Ive noticed that every time the oil in m TJ VRX drops slightly below the lower marking on the dip stick that my fuel economy dramatically increases (talking minimum 1l/100km better). last few fills have been 10W/30.

Im obviously not going to leave the car with little oil to see better returns on fuel, but I may not fill to the upper line on the dipstick any more either. Anyone experienced this before? Anyone have a good explanation for its occurrence?

Interesting. I suppose less oil would make oil hotter and more viscous > less friction. Fair increase in economy tho!

It's psychological - you know that the oil level is below the minimum mark so you subconsciously drive a bit easier to avoid damaging the engine and use less fuel.
You answered your question yourself when you said "Im obviously not going to leave the car with little oil to see better returns on fuel"

How many Km's has your engine got on it? My VRX's oil doesn't move off the full marker

the correct oil level is also important for cooling the engine so leave it at max.

It's psychological - you know that the oil level is below the minimum mark so you subconsciously drive a bit easier to avoid damaging the engine and use less fuel.
You answered your question yourself when you said "Im obviously not going to leave the car with little oil to see better returns on fuel"

ah yes, but i only deemed the oil to be low after the resulting increase in economy :)

my vrx is just about to turn over 200k and drops from the full marker to the low marker in about 2 months of driving, which isnt bad at all so im not worried. It isnt the first time that economy and low oil have coincided, otherwise I wouldnt have made the relationship between the two.

I wouldn't say going from high to low in two months is good....

My TJ with 220k on it would sit at full until you opened up the drain hole. :eh:

well its certainly not brilliant, but its far from overly concerning