Highlander oil use

I have a 2001 3.3 l AWD Highlander with 156k miles. On a 1500 mile trip last spring the car used 4 quarts of oil. Since then oil usage was normal. Just got back from a 2500 mile trip and used 6 quarts oil. No leaks. Other then one cold morning did not notice any blue exhaust. Car runs great. Any ideas? Thanks in advance for your efforts.

Check the PCV system for clogging. Check the valve, hoses and vacuum port.
Heavy oil use at steady high rpms could also be a ring problem.

Has your gasoline mileage changed for the worse? Years ago when we had carbureted engines the raw gasoline would dilute the oil. Around town, the oil consumption would appear to be normal. However, out on the highway, the diluted oil would burn off rather quickly and it wasnt unusual to have to add oil. This shouldn’t happen on modern fuel injected cars unless somehow raw gasoline is mixing with the oil because of faulty fuel injectors. However, I don’t think your engine would run very well if that is the case. What viscosity oil are using (10W-30, 5W-20, etc).
I did have a Ford Maverick that used quite a bit of oil until I had the valve stem seals replaced and went from one quart every 350 miles to one quart every 1250 miles. I don’t remember if the consumption became worse with highway driving or not. Before I replaced the valve stem seals I did have problems with spark plugs fouling out. However, you wouldn’t notice this on a modern car with a high voltage ignition as opposed to the mechanical breaker point ignition system on the Maverick.

Agreed, check the PCV first and hope. If the PCV is fine then it’s going to fall back onto the rings and/or valve seals.
A leakdown test could possibly help determine if the rings are at fault but there is no test for bad valve seals. Valve seals are a replace and hope repair.

I use 5W-30 motor oil (Valvoline). When I go on a long trip I do not check the MPG because I am driving 80 mph. My wife still can’t remember (or figureout) how to check fuel economy around town. If PVC is ok, is there any danger to the motor if I take a long trip 2 or 3 times a year and just add oil every gas top? Can I use a heavier weight oil while on a long rip? Thank you for your replies.

If the PCV SYSTEM checks out, I would indeed switch to 15w-40 fleet oil when running your Highlander at 80 mph…

I agree that a heavier oil could slow the oil consumption down.
If the problem is suspected to be valve seals you could try a conditioner which can soften and swell the seals a bit. It’s not a guarantee of a fix but won’t hurt anything to try.

If the problem is piston rings it’s often the oil control rings, or wiper rings as they’re called. They seize in the piston ring land (groove) and usually seize due to a past overheating episode or oil coking. (coked oil is basically hardened, burnt engine oil)
There is no cure for seized rings due to overheating but an additive such as SeaFoam, Rislone, or whatever may help to break some of the grunge loose in a coked oil situation and free the rings up.
Again, no guarantee of a fix but it won’t hurt to try.

I would also point out that if the engine has had any overheating spells in the past this can often ruin valve seals by hardening the rubber and/or cracking it. In this case, an additive likely won’t help.
It’s also possible to run a compression test, have good compression, and still have a problem with seized wiper rings so even that test is not a 100% certainty.

The engine temp has never above the normal range. I will look at the PCV and do some research before using any additves to see which is best. If PCV is not the problem and additives do not help, is there a problem running long distances if I keep proper oil level? I love this car, runs great and has been maintenance free. Would like to try and get 300K. Thanks again.

I had one thought about the oil usage on trips. Are you checking the oil when you stop for gas and are you allowing a few minutes for the oil to drain back into the oil pan? You may have only used a pint of oil, but if all the oil hasn’t drained back into the oil pan, it may appear as though you have consumed a quart. Around town, you may be checking the oil when the engine has been off for a while and the oil has all drained back into the oil pan.

I am allowing the oil to drain back before I check it. I just had the car in the shop for brake work and they checked the PCV and it does not leak. Mechanics there said oil rings or valve seals most likely leaking by. They said the only problem of running that way is that the catalytic converter would get ruined. I would like to get another 2 years (40k miles) more by just adding oil when needed. I am thinking of using a 15w-40 uring winter and long trips and 10w-40 during cold weather driving.

The mechanics are correct about the converter clogging up with coked oil. While the oil consumption is pretty heavy on the road I would say that it’s quite possible you could coax this thing along for 40k miles.
When it gets bad enough to really worry about you should notice a hesitation on acceleration, sluggish engine, etc.

You could try running a can of SeaFoam or something like that through the intake now and then. It could cut at least some of the burnt oil out of the converter.
And if you do try SeaFoam don’t be alarmed over the smoke cloud. That’s normal and will clear up shortly.

One more off-the-wall idea: If you have a tachometer, what is the reading at 80 mph? The reason I ask is that I wonder if the transmission is either slipping or not going into top gear. You said that the oil consumption is normal except on trips.
I once had an AMC Javelin with the 6 cylinder engine. I bought the car second hand and it seemed fine until we took a trip. Driving across Iowa on the interstate, I had the accelerator almost to the floorboard to maintain 75 mph. When we made a gas stop, the mileage was down to 14 mpg and the car needed a quart of oil. My wife had watched the mile markers and had noted the time when we entered Iowa. She calculated that we averaged 81 mph. I didn’t think this could be until I remembered that I had purchased some used tires that were two sizes bigger than what was on the car. This slowed down the speedometer and I think we were running the engine at practically full throttle. I remember my wife commenting on how slowly the Greyhound buses were traveling in Iowa. If your Highlander engine is running at high rpm for some reason, this might explain the oil usage on the highway. When I figured out the problem on the Javelin and drove at what I believed to be the posted speed limit, the mileage went up to 20 mpg and I didn’t need to add oil.