Burning oil on the highway?

[poteau]

I have a 7 bolt with a small 16g it's an EVO 1 engine. When I drive around on the highway long distance, I burn a lot of oil. Like a quart of oil per fill-up. Driving around the city all summer I wasn't having to top up at all.

If I go more than 1.75 tanks of fuel, it is enough to cause some loud valve lifter tick, and oil pressure starts dropping to about 75 from 85 nominal at 3500rpm.

This seems a little excessive for me. I also notice that when I go into boost on the highway I get a fairly large puff of black smoke. I haven't seen any blue in the mirror yet.

Also I am noticing a bit of oil sweating under the engine when it's parked but I don't notice any oil on the driveway.

 

[DSM1G90]

Check your PCV valve system.

a clogged up PCV valve will cause excessive oil consumption and it will not blue out the tail pipe along with potential danger of blowing out your crank main seals due to excessive crankcase pressure. The PCV system is really working on highway conditions.

Outside of that, you could have tired oil rings letting oil go past them under highway speed conditions due to the higher oil pressure and vacuum where you wont notice this when doing town driving and the motor isn't working very hard at all.

Both conditions are areas to probe into along with other factors that needs attention.

good luck - DSM