels. filled and more than a quart down is the same.

[M Wehrman]

The crankshaft splashing in oil will create some drag,which would explain the improved running when slightly low. Race cars have run dry sumps over the years,also deeper sumps to increase oil capacity and to keep the oil away from the crank. All little tricks to get a tad more power.
Mark

[Jim LaGuardia]

Here is why oil level can impact your running problems.
1. Your piston rings and valve guides are worn
2. Scavenge pump pipe may be fractured

At severe nose down angles it is the job of the secondary(scavenge) oil pump to keep oil from pooling flooding into the #1&2 cylinders. When the pump cannot keep up you will get a large blue/white plume of smoke, this is oil flooding past the rings and exhaust guides
So Twin Pinzies, that is why the synthetic oil fouled your plugs worse than Dino oil

I have repaired or replaced several scavenge pipes in the last few years.
The replacement requires a complete teardown as the engine case must be split.

[Twin Pinzies]

Thanks Jim. That just makes plain sense. You're the man!

Should I plan on rebuilding both of my engines this winter? Or just run low oil?

[Jim LaGuardia]

If you rebuild them, they will last many more years. Start with a compression check, anything under 120psi is not good. A fresh engine will usually be 130-160 psi.

[drawe]

Something just kicking around about air cooled engines in general: The oil can actually serve as a 'coolant' to help move some of the heat away from the 'vitals'. I did think about the dry sump system as well, but how hot would the oil tank reservoir/scavenge get? I think/feel that air cooled engines are designed the way they are and specs are developed to meet the environment they are to operate in. This may sound corny , but these are just my thoughts.

Dave