If this has just started suddenly then it is hard to see how a valve stem oil seal would be the culprit. I just don't how they fail all of a sudden.
On my '94, if I drove her hard - 75mph+ the oil that is pumped to the valve cover didn't have time to drain down from the baffles and was vacuumed up by the PHH. The first time this happened to me I burned through a quart between Orlando to Jacksonville. When I kept the speed below 65 mph she new burned a drop of oil.
Ironically, a heavier oil will make this worse.
Here is more information that most want - the PCV system was pretty clean as part of dress CEL 71.
The Landcruiser in question is a 1994 80 Series with a bit over 239,000 miles. It is a one owner car (my dad) and I have 90%+ of the service records since new. I characterize the maintenance as mostly by the book but light on PM. For example, the birfields were never done (until this spring) but always kept full. The basic life of the car was a 140 mile each way trip to a cabin in the mountains for which the last 5 miles could required chains and 4W low to get out of mud or snow. It was also used to drag dead trees around for firewood. Nothing huge. It has towed a 2,000 pound trailer once DC-Atlanta.
It has seen 28,000 miles use in the last 8 years since the cabin was sold an my folks mov to a retirement community. Much of that mileage is my daughter’s use when she comes for activities as a competitive rock climber.
15 months ago he made a decision to hand the car to my daughter. She agreed to take it. An October 2023 incident which ultimately turned out to be a failed harmonic balancer 7 months later got us on a change all the rubber and do the birfields program which was mostly done late last winter. It has had 3,000 miles since any engine work and 2,000 since the axels were done in anticipation of this trip.
Historically all oil changes were Mobile 1 FS 5w-30. The last two were Valvoline 5w-40 Syn Blend and then the current Mobile 1 FS 5w-40. When the was taken out, the mechanic reported at my request that 7.5 quarts came out after 4,900 miles. We do watch this stuff. Toyota filters since 2017.
I decided to “extend” this oil change as the 5,000 mile mark came on the 1,700 mile trip. At 237,000 miles I found the oil pressure sender (Std. Auto) put in as part of the Harmonic Balancer debacle was leaking at the crimp. It was replaced and I tope up th oil with 0.5qt that I wrote off to the leak. That is the last oil added until this 4-day 1,700 mile trip.
We do not drive this car over 75 and we tend to cruise at 72. I watch temps with a Toyobdi device
Day 1 330 miles, the oil was full ---- hard day through hills
Day 2 389 miles, the oil was full
Day 3 447 miles, the oil was just off the full line not much
Day 4 544 miles yesterday car teemp is 195-203 degees
@130 miles low oil light appears, pressure appears fine. Tempt is 203 degrees. I add a quart smoke pours out the back as I start up we drive to a T/A place 4 miles down the road and this all begins. Paid their mechanic to look it over, no coolant in the oil and no sign of oil in the expansion tank. The car is running perfectly. He sends me to Sinclair to buy oil for the balance of the trip – Sinclair blend 10w-40.
@180 miles I add 400 ml -we have slowed to 65mph but few options to highway
@279 miles I add 330 ml
@368 miles I add 330 ml
@511 miles I add 1 quart – at this point we are in rolling hills and I am doing a fair amount of on and off the gas.
Each fill was too the full mark, but I would not call conditions ideal an I clearly missed @511 miles
@551 miles and on a level spot and fully cooled it is clear I over shot adding a quart. The oil looks free of coolant. Looking at the coolant the level is what I expect but I perceive a slightly cloudy red versus the fresh jug of diluted coolant I carried as spare. Not certain.
Spark plug and compression readings in Nov. 24 – 20k miles on the plugs. Engine was warm an hour or so after a trip.
