I’m buying a 1990 Toyota 4Runner from a FoaF, it has the 3.0 4-cylinder in it.
The engine was recently rebuilt.
The biggest problem I find on the web about it is that this engine model was subject to sludge-buildup problems.
Is there a way to reduce this problem?
Use oly low sludge lubricants of proper viscosity.
Change only when hot and at the reccemmended milage.
The 4Runner came with a 2.4L 4 cylinder or a 3.0 V-6. I have a 2.4L in my Toyota pickup and have never had a sludge problem with it. All I have ever used is Mobil 1.
I bought a Camry from that era for one of my nephews. Later research showed that some of the Toyota’s were prone to sludge buildup. IIRC, Toyota offers little-publicized extended coverage for that particular problem, in many models of that vintage.
IIRC, the sludge problem came about when the engine was redesigned to run a little hotter due to emmissions concerns.
This is an issue with “1MZ V-6 and 5SFE inline-4 engines produced between July 1996 and July 2001.” [1]
I believe the 3.0 in your 1990 model is NOT effected.
You do not have the issue you are concerned about.
Even if you do, STRICT adherence to 3,000 mile oil changes on name-brand API SM 5W30 will protect you, as will 5,000 mile oil changes on Mobil 1 or any motor oil meeting GM’s 4718M spec.
The big culprit in sludge buildup is water vapor in the oil. Mobil 1 is inherently resistant to the problem, IIRC. The best way to avoid the issue is to be sure the engine reaches full operating temperature when used. Short trips to the grocery store are the worst. I’d rather buy a car with 100,000 miles that was used to commute 100 miles a day for 4 years than the same car with 20,000 miles.
Running an engine involves a lot of air, and the water vapor in the air, passing through the engine. Some of that water vapor stays behind, and will eventually mix with the oil. If the engine parts get hot enough, the water vapor boils off before it can bind with the oil. This takes a good 10-20 miles of driving – 15 minutes of operation at least.
With all respect, the problem with this Toyota is that there’s a VERY HOT slow-flowing passage in the path of its oil.
As soon as the passage in question was widened with the redesign, the problem went away.
The issue of oil contamination from water condensation is a very real one, but NOT one that is pertinent with these Toyotas.